SEGJ Technical Conference

Development of a non-contact type surface-wave measurement system (Part 4): Suppression of direct sounds by improving an insulation box

Abstract We have improved a sound insulation box, a major part of the non-contact surface wave measurement system we developed. The box incorporates a single array composed of 12 or 36 microphones at 5 cm intervals. To reduce direct sound noises but also to lighten the weight of the box, we adopted a single array instead of double lines we had employed, and downsized the width of the box. We tightly packed sound absorbing sponges inside the box, and suppressed direct sound noises by closing the space between the bottom of the box and the pavement surface as narrow as possible. Consequently, the system could successfully measure clean leaky surface waves which propagated from the pavement surfaces. The field tests demonstrated the system cleared one of critical gates for practical use.