A Comparative Performance Research On The Typical Method Of The Microphone Array Near-field Beamforming

Beamforming is one of the core technologies in microphone array signal processing,which continues and develops the method of array signal processing technology.Most researches on traditional beamforming methods focus on far field narrowband signal processing which is suitable for the situation that the target signal is in the far field of array range.When the microphone array system is applied to the near field environment such as small conference rooms and car hands-free phones,using far field signal processing model will be obviously ineffective.In addition,the target signals come from broadband signal like voice in the near field applications of microphone array system.Therefore,the research on beamforming method of narrowband and broadband microphone of array near-field is more in line with the practical applications of microphone array system.The method of the near-field microphone array beamforming study in this paper is mainly based on spherical wave model.First of all,after studying the near field signal processing model,we can get the near field array response matrix according to near field signal propagation model,thus get the uniform line array near field oriented vector as well.Compared with the far-field array response matrix,near field array response matrix changes according to the azimuth and distance,while the far-field array response matrix is only affected by the change of azimuth.Secondly,after studying the near-field narrowband beamforming methods which mainly includes conventional beam forming,minimum variance distortionless response(MVDR)beamforming,least mean square(LMS)algorithm,recursive least mean square(RLS)algorithm and sample matrix inversion(SMI)algorithm.Making simulation experiment on this several kinds of narrowband beamforming method based on near field uniform linear array,we can compare their performance of resolution ability,anti-interference ability,operation speed,suppress interference signals in the near field environment.Finally,after studying the near field broadband beamforming method,this paper introduces three beamforming methods aiming at the particularity of wideband signal processing:a conventional delay beamforming method based on time-domain signal processing and two kinds of adaptive broadband beamforming method of ISM algorithm and CSM algorithm based on frequency-domain decomposition.Combining them with simulation experiments,the performance of beam shape,the ability of restraining interference and operating rate of these several methods can be compared.