In the traditional sonar system, ocean ambient noise is regarded as a hindrance to the detection of a target object, since it distorts the sound characteristics of the target signal. However, much attention has been paid to the new idea of detecting objects by using ocean ambient noise affirmatively. This concept is called acoustic daylight imaging. Each pixel of the target image is mapped by monochrome or pseudo-color to represent acoustic intensity in each direction. This intensity is obtained by the reflecting or scattering wave of the target object, using the ocean background noise as the sound source. The authors have tried to detect a silent target object using ambient noise by employing a wideband beamformer constructed of an array of receivers. In the experimental results in air, we successfully detected the silent target object in the acoustic noise field generated by many transducers with the line array of receiver, by applying delay-sum array method. In this paper, some experimental results are reported. The ocean ambient noise is simulated by transducers decentralized to 56 points in air. The target object arranged in the noise field is detected using the wideband beamformer.

View full abstract