Effect of received beam width on passive detection of silent target using ambient noise

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. The authors have attempted to detect a silent target object using ambient noise by employing a wide-band beamformer consisting with an array of receivers. In the experimental results obtained in air, we applied the delay-sum array method to successfully detect the silent target object in the acoustic noise field generated by many transducers with a line array of receivers. In this paper, some experimental results of the effect of the beam width formed by the wide-band beamformer on target detection are reported. The ocean ambient noise is simulated by transducers decentralized to many points in air. The spherical target object is detected by changing the number of receivers. The beam width is compared with the angle subtended by the spherical target at the center of the receiver array.