Counting reflections in measured acoustic impulse response functions.

Abstract

A novel method of counting reflections and reflection density has been developed. The method is borrowed from non‐linear studies of fractal systems where time delayed versions of a signal are plotted against each other. In this case, the sound pressure p(t) of an impulse response function is plotted against its time derivative, dp(t)/dt. Each resulting circle represents a reflection. The results are, in effect, a dynamic version of (a normally steady state) Lissajous figure. Measured reflection counts are much lower than would be expected from theoretical predictions, primarily in the hundreds rather than thousands. A new method for estimating the temporal border between discrete and diffuse reflections is also presented.