Impulse‐response and transfer‐function measurements in rooms by m sequence cross correlation

Abstract

The impulse response and transfer function between a sound source and receiver in a room can be measured using cross‐correlation techniques with a maximum‐length sequence as the signal source. A graphic representation of time evolution of direct sound, echoes, scattering, etc. (via the impulse response) and of spectral effects (via the transfer function) provide tools for acoustical design. The methods are illustrated for diffraction around an edge in an anechoic chamber. “Textbook”‐like interference patterns are not seen because of the broadband nature of the signal. Instead, a quantitative measure of scattering, appropriate for speech and music, is obtained. Quantitative spectral measures are obtained using the transfer function. In an ordinary room, the effects of changing reflecting, scattering, and absorbing walls and objects and of displacing source and receiver are graphically displayed. The effects of modifying and adjusting sound‐reinforcement systems are quantified. The impulse response, and com...