| 释义 |
low ˈfrequency
[f. low a. + frequency 4.]
1. a. A frequency (see frequency 4 b) having a relatively small number of cycles in a second; applied esp. to an electric current or voltage, an electromagnetic wave, or a sound wave. Abbrev. L.F., esp. in radio and telecommunications, where it also refers specifically to electromagnetic waves of 30–300 kilohertz.
1900M. A. Oudin Stand. Polyphase Apparatus xiv. 242 Transmissions of power are accomplished at a comparatively low frequency. 1928Daily Mail 25 July 18/1 The best Gramophone and Wireless Sets at present in use fail to reproduce the low-frequency of bass notes in anything like proper proportion. 1933B.B.C. Year-Bk. 384 Actually the microphone responds from very low frequencies up to about 8000 cycles per second. 1934[see high frequency 1 a]. 1943C. L. Boltz Basic Radio vii. 121 In considering an imaginary capacitance, that of a tumbler switch,..we judged its capacitance in thousandths of a µµF. At low frequencies the reactance of such a switch is in perhaps millions of megohms. 1960H. Carter Dict. Electronics 169 Low frequency. (1) A relative term used to distinguish waves or oscillations of a particular frequency or band of frequencies from those of higher frequencies. (2) More specifically applied to radio waves of frequencies between 30 and 300 kc/s, corresponding to the long wave range. (3) The term is also loosely applied to the audio-frequency signals in a radio receiver to distinguish them from the ‘high frequency’, i.e. the radio- and intermediate-frequency signals. 1962A. Nisbett Technique Sound Studio iv. 78 The second harmonic [of the mains frequency] is generally the most serious component [of hum] except in certain types of hi-fi loudspeaker cabinet which provide a high output at low frequencies.
b. A low rate of occurrence, in space or time.
1935[see high frequency 1 b].
2. attrib. (usu. with hyphen).
a. In sense 1 a.
1900Engineering 28 Sept. 412/3 Low frequency induction telegraphy experiments..were not considered in this report. 1920H. M. Dowsett Wireless Telegr. v. 118 Low-frequency amplification is the process applied to the signal current after its form has been altered by rectification so that it can affect a telephone. 1923Radio Times 28 Sept. 36 Its volume is limited only by the amount of low frequency amplification employed in the receiving set. 1926J. S. Huxley Ess. Pop. Sci. xvii. 191 The special sense-organs for perceiving low-frequency vibrations in water which, like a herring or any other fish, it [sc. the tadpole] carries on a ‘lateral line’ along its flank. 1934B.B.C. Year-Bk. 385 The output from the microphone is taken to a two-stage low-frequency amplifier. 1941Electronic Engin. XIV. 404 Low frequency response is expressed in the form of a curve showing variation in power output at different frequencies. 1964W. Jassem in D. Abercrombie et al. Daniel Jones 344 The level of this low-frequency noise in the spectrum is 20–25 db below the peak at the higher frequencies. 1973Boyd & Parkes Dark Number viii. 83 Some stimuli are so reverberant they just hum on as a low-frequency signal programmed into your unconscious.
b. In sense 1 b: occurring rarely, involving relatively few instances.
1957Publ. Amer. Dial. Soc. xxviii. 78 Low-frequency verbs like asseverate, reiterate, aver, etc.,..would rarely be initials without that, or parentheticals. 1963Ervin & Miller in J. A. Fishman Readings Sociol. of Lang. (1968) 79 The evidence..reveals a high degree of similarity in the existence of such sequences of high-frequency and low-frequency items. 1971Brit. Med. Bull. XXVII. 19/1 Much of the risk to people from tribes where the frequency [of cancer of the penis] is high is lost when they move to low-frequency areas. |