Method and apparatus for processing signals of a spherical microphone array on a rigid sphere used for generating an ambisonics representation of the sound field

A microphone array, microphone technology, applied in the direction of the spatial/structural arrangement of microphones, stereo systems, microphone signal combinations, etc.

Active Publication Date: 2014-09-10
DOLBY INT AB
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

Such an Ambisonics representation describes the sound field but includes the effects of the microphone array

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  • Method and apparatus for processing signals of a spherical microphone array on a rigid sphere used for generating an ambisonics representation of the sound field
  • Method and apparatus for processing signals of a spherical microphone array on a rigid sphere used for generating an ambisonics representation of the sound field
  • Method and apparatus for processing signals of a spherical microphone array on a rigid sphere used for generating an ambisonics representation of the sound field

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Embodiment Construction

[0038] Spherical Microphone Array Processing - Ambisonics Theory

[0039] Ambisonics decoding is defined by assuming loudspeakers that are radiating a sound field of plane waves. See M.A. Poletti, "Three-Dimensional Surround SoundSystems Based on Spherical Harmonic" (Journal of the Audio Engineering Society, 2005, Vol. 53, No. 11, pp. 1004-1025):

[0040] w ( Ω l , k ) = Σ n = 0 N Σ m = - n n D n m ( Ω l ) d n m ( k ) - - ...

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Abstract

Spherical microphone arrays capture a three-dimensional sound field ( P ( © c , t )) for generating an Ambisonics representation A n m t , where the pressure distribution on the surface of the sphere is sampled by the capsules of the array. The impact of the microphones on the captured sound field is removed using the inverse microphone transfer function. The equalisation of the transfer function of the microphone array is a big problem because the reciprocal of the transfer function causes high gains for small values in the transfer function and these small values are affected by transducer noise. The invention estimates (73) the signal-to-noise ratio between the average sound field power and the noise power from the microphone array capsules, computes (74) the average spatial signal power at the point of origin for a diffuse sound field, and designs in the frequency domain the frequency response of the equalisation filter from the square root of the fraction of a given reference power and the simulated power at the point of origin.

Description

technical field [0001] The present invention relates to a method and apparatus for processing signals of a spherical microphone array on a rigid sphere for producing an Ambisonics representation of a sound field, wherein an equalization filter is applied to the inverse microphone array response. Background technique [0002] A spherical microphone array provides the ability to capture a three-dimensional sound field. One method of storing and manipulating sound fields is the Ambisonics representation. Ambisonics uses orthogonal spherical functions to describe the sound field in a region around the origin (also known as the sweet spot). The precision of this description is determined by the order N of Ambisonics, where a finite number of Ambisonics coefficients describe the sound field. The maximum Ambisonics order of a spherical array is limited by the number of microphone capsules, which must be equal to or greater than the number of Ambisonics coefficients o=(N+1) 2 . ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04R3/00H04R5/027
CPCH04R5/027H04S2400/15H04R3/005H04R1/326H04R1/406H04R29/005H04R2201/401
Inventor S.科顿J-M.贝特克A.克鲁格
Owner DOLBY INT AB
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