Methods And Applications Of Sound Absorption And Insulation Measurements Based On Transfer Functions

Sound absorption and insulation is the acoustical characteristic of material. Measurement of sound absorption and insulation has an important significance in noise control and acoustical design. This paper aims to develop sound absorption and insulation real-time measurement system based on impedance tube, which will be applied in measurement in situ and product line.In this paper, room sound field theory as the basis of measurement based on reverberation chamber and waveguide theory as the basis of measurement based on impedance tube are introduced. Noise control in tube using BPNN is simulated by MATLAB. Reverberation room method and standing wave ratio method for measurement in air are introduced. Free field method and standing wave ratio method for underwater acoustic measurement is presented. Transfer function method is shown in detail. The application of vector hydrophone in underwater sound absorption coefficient measurement is discussed. Reverberation room method for sound insulation measurement is presented, and the sound transmission loss of aluminum plate is simulated by using AutoSEA. Sound transmission loss measurement using four microphones in impedance tube is studied.In this paper, real-time measurement systems of sound absorption coefficient and sound transmission loss based on impedance tube is developed by virtual instruments technique and LabVIEW. Problems such as system frequency response interference are solved. The characteristic of transfer function's phase is analyzed and phase aberration after averaging is eliminated. Measurement results show that this measurement system is satisfied with application requirement, which is meaningful to real-time measurement in situ.