sound

sound¹

S0576500 (sound)n.1. a. Vibrations transmitted through an elastic solid or a liquid or gas, with frequencies in the approximate range of 20 to 20,000 hertz, capable of being detected by human organs of hearing.b. Transmitted vibrations of any frequency.c. The sensation stimulated in the organs of hearing by such vibrations in the air or other medium.d. Such sensations considered as a group.2. A distinctive noise: a hollow sound.3. The distance over which something can be heard: within sound of my voice.4. Linguistics a. An articulation made by the vocal apparatus: a vowel sound.b. The distinctive character of such an articulation: The words bear and bare have the same sound.5. A mental impression; an implication: didn't like the sound of the invitation.6. Auditory material that is recorded, as for a movie.7. Meaningless noise.8. Music A distinctive style, as of an orchestra or singer.9. Archaic Rumor; report.v. sound·ed, sound·ing, sounds v.intr.1. a. To make or give forth a sound: The siren sounded.b. To be given forth as a sound: The fanfare sounded.2. To present a particular impression: That argument sounds reasonable.v.tr.1. To cause to give forth or produce a sound: sounded the gong.2. To summon, announce, or signal by a sound: sound a warning.3. Linguistics To articulate; pronounce: sound a vowel.4. To make known; celebrate: "Nations unborn your mighty names shall sound" (Alexander Pope).5. To examine (a body organ or part) by causing to emit sound; auscultate.Phrasal Verb: sound off1. To express one's views vigorously: was always sounding off about higher taxes.2. To count cadence when marching in military formation.

[Middle English soun, from Old French son, from Latin sonus; see swen- in Indo-European roots.]

sound²

S0576500 (sound)adj. sound·er, sound·est 1. Free from defect, decay, or damage; in good condition: Is the bridge sound?2. Free from disease or injury. See Synonyms at healthy.3. a. Marked by or showing common sense and good judgment; levelheaded: a sound approach to the problem.b. Based on valid reasoning; having no logical flaws: a sound conclusion; sound reasoning. See Synonyms at valid.c. Logic Of or relating to an argument in which all the premises are true and the conclusion follows from the premises.4. a. Secure or stable: a partnership that started on a sound footing.b. Financially secure or safe: a sound economy.5. Thorough; complete: gave their rivals a sound thrashing.6. Deep and unbroken; undisturbed: a sound sleep.7. Compatible with an accepted point of view; orthodox: sound doctrine.adv. Thoroughly; deeply: sound asleep.

[Middle English, from Old English gesund.]

sound′ly adv.sound′ness n.

sound³

S0576500 (sound)n.1. Abbr. Sd.a. A long, relatively wide body of water, larger than a strait or a channel, connecting larger bodies of water.b. A long, wide ocean inlet.2. Archaic The swim bladder of a fish.

[Middle English, from Old English sund, swimming, sea.]

sound⁴

S0576500 (sound)v. sound·ed, sound·ing, sounds v.tr.1. To measure the depth of (water), especially by means of a weighted line; fathom.2. To try to learn the attitudes or opinions of: sounded out her feelings.3. To probe (a body cavity) with a sound.v.intr.1. To measure depth.2. To dive swiftly downward. Used of a marine mammal or a fish.3. To look into a possibility; investigate.n. An instrument used to examine or explore body cavities, as for foreign bodies or other abnormalities, or to dilate strictures in them.

[Middle English sounden, from Old French sonder, from sonde, sounding line, probably of Germanic origin.]

sound′a·ble adj.

sound

(saʊnd) n1. (General Physics) a. a periodic disturbance in the pressure or density of a fluid or in the elastic strain of a solid, produced by a vibrating object. It has a velocity in air at sea level at 0°C of 331 metres per second (741 miles per hour) and travels as longitudinal wavesb. (as modifier): a sound wave. 2. (Broadcasting) (modifier) of or relating to radio as distinguished from television: sound broadcasting; sound radio. 3. (Physiology) the sensation produced by such a periodic disturbance in the organs of hearing4. anything that can be heard5. a particular instance, quality, or type of sound: the sound of running water. 6. volume or quality of sound: a radio with poor sound. 7. the area or distance over which something can be heard: to be born within the sound of Big Ben. 8. the impression or implication of something: I don't like the sound of that. 9. (Phonetics & Phonology) phonetics the auditory effect produced by a specific articulation or set of related articulations10. (Jazz) (often plural) slang music, esp rock, jazz, or popvb11. to cause (something, such as an instrument) to make a sound or (of an instrument, etc) to emit a sound12. to announce or be announced by a sound: to sound the alarm. 13. (intr) (of a sound) to be heard14. (intr) to resonate with a certain quality or intensity: to sound loud. 15. (copula) to give the impression of being as specified when read, heard, etc: to sound reasonable. 16. (tr) to pronounce distinctly or audibly: to sound one's consonants. 17. (Law) law (usually foll by: in) to have the essential quality or nature (of): an action sounding in damages. [C13: from Old French soner to make a sound, from Latin sonāre, from sonus a sound] ˈsoundable adj

sound

(saʊnd) adj1. free from damage, injury, decay, etc2. firm; solid; substantial: a sound basis. 3. (Banking & Finance) financially safe or stable: a sound investment. 4. showing good judgment or reasoning; sensible; wise: sound advice. 5. valid, logical, or justifiable: a sound argument. 6. holding approved beliefs; ethically correct; upright; honest7. (of sleep) deep; peaceful; unbroken8. thorough; complete: a sound examination. 9. informal Brit excellent10. (Law) law (of a title, etc) free from defect; legally valid11. constituting a valid and justifiable application of correct principles; orthodox: sound theology. 12. (Logic) logic a. (of a deductive argument) validb. (of an inductive argument) according with whatever principles ensure the high probability of the truth of the conclusion given the truth of the premisesc. another word for consistent^5badvsoundly; deeply: now archaic except when applied to sleep[Old English sund; related to Old Saxon gisund, Old High German gisunt] ˈsoundly adv ˈsoundness n

sound

(saʊnd) vb1. (Navigation) to measure the depth of (a well, the sea, etc) by lowering a plumb line, by sonar, etc2. to seek to discover (someone's views, etc), as by questioning3. (Zoology) (intr) (of a whale, etc) to dive downwards swiftly and deeply4. (Medicine) med a. to probe or explore (a bodily cavity or passage) by means of a soundb. to examine (a patient) by means of percussion and auscultationn (Surgery) med an instrument for insertion into a bodily cavity or passage to dilate strictures, dislodge foreign material, etc[C14: from Old French sonder, from sonde sounding line, probably of Germanic origin; related to Old English sundgyrd sounding pole, Old Norse sund strait, sound⁴; see swim]

sound

(saʊnd) n1. (Physical Geography) a relatively narrow channel between two larger areas of sea or between an island and the mainland2. (Physical Geography) an inlet or deep bay of the sea3. (Zoology) the air bladder of a fish[Old English sund swimming, narrow sea; related to Middle Low German sunt strait; see sound³]

Sound

(saʊnd) n (Placename) the Sound a strait between SW Sweden and Zealand (Denmark), linking the Kattegat with the Baltic: busy shipping lane; spanned by a bridge in 2000. Length of the strait: 113 km (70 miles). Narrowest point: 5 km (3 miles). Danish name: Øresund Swedish name: Öresund

sound¹

(saʊnd)

n. 1. the sensation produced by stimulation of the organs of hearing by vibrations transmitted through the air or other medium. 2. mechanical vibrations transmitted through an elastic medium, traveling in air at a speed of approximately 1087 ft. (331 m) per second at sea level and at other speeds in other media. 3. the particular auditory effect produced by a given source: the sound of fire engines. 4. a noise, vocal utterance, musical tone, or the like: the sounds from the next room. 5. a distinctive, characteristic, or recognizable musical style: the Motown sound. 6. a. speech sound. b. the audible result of an articulation, utterance, or part of an utterance: the th-sound in there. 7. the auditory effect of sound waves as transmitted or recorded by a particular system of sound reproduction. 8. the quality of an event, letter, etc., as it affects a person: I don't like the sound of that report. 9. the distance within which something can be heard. 10. meaningless noise: all sound and fury. 11. Archaic. a report or rumor. v.i. 12. to make or emit a sound. 13. to give forth a signal, as a call or summons. 14. to convey a certain impression when heard or read: His voice sounded strange. 15. to give a specific sound: to sound loud. 16. to appear; seem: The report sounds true. v.t. 17. to cause to sound: Sound the alarm. 18. to give forth (a sound): The oboe sounded an A. 19. to announce or order by a sound: The bugle sounded retreat. 20. to utter audibly; pronounce: to sound each letter. 21. to examine by percussion or auscultation: to sound a patient's chest. 22. sound off, Informal. a. to call out one's name, as at military roll call. b. to call out the cadence as one marches in formation. c. to speak frankly or indiscreetly. d. to exaggerate; boast. [1250–1300; (n.) Middle English soun < Anglo-French (Old French son) < Latin sonus; (v.) Middle English sounen < Old French suner < Latin sonāre, derivative of sonus] sound′a•ble, adj.

sound²

(saʊnd)

adj. -er, -est,
adv. adj. 1. free from injury, damage, defect, disease, etc.; in good condition; healthy; robust: a sound body. 2. financially strong, secure, or reliable: a sound investment. 3. competent, sensible, or valid: sound judgment. 4. of substantial or enduring character: sound moral values. 5. having a logical basis: sound reasoning. 6. uninterrupted and untroubled; deep: sound sleep. 7. vigorous, thorough, or severe: a sound thrashing. 8. upright; honorable. 9. having no legal defect: a sound title to the property. adv. 10. deeply; thoroughly: sound asleep. [1150–1200; Middle English sund, Old English gesund (see y-); c. Dutch gezond, German gesund] sound′ly, adv. sound′ness, n.

sound³

(saʊnd)

v.t. 1. to measure or try the depth of (water, a deep hole, etc.) by letting down a lead or plummet at the end of a line, or by some equivalent means. 2. to measure (depth) in such a manner, as at sea. 3. to examine or test (the bottom, as of the sea or a deep hole) with a lead that brings up adhering bits of matter. 4. to seek to ascertain: to sound a person's views. 5. to attempt to elicit the views of (a person) by indirect inquiries (often fol. by out): Sound her out about working for us. v.i. 6. to use the lead and line or some other device for measuring depth, as at sea. 7. to go down or touch bottom, as a lead. 8. to plunge downward or dive, as a whale. 9. to seek information, esp. by indirect inquiries. [1300–50; Middle English sounden < Old French sonder to plumb, derivative of sonde sounding line] sound′a•ble, adj.

sound⁴

(saʊnd)

n. 1. a relatively narrow passage of water between larger bodies of water or between the mainland and an island: Long Island Sound. 2. an inlet, arm, or recessed portion of the sea: Puget Sound. 3. the air bladder of a fish. [before 900; Middle English; Old English sund swimming, sea, c. Old Norse sund; akin to swim]

Sound

(saʊnd)

n. The, English name of Øresund.

sound¹

(sound)1. A type of wave motion that originates as the vibration of a medium (such as a person's vocal cords or a guitar string) and travels through gases, liquids, and elastic solids as variations of pressure and density. The loudness of a sound depends on the amplitude of the sound wave. The pitch depends on its frequency.2. The sensation produced in the organs of hearing by waves of this type. See Note at ultrasound.Did You Know? The form of energy called sound is produced when matter moves or vibrates. The vibrations are transferred to another medium, usually the air, and travel through it as sound waves. You hear a sound when its vibrations reach your eardrum, causing it to vibrate. The pitch of a sound is directly related to the frequency of the vibrations of its waves. People with excellent hearing can hear very low sounds, vibrating about 20 times per second, all the way up to high pitches with frequencies of 20,000 vibrations per second. Other animals can hear sounds at higher vibrations. Bats, for instance, can hear sounds with vibrations as high as 100,000 times a second. The loudness, or intensity, of sound is measured in decibels. For each increase of 10 decibels, the sound wave has 10 times as much energy. For example, a sound of 20 decibels is twice as loud as one of 10 decibels, but has 10 times the energy. The softest sound humans can hear, at the very threshold of hearing, has a loudness of 0 decibels. A moderate conversation has a loudness of about 60 decibels, and thunder at very close range has a loudness of about 140 decibels. Sound with intensity greater than 85 decibels can cause ear damage, and sound with intensity above 120 decibels causes pain.

sound²

1. A long body of water, wider than a strait, that connects larger bodies of water.2. A long, wide inlet of the ocean, often parallel to the coast. Long Island Sound, between Long Island and the coast of New England, is an example.

Sound

See also hearing; language; music; pronunciation; songs and singing; speech; thunder.
acoustics1. Physics. the study of sound and sound waves.
2. the qualities or characteristics of a space, as an auditorium, that deter-mine the audibility and fidelity of sounds in it. — acoustician, n. — acoustic, adj.anacampticsObsolete, the study of the reflection of sounds. — anacamptic, adj.assonancelikeness or approximate similarity in sound.bombilationRare. a rumbling sound.bombinationRare. a buzzing or humming sound.cacophony1. a harshness of sound.
2. discordant noise. — cacophonic, cacophonous, adj.crepitationa crackling sound.diacousticsRare. the science of sounds refracted through various media.echolocationthe fixing of the position of an object by transmitting a signal and measuring the time required for it to bounce back, typically done by radar or sonar and by bats.echometrythe measurement of the duration of and intervals between sounds. — echometer, n.euphony1. an agreeableness in sounds; a pleasantness to the ear; harmoniousness.
2. Phonetics. a harmoniousness in speech sounds, especially in word choices emphasizing various patterns of consonants or vowels. — euphonic, euphonical, euphonious, adj.harmonometeran instrument for measuring the relationships between sounds.homonymythe state or quality of sounding identical, whether spelled identically or not, as bear and bare.homophonythe state or condition of a letter, word, or symbol having the same sound as another but a different meaning, regardless of sameness or difference in spelling, as choirlquire. — homophonic, homophonous, adj.kaleidophon, kaleidophonean instrument for the visual representation of sound waves.monotonydullness or uniformity, similar to that experienced from a repeated sound. — monotonous, adj.onomatopoeiathe state or condition of a word formed to imitate the sound of its intended meaning, as rustle. — onomatopoeic, onomatopoetic, onoma-topoietic, onomatopoeial, adj.oxyphonia, oxyphonyan unusually sharp quality or pitch of sound or voice.phonology1. the study of speech sounds, from either or both the phonetic and phonemic viewpoints.
2. the phonetic and phonemic systems of a language. See also linguistics. — phonologist, n. — phonological, adj.phonomaniaan abnormal love of noise.phonophobiaan abnormal f ear of noise.plangencythe condition or quality of producing a deep or loud sound. — plangent, adj.psychoacousticsthe study of the relationship between sounds and their perception by the listener, especially with regard to how the perception depends on the physical characteristics of the sound rather than on the mind of the listener. — psychoacoustician, n. — psychoacoustic, adj.raucitythe state or quality of sounding hoarse or harsh. — raucous, adj.sibilancy, sibilancethe state or quality of a hissing sound. — sibilant, adj.stridulation1. the producing of a shrill, grating noise by chafing a serrated part of the body against a hard part.
2. the noise so produced. — stridulator, n. — stridulant, stridulatory, adj.susurration1. the act or process of whispering.
2. a whispering sound or soft rustling. Also susurrus. — susurrant, susurrous, adj.tautophonyrepetition of the same sound. — tautophonic, tautophonical, adj.ultrasonicsthe science or study of ultrasonic vibrations, those belonging to a frequency above the audio range. — ultrasonic, adj.ululation1. the act of wailing or hooting.
2. the sound thus produced. — ululant, adj.

sound

1. 'sound'

You use sound as a verb in front of an adjective phrase when you are describing something that you hear.

The helicopter sounded worryingly close.The piano sounds really beautiful.

You can also use sound in front of an adjective phrase to describe the impression you have of someone when they speak.

José sounded a little disappointed.I don't know where she comes from, but she sounds foreign.

You also use sound to describe the impression you have of someone or something that you have just heard about or read about.

'They have a little house in the mountains.' 'That sounds nice.'The instructions sound a bit complicated.

Be Careful!
Don't use a progressive form. Don't say, for example, 'That is sounding nice'.

Be Careful!
Sound is followed by an adjective, not an adverb. Don't say 'That sounds nicely'.

2. 'sound like'

You can use sound like and a noun phrase to say that something has a similar sound to something else.

The bird's call sounds like a whistle.Her footsteps sounded like pistol shots.

You can also use sound like and a noun phrase to say that someone is talking the way another person usually talks.

He sounded like a little boy being silly.Stop telling me what to do you sound just like my mother.

You can use sound like and a noun phrase to say that you think you can recognize what something is, because of its sound.

They were playing a piece that sounded like Mozart.Someone left a message it sounded like your husband.

You can also use sound like and a noun phrase to express an opinion about something that someone has just described to you.

That sounds like a lovely idea.It sounds like something we should seriously consider.

sound

noise">noise1. used as countable nouns

A sound is something that you can hear. A noise is an unpleasant or unexpected sound. You say that machinery makes a noise. People and animals can also make noises.

A sudden noise made Bela jump.The birds were making screeching noises.2. used as uncountable nouns

Sound and noise can both be uncountable nouns.

Sound is the general term for what you hear as a result of vibrations travelling through the air, water, etc.

The aircraft could go faster than the speed of sound.

Be Careful!
When you use sound with this meaning, don't say 'the sound'.

Don't use expressions such as 'much' or 'a lot of' with sound. Don't say, for example, 'There was a lot of sound'. Say 'There was a lot of noise'.

Is that the wind making all that noise?Try not to make so much noise.

sound

Past participle: sounded
Gerund: sounding

Imperative
sound
sound

Present
I sound
you sound
he/she/it sounds
we sound
you sound
they sound

Preterite
I sounded
you sounded
he/she/it sounded
we sounded
you sounded
they sounded

Present Continuous
I am sounding
you are sounding
he/she/it is sounding
we are sounding
you are sounding
they are sounding

Present Perfect
I have sounded
you have sounded
he/she/it has sounded
we have sounded
you have sounded
they have sounded

Past Continuous
I was sounding
you were sounding
he/she/it was sounding
we were sounding
you were sounding
they were sounding

Past Perfect
I had sounded
you had sounded
he/she/it had sounded
we had sounded
you had sounded
they had sounded

Future
I will sound
you will sound
he/she/it will sound
we will sound
you will sound
they will sound

Future Perfect
I will have sounded
you will have sounded
he/she/it will have sounded
we will have sounded
you will have sounded
they will have sounded

Future Continuous
I will be sounding
you will be sounding
he/she/it will be sounding
we will be sounding
you will be sounding
they will be sounding

Present Perfect Continuous
I have been sounding
you have been sounding
he/she/it has been sounding
we have been sounding
you have been sounding
they have been sounding

Future Perfect Continuous
I will have been sounding
you will have been sounding
he/she/it will have been sounding
we will have been sounding
you will have been sounding
they will have been sounding

Past Perfect Continuous
I had been sounding
you had been sounding
he/she/it had been sounding
we had been sounding
you had been sounding
they had been sounding

Conditional
I would sound
you would sound
he/she/it would sound
we would sound
you would sound
they would sound

Past Conditional
I would have sounded
you would have sounded
he/she/it would have sounded
we would have sounded
you would have sounded
they would have sounded

sound

The phenomenon produced by certain pressure waves reaching the ear.

Thesaurus

Noun	1.	sound - the particular auditory effect produced by a given cause; "the sound of rain on the roof"; "the beautiful sound of music"noisiness, racketiness - the auditory effect characterized by loud and constant noisering - a characteristic sound; "it has the ring of sincerity"unison - (music) two or more sounds or tones at the same pitch or in octaves; "singing in unison"voice - the distinctive quality or pitch or condition of a person's speech; "A shrill voice sounded behind us"sound property - an attribute of soundsilence, quiet - the absence of sound; "he needed silence in order to sleep"; "the street was quiet"
	2.	sound - the subjective sensation of hearing something; "he strained to hear the faint sounds"auditory sensationaesthesis, esthesis, sensation, sense datum, sense experience, sense impression - an unelaborated elementary awareness of stimulation; "a sensation of touch"euphony, music - any agreeable (pleasing and harmonious) sounds; "he fell asleep to the music of the wind chimes"music - (music) the sounds produced by singers or musical instruments (or reproductions of such sounds)pure tone, tone - a steady sound without overtones; "they tested his hearing with pure tones of different frequencies"dissonance, noise, racket - the auditory experience of sound that lacks musical quality; sound that is a disagreeable auditory experience; "modern music is just noise to me"dub - the new sounds added by dubbing
	3.	sound - mechanical vibrations transmitted by an elastic medium; "falling trees make a sound in the forest even when no one is there to hear them"mechanical phenomenon - a physical phenomenon associated with the equilibrium or motion of objectsultrasound - very high frequency sound; used in ultrasonography
	4.	sound - the sudden occurrence of an audible event; "the sound awakened them"happening, natural event, occurrence, occurrent - an event that happensbong - a dull resonant sound as of a bellbeat - the sound of stroke or blow; "he heard the beat of a drum"beep, bleep - a short high tone produced as a signal or warningbell, toll - the sound of a bell being struck; "saved by the bell"; "she heard the distant toll of church bells"bombilation, bombination, buzz - sound of rapid vibration; "the buzz of a bumble bee"click, clink, chink - a short light metallic soundchirp - a sharp sound made by small birds or insectschirrup, twitter - a series of chirpschorus - any utterance produced simultaneously by a group; "a chorus of boos"click-clack - a succession of clicksclip-clop, clippety-clop, clop, clopping, clumping, clunking - the sound of a horse's hoofs hitting on a hard surfacecry - the characteristic utterance of an animal; "animal cries filled the night"ding - a ringing sounddrip, dripping - the sound of a liquid falling drop by drop; "the constant sound of dripping irritated him"drum - the sound of a drum; "he could hear the drums before he heard the fifes"footfall, footstep, step - the sound of a step of someone walking; "he heard footsteps on the porch"gargle - the sound produced while garglinggurgle - the bubbling sound of water flowing from a bottle with a narrow neckjangle, jingle - a metallic sound; "the jingle of coins"; "the jangle of spurs"knock, knocking - the sound of knocking (as on a door or in an engine or bearing); "the knocking grew louder"murmur, murmuration, murmuring, mussitation, mutter, muttering - a low continuous indistinct sound; often accompanied by movement of the lips without the production of articulate speechnoise - sound of any kind (especially unintelligible or dissonant sound); "he enjoyed the street noises"; "they heard indistinct noises of people talking"; "during the firework display that ended the gala the noise reached 98 decibels"drum roll, paradiddle, roll - the sound of a drum (especially a snare drum) beaten rapidly and continuouslypat, tap, rap - the sound made by a gentle blowpatter - a quick succession of light rapid sounds; "the patter of mice"; "the patter of tiny feet"peal, pealing, rolling, roll - a deep prolonged sound (as of thunder or large bells)ping - a sharp high-pitched resonant sound (as of a sonar echo or a bullet striking metal)plunk - a hollow twanging soundpopping, pop - a sharp explosive sound as from a gunshot or drawing a corkpurr - a low vibrating sound typical of a contented catquack - the harsh sound of a duckquaver - a tremulous soundringing, tintinnabulation, ring - the sound of a bell ringing; "the distinctive ring of the church bell"; "the ringing of the telephone"; "the tintinnabulation that so voluminously swells from the ringing and the dinging of the bells"--E. A. Poedrumbeat, rataplan, rub-a-dub - the sound made by beating a drumsigh - a sound like a person sighing; "she heard the sigh of the wind in the trees"skirl - the sound of (the chanter of) a bagpipesong - a distinctive or characteristic sound; "the song of bullets was in the air"; "the song of the wind"; "the wheels sang their song as the train rocketed ahead"strum - sound of strumming; "the strum of a guitar"susurration, susurrus - the indistinct sound of people whispering; "a soft susurrus of conversation"swish - a brushing or rustling soundtapping - the sound of light blow or knock; "he heard the tapping of the man's cane"throbbing - a sound with a strong rhythmic beat; "the throbbing of the engines"clunk, thud, thump, thumping, clump - a heavy dull sound (as made by impact of heavy objects)thrum - a thrumming sound; "he could hear the thrum of a banjo"thunk - a dull hollow sound; "the basketball made a thunk as it hit the rim"tick, ticking - a metallic tapping sound; "he counted the ticks of the clock"ting, tinkle - a light clear metallic sound as of a small belltoot - a blast of a horntootle - the sound of casual playing on a musical instrument; "he enjoyed hearing the tootles of their horns as the musicians warmed up"
	5.	sound - the audible part of a transmitted signal; "they always raise the audio for commercials"audiotelecasting, television, TV, video - broadcasting visual images of stationary or moving objects; "she is a star of screen and video"; "Television is a medium because it is neither rare nor well done" - Ernie Kovacsauditory communication - communication that relies on hearing
	6.	sound - (phonetics) an individual sound unit of speech without concern as to whether or not it is a phoneme of some languagespeech sound, phonephonetics - the branch of acoustics concerned with speech processes including its production and perception and acoustic analysislanguage unit, linguistic unit - one of the natural units into which linguistic messages can be analyzedutterance, vocalization - the use of uttered sounds for auditory communicationphoneme - (linguistics) one of a small set of speech sounds that are distinguished by the speakers of a particular languagevowel, vowel sound - a speech sound made with the vocal tract openglide, semivowel - a vowellike sound that serves as a consonantconsonant - a speech sound that is not a vowelorinasal, orinasal phone - a speech sound produced with both the oral and nasal passages open (as French nasal vowels)sonant, voiced sound - a speech sound accompanied by sound from the vocal cords
	7.	sound - a narrow channel of the sea joining two larger bodies of waterstraitchannel - a deep and relatively narrow body of water (as in a river or a harbor or a strait linking two larger bodies) that allows the best passage for vessels; "the ship went aground in the channel"narrow - a narrow strait connecting two bodies of water
	8.	sound - a large ocean inlet or deep bay; "the main body of the sound ran parallel to the coast"body of water, water - the part of the earth's surface covered with water (such as a river or lake or ocean); "they invaded our territorial waters"; "they were sitting by the water's edge"
Verb	1.	sound - appear in a certain way; "This sounds interesting"appear, seem, look - give a certain impression or have a certain outward aspect; "She seems to be sleeping"; "This appears to be a very difficult problem"; "This project looks fishy"; "They appeared like people who had not eaten or slept for a long time"
	2.	sound - make a certain noise or sound; "She went `Mmmmm'"; "The gun went `bang'"gosnarl - make a snarling noise or move with a snarling noise; "Bullets snarled past us"sing, whistle - make a whining, ringing, or whistling sound; "the kettle was singing"; "the bullet sang past his ear"cause to be perceived - have perceptible qualitiesblow - make a sound as if blown; "The whistle blew"ting - make a light, metallic sound; go `ting'make noise, noise, resound - emit a noisesplat - give off the sound of a bullet flattening on impacttwang - sound with a twang; "the bowstring was twanging"clang, clangor - make a loud noise; "clanging metal"clank - make a clank; "the train clanked through the village"clangor, clangour - make a loud resonant noise; "the alarm clangored throughout the building"boom out, boom - make a deep hollow sound; "Her voice booms out the words of the song"drum, thrum, beat - make a rhythmic sound; "Rain drummed against the windshield"; "The drums beat all night"rattle - make short successive soundsticktack, ticktock, tick, beat - make a sound like a clock or a timer; "the clocks were ticking"; "the grandfather clock beat midnight"resonate, vibrate - sound with resonance; "The sound resonates well in this theater"crash - make a sudden loud sound; "the waves crashed on the shore and kept us awake all night"tweet, twirp - make a weak, chirping sound; "the small bird was tweeting in the tree"skirl - make a shrill, wailing sound; "skirling bagpipes"gurgle - make sounds similar to gurgling water; "The baby gurgled with satisfaction when the mother tickled it"glug - make a gurgling sound as of liquid issuing from a bottle; "the wine bottles glugged"blow - sound by having air expelled through a tube; "The trumpets blew"whish - make a sibilant soundguggle - make a sound like a liquid that is being poured from a bottleping - make a short high-pitched sound; "the bullet pinged when they struck the car"ping, pink, knock - sound like a car engine that is firing too early; "the car pinged when I put in low-octane gasoline"; "The car pinked when the ignition was too far retarded"trump - produce a sound as if from a trumpetsquelch - make a sucking soundchug - make a dull, explosive sound; "the engine chugged down the street"ring, peal - sound loudly and sonorously; "the bells rang"bombilate, bombinate, buzz - make a buzzing sound; "bees were buzzing around the hive"chime - emit a sound; "bells and gongs chimed"rustle - make a dry crackling sound; "rustling silk"; "the dry leaves were rustling in the breeze"crack, snap - make a sharp sound; "his fingers snapped"crack - make a very sharp explosive sound; "His gun cracked"beep, claxon, honk, toot, blare - make a loud noise; "The horns of the taxis blared"whistle - make whistling sounds; "He lay there, snoring and whistling"resound, reverberate, ring, echo - ring or echo with sound; "the hall resounded with laughter"thud, thump - make a dull sound; "the knocker thudded against the front door"clop, clump, clunk, plunk - make or move along with a sound as of a horse's hooves striking the groundpatter, pitter-patter - make light, rapid and repeated sounds; "gently pattering rain"pink, rap, knock, tap - make light, repeated taps on a surface; "he was tapping his fingers on the table impatiently"tick, click - make a clicking or ticking sound; "The clock ticked away"chatter, click - click repeatedly or uncontrollably; "Chattering teeth"pop - make a sharp explosive noise; "The cork of the champagne bottle popped"chink, tink, tinkle, clink - make or emit a high sound; "tinkling bells"slosh, slush, splosh, splash - make a splashing sound; "water was splashing on the floor"thrum, hum - sound with a monotonous humbleep - emit a single short high-pitched signal; "The computer bleeped away"rumble, grumble - make a low noise; "rumbling thunder"boom, din - make a resonant sound, like artillery; "His deep voice boomed through the hall"bang - to produce a sharp often metallic explosive or percussive sound; "One of them banged the sash of the window nearest my bed"
	3.	sound - give off a certain sound or sounds; "This record sounds scratchy"cackel - make a cackling sound; "The fire cackled cozily"play - emit recorded sound; "The tape was playing for hours"; "the stereo was playing Beethoven when I entered"dissonate - be dissonant or harsh; "The violins in this piece dissonated disturbingly"pierce - sound sharply or shrilly; "The scream pierced the night"speak - make a characteristic or natural sound; "The drums spoke"
	4.	sound - announce by means of a sound; "sound the alarm"announce, denote - make known; make an announcement; "She denoted her feelings clearly"
	5.	sound - utter with vibrating vocal chords vocalize, voice, vocaliseenounce, enunciate, pronounce, sound out, articulate, say - speak, pronounce, or utter in a certain way; "She pronounces French words in a funny way"; "I cannot say `zip wire'"; "Can the child sound out this complicated word?"chirk - make a shrill creaking, squeaking, or noise, as of a door, mouse, or birdquaver, waver - give off unsteady sounds, alternating in amplitude or frequency
	6.	sound - cause to sound; "sound the bell"; "sound a certain note"play - perform music on (a musical instrument); "He plays the flute"; "Can you play on this old recorder?"blow - play or sound a wind instrument; "She blew the horn"twang - cause to sound with a twang; "He twanged the guitar string"prepare - lead up to and soften by sounding the dissonant note in it as a consonant note in the preceding chord; "prepare the discord in bar 139"gong - sound a gongting - cause to make a tingstrum, thrum - sound the strings of (a string instrument); "strum a guitar"knell, ring - make (bells) ring, often for the purposes of musical edification; "Ring the bells"; "My uncle rings every Sunday at the local church"pop - cause to make a sharp explosive sound; "He popped the champagne bottle"clink - make a high sound typical of glass; "champagne glasses clinked to make a toast"strike up, sound off - start playing; "The musicians struck up a tune"
	7.	sound - measure the depth of (a body of water) with a sounding linefathommeasure, quantify - express as a number or measure or quantity; "Can you quantify your results?"
Adj.	1.	sound - financially secure and safe; "sound investments"; "a sound economy"unbroken - not broken; whole and intact; in one piece; "fortunately the other lens is unbroken"undamaged - not harmed or spoiled; soundfit - physically and mentally sound or healthy; "felt relaxed and fit after their holiday"; "keeps fit with diet and exercise"healthy - having or indicating good health in body or mind; free from infirmity or disease; "a rosy healthy baby"; "staying fit and healthy"uninjured - not injured physically or mentallywholesome - conducive to or characteristic of physical or moral well-being; "wholesome attitude"; "wholesome appearance"; "wholesome food"unsound - not sound financially; "unsound banking practices"
	2.	sound - exercising or showing good judgment; "healthy scepticism"; "a healthy fear of rattlesnakes"; "the healthy attitude of French laws"; "healthy relations between labor and management"; "an intelligent solution"; "a sound approach to the problem"; "sound advice"; "no sound explanation for his decision"levelheaded, level-headed, intelligent, healthyreasonable, sensible - showing reason or sound judgment; "a sensible choice"; "a sensible person"
	3.	sound - in good condition; free from defect or damage or decay; "a sound timber"; "the wall is sound"; "a sound foundation"unsound - not in good condition; damaged or decayed; "an unsound foundation"
	4.	sound - in excellent physical condition; "good teeth"; "I still have one good leg"; "a sound mind in a sound body"goodhealthy - having or indicating good health in body or mind; free from infirmity or disease; "a rosy healthy baby"; "staying fit and healthy"
	5.	sound - logically valid; "a sound argument"reasoned, well-groundedvalid - well grounded in logic or truth or having legal force; "a valid inference"; "a valid argument"; "a valid contract"
	6.	sound - having legal efficacy or force; "a sound title to the property"effectual, legalvalid - well grounded in logic or truth or having legal force; "a valid inference"; "a valid argument"; "a valid contract"
	7.	sound - free from moral defect; "a man of sound character"righteous - characterized by or proceeding from accepted standards of morality or justice; "the...prayer of a righteous man availeth much"- James 5:16
	8.	sound - (of sleep) deep and complete; "a heavy sleep"; "fell into a profound sleep"; "a sound sleeper"; "deep wakeless sleep"wakeless, profound, heavydeep - relatively deep or strong; affecting one deeply; "a deep breath"; "a deep sigh"; "deep concentration"; "deep emotion"; "a deep trance"; "in a deep sleep"
	9.	sound - thorough; "a sound thrashing"complete - having every necessary or normal part or component or step; "a complete meal"; "a complete wardrobe"; "a complete set of the Britannica"; "a complete set of china"; "a complete defeat"; "a complete accounting"

sound

¹noun1. noise, racket, din, report, tone, bang, resonance, hubbub, reverberation Peter heard the sound of gunfire.2. idea, prospect, impression, implication(s), drift Here's a new idea we like the sound of.3. cry, noise, peep, squeak She didn't make a sound.4. tone, music, note, chord, tenor the soulful sound of the violin5. earshot, hearing, hearing distance I was born and bred within the sound of the cathedral bells.verb1. toll, set off A young man sounds the bell to start the Sunday service.2. resound, echo, go off, toll, set off, chime, resonate, reverberate, ding, clang, peal A silvery bell sounded somewhere.3. express, declare, utter, announce, signal, pronounce, articulate, enunciate Others consider the move premature and have sounded a note of caution.4. seem, seem to be, appear to be, give the impression of being, strike you as being, give every indication of being She sounded a bit worried.Related words
adjective sonic, acoustic
fear akousticophobia

sound

²adjective1. fit, healthy, robust, firm, perfect, intact, vigorous, hale, unhurt, undamaged, uninjured, unimpaired, hale and hearty His body was still sound.
fit weak, ailing, frail, damaged, unstable, shaky2. sturdy, strong, solid, stable, substantial, durable, stout, well-constructed a perfectly sound building3. safe, secure, reliable, proven, established, recognized, solid, stable, solvent, reputable, tried-and-true a sound financial proposition
safe unreliable, unsound, unstable4. sensible, wise, reasonable, right, true, responsible, correct, proper, reliable, valid, orthodox, rational, logical, prudent, trustworthy, well-founded, level-headed, right-thinking, well-grounded They are trained nutritionists who can give sound advice on diets.
sensible irresponsible, faulty, irrational, specious, flawed, fallacious5. deep, peaceful, unbroken, undisturbed, untroubled She has woken me out of a sound sleep.
deep broken, troubled, fitful, shallow6. thorough, complete, total, severe, absolute, downright, unqualified, out-and-out, unmitigated a sound beatingQuotations
"a sound mind in a sound body" [Juvenal Satires]

sound

³ verbsound someone out question, interview, survey, poll, examine, investigate, pump (informal), inspect, canvass, test the opinion of Sound him out gradually.sound something out investigate, research, examine, probe, look into, test the water, put out feelers to, see how the land lies, carry out an investigation of They are discreetly sounding out blue-chip American banks.

sound

⁴noun channel, passage, strait, inlet, fjord, voe, arm of the sea a blizzard blasting great drifts of snow across the sound

sound¹

noun1. The sensation caused by vibrating wave motion that is perceived by the organs of hearing:noise, sonance.2. Range of audibility:earshot, hearing.verbTo have the appearance of:appear, look, seem.Idiom: strike one as (being).

sound²

adjective1. In excellent condition:entire, flawless, good, intact, perfect, unblemished, unbroken, undamaged, unharmed, unhurt, unimpaired, uninjured, unmarred, whole.2. Having good health:fit, hale, healthful, healthy, hearty, right, well, whole, wholesome.Idioms: fit as a fiddle, hale and hearty, in fine fettle.3. Not easily moved or shaken:firm, secure, solid, stable, strong, sturdy, substantial, sure, unshakable.4. Based on good judgment, reasoning, or evidence:cogent, just, solid, tight, valid, well-founded, well-grounded.5. Capable of being depended upon:dependable, reliable, responsible, solid, trustworthy, trusty.6. Possessing, proceeding from, or exhibiting good judgment and prudence:balanced, commonsensible, commonsensical, judicious, levelheaded, prudent, rational, reasonable, sagacious, sage, sane, sapient, sensible, well-founded, well-grounded, wise.

sound³

verbTo test the attitude of.Also used with out:feel out, probe.Idioms: put out feelers, send up a trial balloon.

Translations

声音完好的彻底的正确的测...深度

sound¹

(saund) adjective1. strong or in good condition. The foundations of the house are not very sound; He's 87, but he's still sound in mind and body. 健康的，完好的 2. (of sleep) deep. She's a very sound sleeper.酣睡的3. full; thorough. a sound basic training.彻底的4. accurate; free from mistakes. a sound piece of work.正确的5. having or showing good judgement or good sense. His advice is always very sound.合理的ˈsoundly adverb正确地ˈsoundness noun 坚定性，正当 sound asleep sleeping deeply. The baby is sound asleep.酣睡的

sound²

noun1. the impressions transmitted to the brain by the sense of hearing. a barrage of sound; (also adjective) sound waves.声2. something that is, or can be, heard. The sounds were coming from the garage.声音3. the impression created in the mind by a piece of news, a description etc. I didn't like the sound of her hairstyle at all!印象 verb1. to (cause something to) make a sound. Sound the bell!; The bell sounded.使...响2. to signal (something) by making a sound. Sound the alarm! 使发声，给出信号 3. (of something heard or read) to make a particular impression; to seem; to appear. Your singing sounded very good; That sounds like a train. （由听，读）而得到特别印象 4. to pronounce. In the word `pneumonia', the letter p is not sounded.发音5. to examine by tapping and listening carefully. She sounded the patient's chest.听诊和叩诊ˈsoundless adjective无声的ˈsoundlessly adverb无声地sound effects sounds other than dialogue or music, used in films, radio etc. 音响效果ˈsoundproof adjective not allowing sound to pass in, out, or through. The walls are soundproof.隔音的 verb to make (walls, a room etc) soundproof. 给...隔音ˈsound-track noun (a recording of) the music from a film. I've just bought the sound-track of that new film. 电影原声大碟，电影电视配乐

sound³

(saund) verb to measure the depth of (water etc). 测...深度ˈsounding noun1. (a) measurement of depth of water etc. 水深测量2. a depth measured. 测深3. (an) act of trying to find out views etc. 调查sound out to try to find out someone's thoughts and plans etc. Will you sound out your father on this? 试探意见，探听口气

sound

→ 声音zhCN, 良好的zhCN

sound

sound,

any disturbance that travels through an elastic medium such as air, ground, or water to be heard by the human ear. When a body vibrates, or moves back and forth (see vibrationvibration,
in physics, commonly an oscillatory motion—a movement first in one direction and then back again in the opposite direction. It is exhibited, for example, by a swinging pendulum, by the prongs of a tuning fork that has been struck, or by the string of a musical
..... Click the link for more information. ), the oscillation causes a periodic disturbance of the surrounding air or other medium that radiates outward in straight lines in the form of a pressure wavewave,
in physics, the transfer of energy by the regular vibration, or oscillatory motion, either of some material medium or by the variation in magnitude of the field vectors of an electromagnetic field (see electromagnetic radiation).
..... Click the link for more information. . The effect these waves produce upon the ear is perceived as sound. From the point of view of physics, sound is considered to be the waves of vibratory motion themselves, whether or not they are heard by the human ear.

Generation of Sound Waves

Sound waves are generated by any vibrating body. For example, when a violin string vibrates upon being bowed or plucked, its movement in one direction pushes the molecules of the air before it, crowding them together in its path. When it moves back again past its original position and on to the other side, it leaves behind it a nearly empty space, i.e., a space with relatively few molecules in it. In the meantime, however, the molecules which were at first crowded together have transmitted some of their energy of motion to other molecules still farther on and are returning to fill again the space originally occupied and now left empty by the retreating violin string. In other words, the vibratory motion set up by the violin string causes alternately in a given space a crowding together of the molecules of air (a condensation) and a thinning out of the molecules (a rarefaction). Taken together a condensation and a rarefaction make up a sound wave; such a wave is called longitudinal, or compressional, because the vibratory motion is forward and backward along the direction that the wave is following. Because such a wave travels by disturbing the particles of a material medium, sound waves cannot travel through a vacuum.

Characteristics of Sound Waves

Sounds are generally audible to the human ear if their frequency (number of vibrations per second) lies between 20 and 20,000 vibrations per second, but the range varies considerably with the individual. Sound waves with frequencies less than those of audible waves are called subsonic; those with frequencies above the audible range are called ultrasonic (see ultrasonicsultrasonics,
study and application of the energy of sound waves vibrating at frequencies greater than 20,000 cycles per second, i.e., beyond the range of human hearing. The application of sound energy in the audible range is limited almost entirely to communications, since
..... Click the link for more information. ).

A sound wave is usually represented graphically by a wavy, horizontal line; the upper part of the wave (the crest) indicates a condensation and the lower part (the trough) indicates a rarefaction. This graph, however, is merely a representation and is not an actual picture of a wave. The length of a sound wave, or the wavelength, is measured as the distance from one point of greatest condensation to the next following it or from any point on one wave to the corresponding point on the next in a train of waves. The wavelength depends upon the velocity of sound in a given medium at a given temperature and upon the frequency of vibration. The wavelength of a sound can be determined by dividing the numerical value for the velocity of sound in the given medium at the given temperature by the frequency of vibration. For example, if the velocity of sound in air is 1,130 ft per second and the frequency of vibration is 256, then the wave length is approximately 4.4 ft.

The velocity of sound is not constant, however, for it varies in different media and in the same medium at different temperatures. For example, in air at 0&degC;. it is approximately 1,089 ft per second, but at 20&degC;. it is increased to about 1,130 ft per second, or an increase of about 2 ft per second for every centigrade degree rise in temperature. Sound travels more slowly in gases than in liquids, and more slowly in liquids than in solids. Since the ability to conduct sound is dependent on the density of the medium, solids are better conductors than liquids, liquids are better conductors than gases.

Sound waves can be reflected, refracted (or bent), and absorbed as light waves can be. The reflection of sound waves can result in an echoecho,
reflection of a sound wave back to its source in sufficient strength and with a sufficient time lag to be separately distinguished. If a sound wave returns within 1-10 sec, the human ear is incapable of distinguishing it from the orginal one.
..... Click the link for more information. —an important factor in the acousticsacoustics
[Gr.,=the facts about hearing], the science of sound, including its production, propagation, and effects. Various branches of acoustics that deal with different aspects of sound and hearing include bioacoustics, physical acoustics, ultrasonics, and architectural
..... Click the link for more information. of theaters and auditoriums. A sound wave can be reinforced with waves from a body having the same frequency of vibration, but the combination of waves of different frequencies of vibration may produce "beats" or pulsations or may result in other forms of interferenceinterference,
in physics, the effect produced by the combination or superposition of two systems of waves, in which these waves reinforce, neutralize, or in other ways interfere with each other.
..... Click the link for more information. .

Characteristics of Musical Sounds

Musical sounds are distinguished from noises in that they are composed of regular, uniform vibrations, while noises are irregular and disordered vibrations. Composers, however, frequently use noises as well as musical sounds. One musical tone is distinguished from another on the basis of pitch, intensity, or loudness, and quality, or timbre. Pitch describes how high or low a tone is and depends upon the rapidity with which a sounding body vibrates, i.e., upon the frequency of vibration. The higher the frequency of vibration, the higher the tone; the pitch of a siren gets higher and higher as the frequency of vibration increases. The apparent change in the pitch of a sound as a source approaches or moves away from an observer is described by the Doppler effectDoppler effect,
change in the wavelength (or frequency) of energy in the form of waves, e.g., sound or light, as a result of motion of either the source or the receiver of the waves; the effect is named for the Austrian scientist Christian Doppler, who demonstrated the effect
..... Click the link for more information. . The intensity or loudness of a sound depends upon the extent to which the sounding body vibrates, i.e., the amplitude of vibration. A sound is louder as the amplitude of vibration is greater, and the intensity decreases as the distance from the source increases. Loudness is measured in units called decibelsdecibel
, abbr. dB, unit used to measure the loudness of sound. It is one tenth of a bel (named for A. G. Bell), but the larger unit is rarely used. The decibel is a measure of sound intensity as a function of power ratio, with the difference in decibels between two sounds being
..... Click the link for more information. . The sound waves given off by different vibrating bodies differ in quality, or timbre. A note from a saxophone, for instance, differs from a note of the same pitch and intensity produced by a violin or a xylophone; similarly vibrating reeds, columns of air, and strings all differ. Quality is dependent on the number and relative intensity of overtones produced by the vibrating body (see harmonicharmonic.
1 Physical term describing the vibration in segments of a sound-producing body (see sound). A string vibrates simultaneously in its whole length and in segments of halves, thirds, fourths, etc.
..... Click the link for more information. ), and these in turn depend upon the nature of the vibrating body.

Bibliography

See G. Chedd, Sound (1970).

Sound

The mechanical excitation of an elastic medium. Originally, sound was considered to be only that which is heard. This admitted questions such as whether or not sound was generated by trees falling where no one could hear. A more mechanistic approach avoids these questions and also allows acoustic disturbances too high in frequency (ultrasonic) to be heard or too low (infrasonic) to be classed as extensions of those events that can be heard.

A source of sound undergoes rapid changes of shape, size, or position that disturb adjacent elements of the surrounding medium, causing them to move about their equilibrium positions. These disturbances in turn are transmitted elastically to neighboring elements. This chain of events propagates to larger and larger distances, constituting a wave traveling through the medium. If the wave contains the appropriate range of frequencies and impinges on the ear, it generates the nerve impulses that are perceived as hearing.

Acoustic pressure

A sound wave compresses and dilates the material elements it passes through, generating associated pressure fluctuations. An appropriate sensor (a microphone, for example) placed in the sound field will record a time-varying deviation from the equilibrium pressure found at that point within the fluid. The changing total pressure P measured will vary about the equilibrium pressure P₀ by a small amount called the acoustic pressure, p = P - P₀. The SI unit of pressure is the pascal (Pa), equal to 1 newton per square meter (N/m²). Standard atmospheric pressure (14.7 lb/in.²) is approximately 1 bar = 10⁶ dyne/cm² = 10⁵ Pa. For a typical sound in air, the amplitude of the acoustic pressure may be about 0.1 Pa (one-millionth of an atmosphere); most sounds cause relatively slight perturbations of the total pressure. See Pressure, Pressure measurement, Pressure transducer, Sound pressure

Plane waves

One of the more basic sound waves is the traveling plane wave. This is a pressure wave progressing through the medium in one direction, say the +x direction, with infinite extent in the y and z directions. A two-dimensional analog is ocean surf advancing toward a very long, straight, and even beach. See Wave (physics), Wave equation, Wave motion

A most important plane wave, called harmonie, is the smoothly oscillating monofrequency plane wave described by Eq. (1). (1) The amplitude of this wave is P. The phase (argument of the cosine) increases with time, and at a point in space the cosine will pass through one full cycle for each increase in phase of 2&pgr;. The period T required for each cycle must therefore be such that 2&pgr;fT = 2&pgr;, or T = 1/f, so that f = 1/T can be identified as the frequency of oscillation of the pressure wave. During this period T, each portion of the waveform has advanced through a distance λ = cT, and this distance λ must be the wavelength. This gives the fundamental relation (2) (2) between the frequency, wavelength, and speed of sound c in any medium. For example, in air at room temperature the speed of sound is 343 m/s (1125 ft/s). A sound of frequency 1 kHz (1000 cycles per second) will have a wavelength of λ = c/f = 343/1000 m = m (1.1 ft). Lower frequencies will have longer wavelengths: a sound of 100 Hz in air has a wavelength of 3.4 m (11 ft). For comparison, in fresh water at room temperature the speed of sound is 1480 m/s (4856 ft/s), and the wavelength of 1-kHz sound is nearly 1.5 m (5 ft), almost five times greater than the wavelength for the same frequency in air.

Description of sound

The characterization of a sound is based primarily on human psychological responses to it. Because of the nature of human perceptions, the correlations between basically subjective evaluations such as loudness, pitch, and timbre and more physical qualities such as energy, frequency, and frequency spectrum are subtle and not necessarily universal.

The strength of a sound wave is described by its intensity. From basic physical principles, the instantaneous rate at which energy is transmitted by a sound wave through unit area is given by the product of acoustic pressure and the component of particle velocity perpendicular to the area. The time average of this quantity is the acoustic intensity. If all quantities are expressed in SI units (pressure amplitude or effective pressure amplitude in Pa, speed of sound in m/s, and density in kg/m³), then the intensity will be in watts per square meter (W/m²). See Sound intensity

Because of the way the strength of a sound is perceived, it has become conventional to specify the intensity of sound in terms of a logarithmic scale with the (dimensionless) unit of the decibel (dB). An individual with unimpaired hearing has a threshold of perception near 10^-12 W/m² between about 2 and 4 kHz, the frequency range of greatest sensitivity. As the intensity of a sound of fixed frequency is increased, the subjective evaluation of loudness also increases, but not proportionally. Rather, the listener tends to judge that every successive doubling of the acoustic intensity corresponds to the same increase in loudness. For sounds lying higher than 4 kHz or lower than 500 Hz, the sensitivity of the ear is appreciably lessened. Sounds at these frequency extremes must have higher threshold intensity levels before they can be perceived, and doubling of the loudness requires smaller changes in the intensity with the result that at higher levels sounds of equal intensities tend to have more similar loudnesses. It is because of this characteristic that reducing the volume of recorded music causes it to sound thin or tinny, lacking both highs and lows of frequency. Since most sound-measuring equipment detects acoustic pressure rather than intensity, it is convenient to define an equivalent scale in terms of the sound pressure level. The intensity level and sound-pressure level are usually taken as identical, but this is not always true. See Decibel

How “high” sound of a particular frequency appears to be is described by the sense of pitch. A few minutes with a frequency generator and a loudspeaker show that pitch is closely related to the frequency. Higher pitch corresponds to higher frequency, with small influences depending on loudness, duration, and the complexity of the waveform. For the pure tones (monofrequency sounds) encountered mainly in the laboratory, pitch and frequency are not found to be proportional. Doubling the frequency less than doubles the pitch. For the more complex waveforms usually encountered, however, the presence of harmonics favors a proportional relationship between pitch and frequency.

Propagation of sound

Plane waves are a considerable simplification of an actual sound field. The sound radiated from a source (such as a loudspeaker, a hand clap, or a voice) must spread outward much like the widening circles from a pebble thrown into a lake. A simple model of this more realistic case is a spherical source vibrating uniformly in all directions with a single frequency of motion. The sound field must be spherically symmetric with an amplitude that decreases with increasing distance from the source, and the fluid elements must have particle velocities that are directed radially.

Not all sources radiate their sound uniformly in all directions. When someone is speaking in an unconfined space, for example an open field, a listener circling the speaker hears the voice most well defined when the speaker is facing the listener. The voice loses definition when the speaker is facing away from the listener. Higher frequencies tend to be more pronounced in front of the speaker, whereas lower frequencies are perceived more or less uniformly around the speaker.

Diffraction

It is possible to hear but not see around the corner of a tall building. However, higher-frequency sound (with shorter wavelength) tends to bend or “spill” less around edges and corners than does sound of lower frequency. The ability of a wave to spread out after traveling through an opening and to bend around obstacles is termed diffraction. This is why it is often difficult to shield a listener from an undesired source of noise, like blocking aircraft or traffic noise from nearby residences. Simply erecting a brick or concrete wall between source and receiver is often an insufficient remedy, because the sounds may diffract around the top of the wall and reach the listeners with sufficient intensity to be distracting or bothersome. See Acoustic noise, Diffraction

Rays

Since the speed of sound varies with the local temperature (and pressure, in other than perfect gases), the speed of a sound wave can be a function of position. Different portions of a sound wave may travel with different speeds of sound.

Each small element of a surface of constant phase traces a line in space, defining a ray along which acoustic energy travels. The sound beam can then be viewed as a ray bundle, like a sheaf of wheat, with the rays distributed over the cross-sectional area of the surface of constant phase. As the major lobe spreads with distance, this area increases and the rays are less densely concentrated. The number of rays per unit area transverse to the propagation path measures the energy density of the sound at that point.

It is possible to use the concept of rays to study the propagation of a sound field. The ray paths define the trajectories over which acoustic energy is transported by the traveling wave, and the flux density of the rays measures the intensity to be found at each point in space. This approach, an alternative way to study the propagation of sound, is approximate in nature but has the advantage of being very easy to visualize.

Reflection and transmission

If a sound wave traveling in one fluid strikes a boundary between the first fluid and a second, then there may be reflection and transmission of sound. For most cases, it is sufficient to consider the waves to be planar. The first fluid contains the incident wave of intensity I_i and reflected wave of intensity I_r; the second fluid, from which the sound is reflected, contains the transmitted wave of intensity I_t. The directions of the incident, reflected, and transmitted plane sound waves may be specified by the grazing angles Θ_i, Θ_r, and Θ_t (measured between the respective directions of propagation and the plane of the reflecting surface). See Reflection of sound

Absorption

When sound propagates through a medium, there are a number of mechanisms by which the acoustic energy is converted to heat and the sound wave weakened until it is entirely dissipated. This absorption of acoustic energy is characterized by a spatial absorption coefficient for traveling waves. See Sound absorption

Sound

The sensation stimulated in the auditory organs by a vibratory disturbance.

Sound

in the broad sense, the vibratory motion of the particles in anelastic medium, propagating as waves in gaseous, fluid, or solid mediums; in the narrow sense, a phenomenon that is perceived by a special sensory organ in humans and animals. Humans hear sound having a frequency between 16 and 20,000 hertz (Hz). The physical concept of sound includes both audible and inaudible sound. Sound with a frequency below 16 Hz is called infrasound; with a frequency above 20,000 Hz, ultrasound. Very high-frequency elastic waves in the range from 10⁹ to 10¹²–10¹³ Hz are called hyper-sound. The infrasonic frequency region has virtually no lower limit; infrasonic vibrations are encountered in nature at frequencies of tenths and hundredths of a hertz. The frequency range of hypersonic waves is limited at the top by physical factors that characterize the atomic and molecular structure of the medium: the length of an elastic wave must be substantially greater than the free path length of molecules in gases and greater than the interatomic distances in fluids and solids. As a result, hypersound cannot propagate in air at a frequency of 10⁹ Hz or higher or in solids at a frequency higher than 10¹²–10¹³” Hz.

Basic characteristics. An important characteristic of sound is its spectrum, which is produced by expanding the sound into simple harmonic vibrations (so-called frequency sound analysis). The spectrum is continuous if the energy of the sound vibrations is distributed continuously over a fairly broad frequency range; it is a linear spectrum if it has a set of discrete frequency components. Sound having a continuous spectrum is perceived as a noise like the rustling of leaves in the wind or the sounds of mechanisms in operation. A musical sound has a linear spectrum with multiple frequencies; the fundamental frequency determines the pitch of the sound as perceived by hearing, and the set of harmonic components distinguishes its timbre. The spectrum of speech sounds contains formants, which are stable groups of frequency components corresponding to certain phonetic elements. The energy parameter of sound vibrations is the sound intensity—the energy carried by the sound wave through a unit surface, perpendicular to the direction of propagation, per unit time. Sound intensity is a function of the sound pressure amplitude, as well as of the properties of the medium and the shape of the wave. The subjective parameter, which is associated with the intensity of the sound, is loudness, which is dependent on frequency. The human ear is most sensitive in the frequency range from 1 to 5 kHz. In this region the threshold of audibility—that is, the intensity of the weakest audible sounds—is on the order of 10^-12 watts per sq m (W/m²), and the corresponding sound pressure is 10^-5 new-tons per sq m (N/m² ). The upper limit of intensity for sound perception by the human ear is called the threshold of pain; it is slightly dependent on frequency in the audible range and is approximately equal to 1 W/m². Much greater intensities (up to 104 kW/m²) are achieved in ultrasonic technology.

Sound sources. Sound sources are phenomena that produce a local variation in pressure or mechanical stress. Vibrating solid bodies, such as the cones in loudspeakers, the diaphragms in telephones, and the strings and sounding boards in musical instruments, are the most common sound sources; in the ultrasonic frequency range the sources may be plates and rods made from piezoelectric or magnetostrictive materials. Vibrations of limited volumes of the medium itself—for example, in organ pipes, wind instruments, and whistles—may also be sound sources. The vocal apparatus of humans and animals is a complex vibratory system. The vibration of sound sources may be excited by a blow (in the case of a bell) or by plucking (in the case of a string); a self-excited vibration mode can be maintained in such objects by a current of air (in wind instruments). Electroacoustic transducers, in which mechanical vibrations are produced by converting electrical current oscillations of the same frequency, are a broad class of sound sources. In nature, sound is produced when air flows around solid bodies because of the creation and breakaway of vortices (for example, when the wind blows over wires, pipes, and the crests of ocean waves). Low-frequency and infrasonic sounds are produced by explosions and avalanches. The sources of acoustic noise include machines and mechanisms used in technology, as well as gas and water jets. The study of industrial, transportation, and aerodynamic sources of noise is receiving a great deal of attention in view of their harmful effects on the human body and industrial equipment.

Sound receivers. Sound receivers pick up sound energy and convert it into other forms. The hearing apparatus of humans and animals is in this category. In technology, electroacoustic transducers are generally used for the reception of sound: microphones in air, hydrophones in water, and geophones in the earth’s crust. In addition to such transducers, which reproduce the time dependence of the sound signal, there are receivers that measure the parameters of sound waves averaged with respect to time—for example, the Raleigh disk and the acoustic radiometer.

Propagation of sound waves. The propagation of sound waves is characterized primarily by the speed of sound. Longitudinal waves propagate in gaseous and fluid mediums (the direction of the particles’ vibratory motion coincides with the direction of propagation of the wave) at a velocity determined by the compressibility and density of the medium. The speed of sound in dry air at a temperature of 0°C is 330 m/sec, and in fresh water at 17°C it is 1,430 m/sec. In addition to longitudinal waves, transverse waves, for which the direction of the vibrations is perpendicular to the direction of propagation of the wave, as well as surface waves (Rayleigh waves), may propagate in solids. For most metals the velocity of longitudinal waves ranges from 4,000 to 7,000 m/sec; the velocity of transverse waves, between 2,000 and 3,500 m/sec.

During the propagation of waves of great amplitude, the compression phase propagates at a higher velocity than the rarefaction phase, so that the sinusoidal shape of the wave becomes gradually distorted and the sound wave is converted into a shock wave. In many cases sound dispersion is observed, that is, the velocity of propagation is a function of the frequency. Sound dispersion leads to a change in the shape of complex acoustic signals, including a number of harmonic components, and, in particular, to the distortion of sound pulses.

The phenomena of interference and diffraction, which are typical of all types of waves, can occur during the propagation of sound waves. When the size of obstacles and the inhomogeneities of the medium are large compared to the wavelength, the propagation of sound obeys the usual laws of reflection and refraction for waves and may be dealt with from the viewpoint of geometric acoustics.

During the propagation of a sound wave in a given direction, gradual attenuation occurs—that is, its intensity and amplitude decrease. Knowledge of the laws of attenuation is of practical importance in determining the maximum propagation distance for an acoustic signal. Attenuation depends on a number of factors, which become manifest to a greater or lesser degree according to the characteristics of the sound itself (primarily its frequency) and the properties of the medium. All of these factors may be classified in two large groups. The first group includes factors associated with the laws of wave propagation in the medium. Thus, in the case of propagation in an infinite medium, the intensity of a sound from a source of finite size decreases inversely as the square of the distance. Inhomogeneity of the medium’s properties causes scattering of the wave in various directions, thus weakening it in the original direction, as is the case with sound scattered by bubbles in water, by the agitated surface of an ocean, and by atmospheric turbulence; high-frequency ultrasound is scattered in polycrystalline metals and by dislocations in crystals. The propagation of sound in the atmosphere and in the ocean is affected by temperature and pressure distribution and by the force and velocity of the wind. These factors cause bending of the sound rays—that is, refraction—which in particular accounts for the fact that sound is audible farther with the wind than against it. The distribution of the speed of sound with depth in the ocean explains the existence of the so-called underwater sound channel, in which extremely long-range sound propagation is observed: for example, the sound of an explosion propagates for more than 5,000 km.

The second group of factors determining sound attenuation is associated with the physical processes in a substance, including the irreversible transformation of sound energy into other forms, mainly heat—that is, the absorption of sound, which is caused by the viscosity and thermal conductivity of the medium (“classical absorption”)—and the transformation of sound energy into the energy of intramolecular processes (molecular or relaxation absorption). Sound absorption increases markedly with frequency. Therefore, high-frequency ultrasound and hypersound usually propagate only over very short distances, most often no more than several centimeters. Infrasonic waves, which are distinguished by low absorption and weak scattering, are propagated the farthest in the atmosphere, in water, and in the earth’s crust. At high ultrasonic and hypersonic frequencies additional absorption occurs in solids as a result of the interaction of the waves with the thermal vibrations of the crystal lattice, with electrons, and with light waves. Under certain conditions this interaction can produce “negative absorption,” or the amplification of sound waves.

The importance of sound waves, and consequently their study (in acoustics), is extremely great. Since ancient times, sound has served as a means of communication and signaling. The study of all of its characteristics has made possible the development of more advanced data transmission systems, an increase in the range of signaling systems, and the creation of improved musical instruments. Sound waves are virtually the only form of signals that propagate in water, where they are used for submarine communications, navigation, and echolocation. Low-frequency sound is a tool for the study of the earth’s crust. The practical application of ultrasound has created ultrasonics, an entire branch of modern technology. Ultrasound is used for monitoring and measurement (particularly in flaw detection), as well as for operations on substances (ultrasonic cleaning, mechanical treatment, and welding). High-frequency sound waves, particularly hypersound, are an important means for research in solid-state physics.

REFERENCES

Strutt, J. (Lord Rayleigh). Teoriia zvuka, 2nd ed., vols. 1–2. Moscow, 1955. (Translated from English.)
Krasil’ nikov, V. A.Zvukovye i ultrazvukovye volny v vozdukhe, vode i tverdykh telakh, 3rd ed. Moscow, 1960.
Rozenberg, L. D. Rasskaz O neslyshimom zvuke. Moscow, 1961.

I. P. GOLIAMINA

sound

[sau̇nd] (acoustics) An alteration of properties of an elastic medium, such as pressure, particle displacement, or density, that propagates through the medium, or a superposition of such alterations; sound waves having frequencies above the audible (sonic) range are termed ultrasonic waves; those with frequencies below the sonic range are called infrasonic waves. Also known as acoustic wave; sound wave. (physiology) The auditory sensation which is produced by these alterations. Also known as sound sensation.

sound

An oscillation in pressure of the atmosphere which is capable of being detected by the human ear.

sound

¹1. a. a periodic disturbance in the pressure or density of a fluid or in the elastic strain of a solid, produced by a vibrating object. It has a velocity in air at sea level at 0°C of 331 metres per second (741 miles per hour) and travels as longitudinal waves b. (as modifier): a sound wave 2. the sensation produced by such a periodic disturbance in the organs of hearing 3. Slang music, esp rock, jazz, or pop

sound

²1. Law (of a title, etc.) free from defect; legally valid 2. Logica. (of a deductive argument) valid b. (of an inductive argument) according with whatever principles ensure the high probability of the truth of the conclusion given the truth of the premises c. another word for consistent

sound

¹ Med an instrument for insertion into a bodily cavity or passage to dilate strictures, dislodge foreign material, etc.

sound

²1. a relatively narrow channel between two larger areas of sea or between an island and the mainland 2. an inlet or deep bay of the sea 3. the air bladder of a fish

Sound

the. a strait between SW Sweden and Zealand (Denmark), linking the Kattegat with the Baltic: busy shipping lane; spanned by a bridge in 2000. Length: 113 km (70 miles). Narrowest point: 5 km (3 miles)

sound

(1)audio.

sound

(logic)An inference system A is sound with respect toanother system B if A can only reach conclusions which aretrue in B. A type inference system is considered sound withrespect to a semantics if the type inferred for anexpression is the same as the type inferred for the meaning ofthat expression under the semantics.

The dual to soundness is completeness.

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Generation of Sound Waves

Characteristics of Sound Waves

Characteristics of Musical Sounds

Bibliography

Sound

Acoustic pressure

Plane waves

Description of sound

Propagation of sound

Diffraction

Rays

Reflection and transmission

Absorption

Sound

Sound

REFERENCES

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Synonyms for sound

noun noise

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noun idea

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noun cry

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noun tone

sound¹

sound²

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sound²

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