Field Measurements for Traffic Noise Reduction in Highway Tunnels Using Closed-Cell Aluminum Foam Board

Abstract

In order to explore the sound absorption and noise reduction performance of closed-cell aluminum foam in the tunnel, the field test of the sound absorption performance of aluminum foam board was carried out based on the installation of aluminum foam board in the whole line of Haoshanyu Tunnel on Qinglan Expressway. Combined with the existing loudspeaker test and typical tunnel measurements, a new field test method for the noise reduction performance of closed-cell aluminum foam board was proposed for two different working conditions including fixed-point pure tone sound source condition and mobile vehicle sound source condition. The testing results of the new methods were analyzed, and it showed that the closed-cell aluminum foam has good sound absorption property at the frequency spectra between 250 Hz and 1000 Hz, and the farther away from the sound source, the better the sound absorption effect. In the research on the noise reduction effect of actual vehicle, it was found that the insertion loss of the closed-cell foam aluminum board is about 4 dB(A), which indicated that the closed-cell aluminum foam can play a certain noise reduction effect in the tunnel.

Fabrication, Processing, Properties, and Applications of Closed-Cell Aluminum Foams: A Review

“…After drilling holes, the connected cells of aluminum foams form a Helmholtz resonant sound absorption structure [168], which creates strong friction between the intensely vibrating air and the connected cells, and results in more sound energy consumption [37]. It can effectively absorb sound waves with frequencies of 250~5000 Hz [37,169]. Sound absorption of closed-cell aluminum foams can be improved by drilling holes [170], setting a cavity at the back of aluminum foams [22], or a certain degree of compression [171].…”