Two-ear correlation in the statistical sound fields of rooms
Ian M. Lindevald, A. H. Benade · The Journal of the Acoustical Society of America · 1986
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 above 1200 Hz.