基于时间延迟的汽车驾驶室吸声系数测量研究

The Research of Sound Absorption Coefficient in Automobile Cabs Based on Time Delay

以汽车发动机噪声辐射能量分布为参考,以其实际使用的某一吸声材料为测试对象,将两个麦克风等间距布置在吸声材料的正前方,利用麦克风分别测得麦克风所在位置的声压数值,将所测得的声压进行拉氏变换,再根据两麦克风之间测得声压的时间延时得到声波的反射系数,最后利用声波的反射系数推导出吸声系数。实验表明:利用该方法测量得到的吸声系数在声波频率较低时与驻波管法以及混响室法测量得到的吸声系数基本一致,在所参考汽车发动机噪声辐射能量分布情况下,基于时间延迟的吸声系数测量更快捷,结果具有较好的可靠性。

With the noise radiation energy distribution of an automobile engine as the reference, and the sound- absorbing material which is actually used as the test object, the research is carried out in the following steps： firstly, two microphones were placed equidistantly in front of the sound-absorbing material, then the sound pressure values at the locations of the two microphones were measured respectively by using the microphones, and Laplace transform was made for the measured sound pressure; secondly, the reflection coefficient of the sound absorbing- material was obtained according to the time delay of sound pressure measured between two microphones; finally, the sound absorption coefficient was derived by using the reflection coefficient of the sound-absorbing material. Experiment results show that the sound absorption coefficient measured by this method is nearly the same as those measured by standing wave tube and reverberation room methods in low frequency range. Taking the automobile engine noise radiation energy distribution as reference, the proposed method to measure sound absorption coefficient based on time delay is fast and reliable.