| Popis: |
Reverberation chambers used for acoustical measurements should have completely random sound fields. We denote by R the cross‐correlation coefficient for the sound pressures at two points a distance r apart. R = 〈p1p2〉Av/(〈p12〉Av〈p22〉Av)12, where p1 is the sound pressure at one point, p2 that at the other, and the angular brackets denote long time averages. In a random sound field, R = (sinkr)/kr, where k = 2π/(the wavelength of the sound). An instrument for measuring and recording R as a function of time is described. A feature of this instrument is the use of a recorder's servomechanism to measure the ratio of two dc voltages. The results of correlation measurements in reverberant sound fields are given. |
