Experimental methods for determining the cross-over frequency above which phaseless geometrical methods for room acoustics computer simulation is suitable

Abstract

The most used computer codes for simulating the sound propagation in closed spaces are based on geometrical acoustics. Such an approach is known to be suitable when sound waves interference does not play a major role. For estimating a cross-over frequency above which this condition is met, acousticians use a simple formula for the so called “Schroeder frequency,” which in turn is related to modal overlap. In this work, two methods for observing experimentally the cross-over frequency above which wave interference may be disconsidered are presented. One of them is related to the statistical independence of room impulse responses (in space), while the other one is based on the analysis of impulse responses' phase information within a frequency band. Preliminary results for a shoebox room, based on analytically generated impulse responses, and measurements performed in an auditorium are shown, and indicate similar frequency values, also comparable to the estimated Schroeder frequencies.