Gary W. Elko
Acoust. Res. Dept., AT&T Bell Labs., Murray Hill, NJ 07974
The directivity index is a considerably useful measure in quantifying the directional properties of electroacoustic transducers. For microphones used in reverberant environments, the directivity index gives a rough estimate of the gain in signal-to-noise ratio. The measurement of the directivity index of a transducer is complicated by the need to measure over a spherical surface that is in the far field of the transducer. This talk will present a new method for measuring the directivity index in a diffuse reverberant environment. The method uses the frequency response spectral variance to estimate the distance from a point source to a point receiver in a reverberant field. If the source-to-receiver distance, reverberation time, room surface area, and volume are known, the directivity factor can be calculated explicitly from the spectra variance. The method and its limitations will be discussed in the talk.