| We have developed a non-contact type surface wave measurement tool using arrayed microphones for the investigation of pavement structure. The tool comprises a pair of microphone arrays, each of which is composed of a total of 24 microphones aligned at 5 cm intervals. The microphone arrays are suspended 2 cm above the pavement surface in a sound insulation box cart. The air-coupled microphone arrays can detect imperceptible sounds of leaky surface waves masked by overwhelming shot coherent air wave noises. Field measurements demonstrated that the tool could observe the surface waves which showed clear dispersions in the frequency range from 40 Hz to 20 kHz. To confirm whether the dispersion characteristics derived from the observed sounds were valid, we conducted comparative measurements with high-frequency accelerometers adhered to the pavement surface. We had conducted field measurements using the accelerometers on pavements and successfully delineated 2D velocity structures of the pavements. The comparative measurements elucidated that the air-coupled microphone array tool provided basically the same dispersion curves as the surface-adhered accelerometers. In conclusion, the microphone array tool was capable for the continuous or 2D structural investigation of pavements. |
