Abstract
Specific beampatterns of spherical microphone arrays (SMAs) are designed for different noise scenarios. The standard beampattern usually achieves optimum value in one of the performance indicators. Additionally, in acoustics scenarios where positions of several noise sources are known, the beampattern for SMA should be designed to reject signals from noise orientations. This paper presents a flexible beamformer design method for SMA. The beampattern expression is transformed from spherical harmonics expansion to the common polynomial expression, which facilitates the implementation of the standard beampattern and the novel pattern where the zero positions are assigned to reject multiple noise sources. Simulation results reveal that the proposed beamformer shows better flexibility over the high directivity beamformer and Dolph-Chebychev beamformer. The deep-null problem existing in the open-sphere SMA is also discussed and can be mitigated by reducing the radius or increasing the order of the beamformer.
Highlights
By exploiting the spatial diversity information in the sound field, the microphone arrays (MAs) are capable of enhancing the speech signal contaminated by noise, reverberation and interference [1]–[3]
The performance of the MA is affected by various factors like signal spectral range, acoustic surrounding, applied algorithm, element quantity and geometry
Since the beampattern of the linear MA (LMA) is dependent on the steering direction, the poor steering flexibility becomes a big drawback of the LMA
Summary
By exploiting the spatial diversity information in the sound field, the microphone arrays (MAs) are capable of enhancing the speech signal contaminated by noise, reverberation and interference [1]–[3]. To obtain the desired beampattern, the processing algorithm is formulated in the spherical harmonics domain, where the coefficients of the beamformer filter are computed from a constrained optimization problem. BEAMFORMING FOR SMA Generally, in an open sphere, the unit-amplitude plane wave that comes from the direction (θ,ψ) can be decomposed in the spherical harmonic domain [3]. The zero of bn lead to an infinite value of the filter coefficient hN (ω), which further cause significant SNR gain (WNG and DF defined in (12) and (15) respectively) degradation at some frequency bands [3], [19], [21]. The value of bn approaches zero except b0, and higher order n corresponds to smaller bn, which causes white noise amplification, especially in the cases of high-order beamformer and small aperture array. The open-sphere SMA with omnidirectional elements is considered
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
