A device and method for measuring characteristic impedance and complex wave number of acoustic materials

Abstract

The invention discloses a device and a method for measuring the characteristic impedance and the complex wave number of an acoustic material. The device comprises an acoustic tube, an impulsive sound source, a microphone, a power amplifier, a signal conditioner, an adapter and a data acquisition device, wherein the acoustic tube consists of a section of large-diameter cylindrical tube, a conical tube and a small-diameter cylindrical tube which are fixedly connected with one another coaxially; three through holes which are vertical to the center axis of the small-diameter cylindrical tube are formed in the side wall of the small-diameter cylindrical tube; the impulsive sound source is arranged in the large-diameter cylindrical tube; and a back cover is in threaded connection with the outer end of the small-diameter cylindrical tube. The method comprises the following steps of: firstly, acquiring a frequency response function of a whole measuring system; secondly, acquiring required excitation signals of the impulse sound source, and exciting the measurement of the impulsive sound source to obtain sound pressures and vibration velocities of front and rear end surfaces of a sample to be tested; and finally, calculating the characteristic impedance and the complex wave number of the sample to be tested. By adopting the method, the problem that the measurement at a low-frequency band is not accurate enough when the characteristic impedance and the complex wave number of a high-flow-resistance material are measured by using the conventional double-cavity method and the conventional double-thickness method is solved.

Description

technical field [0001] The invention relates to the technical field of acoustic material testing, in particular to a device and a measuring method for measuring the characteristic impedance and complex wave number of an acoustic material. Background technique [0002] In the field of sound tube acoustic testing, the characteristic impedance and complex wave number measurement methods of acoustic materials generally adopt the double cavity method and double thickness method. The double cavity method obtains different material surface impedance values ​​by changing the depth of the cavity behind the material, and then according to The calculation formula is solved to obtain the characteristic impedance and complex wave number of the material. The principle of double-thickness measurement is similar to the double-cavity method, and the above parameters are also obtained based on the change of the surface impedance value of the material when two materials with different thicknes...

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Problems solved by technology

Two microphones can be used to exchange measurements to eliminate the mismatch between the two microphones, and the single-microphone method can also be used to measure sequentially, so there will be no phase and amplitude mismatch problems, but it will increase the test time and make the test work cumbersome

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