Abstract: A simple method to calculate sound absorption coefficient of the sound absorbing materials of the automobile cab is proposed. Based on the acoustic impedance arrangement of the sound absorbing materials, the formula for resistivity and porosity flow of the sound absorbing materials is obtained; then Matlab cycle is used to calculate flow resistivity and porosity, and based on the obtained figures, sound absorption coefficient of the sound absorbing materials in the automobile cab can be calculated theoretically; thus providing a simple method for the calculation of sound absorption coefficient of the sound absorbing materials in the automobile cab in theory. At the same time, the relationship of the sound absorption coefficient of the material, the resistivity, porosity and thickness and incident wave frequency of the sound-absorbing material is studied. Under the low frequency, the sound absorption coefficient and porosity and thickness is proportional. When the incident sound wave is in the range of 0-500 Hz, the coefficient of the cab sound absorption material decreases slightly with resistivity but the rate of decline is not significant; with the increasing frequency of incident sound wave, the sound absorption coefficient of the cab sound-absorbing material generally has an upward trend.

Key words: automobile cab;sound absorbing coefficient;flow resistivity;porosity