Realization Of Adaptive Active Sound Absorption Device And Application In Traveling Wave Tube Measurement

Transfer function method is a common method for establishing the traveling wave field in the sound tube to measure the acoustic performance of material.However,the deficiency is the transfer function must to be re-measured when the measurement frequency need to be changed.And more,the checking procedure of traveling wave field in the sound tube is essential before measuring the acoustic performance of the material.If it is not an accurate traveling wave field,it is necessary to correct the secondary sound source signal until the traveling wave field meets the requirements.In order to resolve these problems,an adaptive control method for generating the plane traveling waves has been proposed in this paper.Using the amplitude and phase difference of sound pressures which have been measured by the two hydrophones between the secondary sound source and the material as the objective function in the adaptive algorithm,the amplitude and phase of the secondary sound source could be obtained by the adaptive control system in frequency domain.When the traveling wave field is formed,the acoustic properties of the material could be measured at the same time.With this method,the procedure of testing the traveling wave field is omitted.If the state of the main sound source changes,the signal form of the secondary sound source can be changed immediately.Therefore,the efficiency of the material measurement has been improved.In addition,theoretically,this method can get the most matching signal form of the secondary sound source,so the accuracy of this method is very high.Simulation and experimental results in this paper show that,the measurement absolute error is below 0.2 within the frequency range 125Hz-4000Hz.