Power Response and Modal Decay Estimation of Room Reflections from Spherical Microphone Array Measurements Using Eigenbeam Spatial Correlation Model

Amy Bastine,Jihui (Aimee) Zhang,Thushara D Abhayapala

doi:10.3390/app11167688

Abstract

Modal decays and modal power distribution in acoustic environments are key factors in deciding the perceptual quality and performance accuracy of audio applications. This paper presents the application of the eigenbeam spatial correlation method in estimating the time-frequency-dependent directional reflection powers and modal decay times. The experimental results evaluate the application of the proposed technique for two rooms with distinct environments using their room impulse response (RIR) measurements recorded by a spherical microphone array. The paper discusses the classical concepts behind room mode distribution and the reasons behind their complex behavior in real environments. The time-frequency spectrum of room reflections, the dominant reflection locations, and the directional decay rates emulate a realistic response with respect to the theoretical expectations. The experimental observations prove that our model is a promising tool in characterizing early and late reflections, which will be beneficial in controlling the perceptual factors of room acoustics.

Highlights

In any enclosed acoustic space, the sound received by a listener is the superposition of the direct sound from the source and the reflected sounds from the surrounding surfaces
We presented a reflection power response estimation technique utilizing the spatial correlation of higher-order eigenbeams derived from spherical microphone array measurements
The formulation of the reflection gain as a function of time, frequency, and direction helps in comprehending a faithful room response for a realistic non-diffuse sound field

Summary

Introduction

In any enclosed acoustic space, the sound received by a listener is the superposition of the direct sound from the source and the reflected sounds from the surrounding surfaces. The numerous reflections termed reverberation cause persistence of sound even after the source ceases, until these reflected waves decay due to absorption by the surrounding surfaces. The intricate sound field generated by these reflected waves provides the sense of acoustic space to the perceived sound. The study of reverberation is complicated since it is a product of many factors like sound frequency, room shape, room size, room geometry, source and receiver locations, source and receiver directivity, etc. A comprehensive understanding of the reflection sound field distribution, resonant frequencies, and modal decay rates is necessary to control audible artifacts and achieve desired sound perception quality in room acoustic applications

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