Directivity of Acoustic Transmitters and Receivers

the ability to transmit (or receive) sound waves more strongly in some directions than in others. For the case of transmission, the directivity is determined by the interference of coherent sound vibrations that arrive at some point of the medium from individual sections of the transmitter that are small in comparison with the wavelength in the medium. For the case of reception, directivity is caused by the interference of pressures on the surface of the receiver.

Figure 1. Typical form of directivity characteristics of acoustic transmitter

The directivity of acoustic transmitters and receivers is usually described by (1) the directivity characteristics, the ratio of the sound pressure in particular directions to the sound pressure in the direction of maximum radiation, represented as a function of direction, and (2) the directivity factor K, which is the ratio of the intensity of the radiation generated by a given transmitter in the direction of maximum radiation to the intensity of a nondirectional transmitter that has the same power and is at the same distance. Directivity characteristics are usually represented in a polar diagram for some section of a plane passing through the direction of maximum radiation (see Figure 1).