Abstract:

In order to study the acoustic absorption properties of activated carbon fiber felts with gradient structure, five viscose based activated carbon fiber felts with different densities were selected and coupled into gradient structure. The impedance tube was used to test the normal incidence acoustic absorption coefficient of activated carbon fiber felts with gradient structure within 250-6 300 Hz accoustic waves. Factors impacting on the acoustic absorption performance of samples were explored by analyzing the effect of gradient direction, density and structures. The results show that under the same density, the acoustic absorption performance of the single structure at low frequency is better than that of the positive gradient structure, but worse than that of the inverted gradient structure. In the high frequency band, the acoustic absorption performance of the single structure is worse than that of the positive gradient structure, but better than that of the inverted gradient structure. In the case of different densities, the acoustic absorption coefficient increases as the total density of the gradient structure is increased in the low frequency band. In the high frequency band, the acoustic absorption coefficient decreases as the density of the first layer of the gradient structure is increased. As the density of the first layer increases, the first resonant frequency moves towards low direction. As the total density increases, the first resonance absorption coefficient increases.

Key words: activated carbon fiber, gradient structure, acoustic absorption coefficient, the first resonance frequency, sound absorbing material