Study On The Radiation Characteristics Of Loudspeaker Arrays

A loudspeaker array is a sound source which is composed of several loudspeakers.Compared with a single loudspeaker,a loudspeaker array has more flexible directional characteristics and higher acoustic output power.So loudspeaker arrays are widely used in the audio industry and become research highlights.In this dissertation,the radiation characteristics of loudspeaker arrays,especially the sound field characteristics and directional characteristics,are analyzed and optimized.First,a loudspeaker array can be analyzed using Multi-Point Source Model(MPSM)and Line Source Model(LSM).In this dissertation,several classic loudspeaker arrays are analyzed using these two models,including their sound field characteristics and directional characteristics.Second,the straight-line MPSM loudspeaker array is analyzed and optimized,and the optimization methods of omnidirectional array are proposed.Based on the Discrete-time Fourier Transform relationship between the directivity and frequency-independent array weights,several optimization methods have been proposed,including all-pass Infinite-Impulse-Response filter method,Inverse Discrete-time Fourier Transform method,special-function method and optimal array-weight method.Two optimized omnidirectional arrays are also proposed.Theoretical and experimental results indicate that these two arrays can both radiate higher acoustic power than classic arrays and have broadband frequency-independent omnidirectivity.Third,the curved-line MPSM loudspeaker array is analyzed and optimized,and the circularly-curved Multi-CBT array and straight-line delay-curved Multi-CBT array are proposed by using overlapped Legendre shadings based on CBT theory.The sound fields and directivities of several Multi-CBT arrays are analyzed under application-oriented scenarios.Simulation results indicate that Multi-CBT arrays have customizable frequency-independent directivities in broadband.The results also show that among elliptically-curved and circularly-curved arrays,only the circularly-curved arrays can achieve frequency-independent directivity.Fourth,a fast and accurate measuring method of waveguide used in loudspeaker array is proposed.The whole radiated sound field of waveguide can be accurately measured by using small experimental installations.This method fill the blank in the field of the loudspeaker-array waveguide measurement.The experimental results indicate that the average error of the proposed method is less than ±1 dB.Then,several evaluation indicators of acoustic waveguide are proposed,including equivalent length and active radiation factor of waveguide.The methods for achieving these indicators are also proposed,including certain-angle method and directivity-fitting method.Finally,the waveguide used in loudspeaker array is optimized and a new kind of acoustic waveguide is also proposed.Theoretical and experimental results indicate that the active radiation factor of the new waveguides is larger than 98%,which is better than existing acoustic waveguides.The new waveguide can improve the performance of loudspeaker array a lot.