Two‐ear correlation in the statistical sound fields of rooms

The normalized correlation function R( f ) connecting the signals at the left and right ears was measured in a reverberant room as a function of frequency. Head diffraction effects are made evident by comparing these data to the correlation function predicted and observed for two microphones separated by a headwidth (15 cm) of space and moving in the same room. In contrast to the familiar two‐mike sinc(δ) correlation (δ=kd), head diffraction gives a two‐ear correlation function which is well described by sinc(αδ)/[1+(βδ)4]1/2, where α=2.2 and β=0.5. The dominant effect of head diffraction is to lower  fD, the decoupling frequency [first zero of R( f )] to 500 Hz, about half the no‐head value. The denominator in the fitted correlation function represents the near total independence of the signals at the two ears above  fD. Thus with head diffraction the variance in a paired‐mike room averaged pressure amplitude estimate at around 500 Hz is already as small as that obtained sans head only at frequencies abo...