Analytical approach to transforming filter design for sound field recording and reproduction using circular arrays with a spherical baffle

Abstract

A sound field recording and reproduction method using circular arrays of microphones and loudspeakers with a spherical baffle is proposed. The spherical baffle is an acoustically rigid object on which the microphone array is mounted. The driving signals of the loudspeakers must be obtained from the signals received by the microphones. A transform filter for this signal conversion is analytically derived, which is referred to as the wave field reconstruction filter. The proposed method using a spherical baffle is compared with methods using an array of directional microphones and a microphone array mounted on a cylindrical baffle. Numerical simulations indicated that the proposed method is advantageous for sound field recording and reproduction compared with the other two methods. The results of measurement experiments in a real environment are also demonstrated.

Optimizing Source and Sensor Placement for Sound Field Control: An Overview

“…Uniqueness can be obtained by using multiple layers, with measurements inside the sphere where the eigenmodes have nonzero values, or with directional microphones, making the forbidden eigenfrequencies complex [12], [54]. Alternatively, microphone arrays mounted on an acoustically rigid object also prevent this nonuniqueness issue [10], [13], [15], [55], [56]. Such recording and reproduction methods based on spatial Fourier analysis of the sound field can only be applied for simple array geometries [11], [14], [46], [47], [57], where the regular sampling of the array geometry is usually applied.…”

“…The positions of the loudspeakers for reproduction and microphones for recording are generally determined by regularly discretizing the continuous surface of the array. The forbidden frequency problem is typically avoided by using microphones mounted on an acoustically rigid object, directional microphones, or multiple layers of microphone arrays [10], [12]- [15]. This regular placement performs well in a free field and when the array has a simple shape, such as a sphere, plane, circle, or line.…”

The Far-Field Equatorial Array for Binaural Rendering

“…SH decomposition based on a circular array on a planar scatterer was presented in [17] and based on concentric circular arrays without a scatterer in [18]. [19] used an equatorial microphone array for resynthesis of the sound field using a circular loudspeaker array using a formulation that was partially in SH.…”

Microphone array beamforming based on maximization of the front-to-back ratio

“…Beamforming with microphone arrays has attracted much attention recently due to its wide range of applications, such as hands-free voice communications and human-machine interfaces (Brandstein and Ward, 2001;Benesty et al, 2008;Benesty et al, 2017). Many beamforming algorithms were developed in the literature such as the delay-and-sum (DS) beamformer (Schelkunoff, 1943), broadband beamformers based narrowband decomposition (Doclo and Moonen, 2003;Benesty et al, 2007;Capon, 1969;Frost, 1972) and nested arrays (Zheng et al, 2004;Kellermann, 1991;Elko and Meyer, 2008), modal beamformers (Torres et al, 2012;Yan et al, 2011;Koyama et al, 2016;Park and Rafaely, 2005), superdirective beamformers (Cox et al, 1986;Kates, 1993;Wang et al, 2014), and differential beamformers with differential microphone arrays (DMAs) (Elko, 2000;Elko and Meyer, 2008;Chen et al, 2014;Pan et al, 2015b;Abhayapala and Gupta, 2010;Weinberger et al, 1933;Olson, 1946;Sessler and West, 1971;Warren and Thompson, 2006). Among these, differential beamformers are now widely used in a wide spectrum of small devices such as smart speakers, smartphones, and robotics, primarily because they exhibit frequency-invariant beampatterns and can achieve high directivity factors (DFs) with small apertures.…”