Research On Speaker Array Sound Field Shape Control Methods

Nowadays science and technology are developing rapidly,people are pursuing sound of high quality.Places like theater require clear sound,communication by phone emphasizes security,privacy is important when playing music,square dance needs to avoid disturbing others,solutions to these problems are closely related to speaker array sound field shape control.This thesis aims at studying sound field shape control methods,including directivity control,constant beam width control and beam deflection around speaker array,to realize directional transmission of sound,keep stability of sound field coverage and produce 3D sound effect separately.Based on directivity function of circular array element,effects of element radius and sound frequency on sound field shape are analyzed.The influences of directional plane,sound frequency,array element geometric parameters and array element material parameters on sound field shape of rectangular array element are discussed on the basis of its directivity function.After that,geometric and material parameters of rectangular array element are determined on requirement of different equipment for sound field shape.Sound field shape control methods are studied on linear array and planar array composed of point array element via array signal processing theory.For uniform linear array,effects of number of array elements,array element distance,sound frequency and amplitude weighting methods on sound field directivity are considered.Single octave and multi-octave constant beam width are realized by combining high frequency subarray and low frequency subarray.The beam deflection is obtained through adjusting phases of array elements.About uniform planar array,chebyshev weighting and taylor weighting are used to improve effectively directivity of array sound field,constant beamwidth control is implemented by combined high frequency subarray and low frequency subarray and the beam deflection in both elevation and azimuth directions is realized at the same time.In terms of sound field shape control of rectangular array element planar array,its corresponding array directivity function is deduced.After that,chebyshev weighting and taylor weighting are applied to improve directivity of array sound field.Single octave and multi-octave constant beam width combined array are designed to ensure stability of sound field coverage.For beam deflection of rectangular array element planar array,it is realized in both elevation and azimuth directions at the same time.Referring to speaker array sound field shape control experiment,experiment platform is designed and built up.Limited by experiment conditions,this thesis just uses horn speakers(circular array elements)to establish linear and planar array.Effects of directivity control through amplitude weighting,constant beam width control through combining high frequency subarray and low frequency subarray and beam deflection are tested.Experimental results indicate the effectiveness of sound field shape control methods.