Sound absorption and insulation property of closed-cell aluminum foam

The closed-cell aluminum foams （specimen p=0.31 g/cm^3, diameter of 100 nun, and thickness of 20 mm for sound absorption testing; specimen p=0.51 g/cm^3, length of 1 240 mm, width of 1 100 mm, and thickness of 30 mm for sound insulation testing） were prepared by the method of molten body transitional foaming process. Its sound absorption property under frequency of 160-2 000Hz and the sound insulation property under frequency of 100-4 000 Hz were tested. The sound absorption results show that the sound absorption property is much better under middle frequencies than that under low and high frequencies. The sound absorption coefficient climbs when frequency increases from 160 Hz to 800 Hz and then drops when frequency is increased from 800 Hz to 2 000 Hz. The function of the sound absorption mainly depends on the Helmholtz resonator, the microphone as well as cracks of closed-cell aluminum foam. The sound insulation experiments show that the sound reduction index （R） is small under low frequencies, and large under high frequencies; the weighted sound reduction index （Rw） and the highest sound reduction index （R） can reach around 30.8 dB and 43 dB, respectively.