This paper presents a method of localizing sound sources in 3-D space by the use of an array of microphones. In order to obtain a device with uniform characteristics in all directions the positions of the microphones are restricted to a spherical surface. The restriction to a spherical geometry also facilitates an expansion of the sound field impinging on the sphere into spherical harmonics and functions describing the radial dependence of the sound field. The coefficients of the spherical harmonics contain the information of the direction to the sound source. In order to obtain the expansion coefficients needed, the sound pressure must be integrated over the spherical surface. The limited number of microphones poses a limit to the degree of spherical harmonic that can be extracted, and thereby to the angular resolution of the device. It also transforms the surface integral of the sound pressure into a problem of numerical integration. The paper addresses the problem of finding the optimum number and positions of the microphones (integration points). Finally measurements are carried out using a prototype of the array in an anechoic chamber.
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