Application of cepstral techniques to ground‐reflection effects in measured acoustic spectra

Abstract

In acoustic measurements such as those conducted outdoors for static jet‐engine noise research, aircraft‐flyover noise certification, and motor‐vehicle regulation, ground reflections create multipath conditions characterized by different signal arrival times which cause signal reinforcements and cancellations at the microphone. This generates undesirable effects on the measured spectra. Cepstral techniques, developed in speech processing to identify echo delay times, have been applied to the ground‐reflection problem. Results indicate that cepstral techniques can produce a spectrum due to intensity addition only of the direct and reflected signals.