Abstract
The direction-of-arrival (DoA) estimation from spherical microphone array data requires mode strength compensation for removing the dependency on the array surface impedance. However, in practice, mismatches exist in the actual and modeled surface impedances and degrade the DoA estimation performance. Herein, a non-parametric beamformer that can accurately estimate DoAs under the mode strength mismatch is proposed. The technique utilizes a block-diagonal covariance matrix and order-dependent normalization of spherical harmonic coefficients. The proposed method tested for various surface impedance mismatches and DoAs shows robust estimation performance with reduced dependency on the array surface impedance.
Highlights
Spherical microphone arrays (SMAs) have been used extensively to estimate the direction-of-arrival (DoA) of sound sources.1–3 The SMA is advantageous as it allows for omnidirectional DoA estimation with rotational symmetry
A block-diagonal processing technique for robust DoA estimation against surface impedance mismatch from the theoretical model was proposed
Dependency on the array surface impedance was compensated by omitting the off diagonal blocks of the covariance matrix and normalizing the diagonal blocks using the measured spherical harmonic coefficients (SHCs) of the same order. These two modifications remove the inter-order dependency related to the mode strength, thereby reducing the effect of the surface impedance
Summary
Spherical microphone arrays (SMAs) have been used extensively to estimate the direction-of-arrival (DoA) of sound sources. The SMA is advantageous as it allows for omnidirectional DoA estimation with rotational symmetry. SHCs obtained via SFT naturally include the mode strength for the frequency, radius, and surface impedance of an array. Any mismatch to the actual surface impedance or corresponding mode strength can significantly degrade the performance of DoA estimation. The DI changed considerably for various surface materials This shows that DoA estimation can be affected significantly by the acoustic surface impedance or mode strength of the microphone array. The main objective of this study is to reduce the effect of mode strength mismatch on beamforming. This problem can be mitigated using the parametric DoA estimation technique (EB-ESPRIT), which identifies DoAs based on the recurrence relations between SHCs of the same order. Asa.scitation.org/journal/jel information between SHCs of the same order and discuss the possible advantages and disadvantages when applied to various data with different signal-to-noise ratios (SNRs) and surface impedance mismatches
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