Study of nonuniform linear differential microphone arrays with the minimum-norm filter

ICASSP 2021 - 2021 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)

Bertuletti

et al. 2021

The literature is rich with techniques for the design of small-size Differential Microphone Arrays (DMAs), known for their almost frequency-invariant beampatterns and low computational cost. Few works, instead, discuss the properties of beamformers based on multiple DMA units. In this paper, we consider arbitrarily shaped planar arrays of DMA units. In turn, each DMA unit is a first-order continuously-steerable differential microphone characterized by an arbitrary configuration of omnidirectional sensors and a symmetric beampattern. We present a beamforming technique that, assumed all the DMA units to steer identical beams in the same direction, allows us to approach the behavior of a Delay-And-Sum beamformer or Super-Directive beamformer by solely varying a single scalar parameter. Efficient implementations of the proposed beamformers can be developed by taking into account that, for a wide range of frequencies, the values of such a parameter are practically invariant with respect to the geometry of the array.

Section: Introductionmentioning

confidence: 99%

Arrays of First-Order Steerable Differential Microphones

ICASSP 2021 - 2021 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)

Bertuletti

et al. 2021

“…Moreover, they suffer from the well-known problem of front-back ambiguity, which often limits their applicability in practical scenarios. Nonuniform linear DMAs have also been proposed in [31], showing that they can significantly improve the robustness against white noise with respect to uniform linear DMAs, especially at low frequencies. Uniform circular DMAs, on the other hand, exhibit much better steering capabilities.…”

Section: Introductionmentioning

confidence: 99%

Efficient Implementations of First-Order Steerable Differential Microphone Arrays With Arbitrary Planar Geometry

IEEE/ACM Trans. Audio Speech Lang. Process.

Antonacci

et al. 2020

We present a spatial filtering approach to firstorder steerable Differential Microphone Arrays (DMAs) with arbitrary planar geometry. In particular, the design of the spatial filter is based on a recently proposed frequency-domain design methodology that approximates, in a least-square sense, a target beampattern using the Jacobi-Anger expansion involving Bessel functions. Despite the generality of that approach, however, its computational cost turns out to be excessive when working with limited processing resources. The beamforming technique proposed in this manuscript overcomes this issue by exploiting the fact that in DMAs the spacing between sensors is typically smaller than the smallest wavelength of audio signals of interest. This allows us to substitute zero-and first-order Bessel functions with their Taylor series approximation truncated to the first order. Moreover, we show that this approximation allows us to derive an efficient discrete-time-domain implementation of firstorder steerable differential beamformers based on arrays with arbitrary geometries.

“…Despite the highlighted features, DMs suffer from some problems that have been deeply investigated in the literature. In particular, they have been shown to amplify white noise, especially at low frequency [4]- [6], [10] and to exhibit high sensitivity to sensor mismatches [3], [22], [23]. The relevance of these problems grows as the order N increases, which explains why most of the literature focuses on first-or secondorder DMs.…”

Section: Introductionmentioning

confidence: 99%

Uniform Linear Arrays of First-Order Steerable Differential Microphones

IEEE/ACM Trans. Audio Speech Lang. Process.

Antonacci

et al. 2019

We propose a spatial filtering method for linear arrays of First-Order Steerable Differential Microphones (FOS-DMs), which operates in two layers. In the former, signals acquired by individual microphones are locally filtered to produce the outputs of the FOSDMs. In the latter, the outputs of the FOS-DMs are processed by another filter. We analyse different design methodologies and study the conditions under which the two filtering layers can be decoupled. The proposed two-layer spatial filter can be flexibly controlled with a single scalar parameter, which can be chosen, for example, to maximize the White Noise Gain (like in a Delay-and-Sum beamformer); or to maximize the Directivity Factor (like in a Super-Directive beamformer); without needing any matrix inversion. The effectiveness of the proposed beamforming method is compared with traditional spatial filtering techniques using different metrics.