title: Reverberation clutter induced by nonlinear internal waves in shallow water.
abstract: Clutter is related to false alarms for active sonar. It is demonstrated that, in shallow water, target-like clutter in reverberation signals can be caused by nonlinear internal waves. A nonlinear internal wave is modeled using measured stratification on the New Jersey shelf. Reverberation in the presence of the internal wave is modeled numerically. Calculations show that acoustic energy propagating near a sound speed minimum is deflected as a high intensity, higher angle beam into the bottom, where it is backscattered along the reciprocal path. The interaction of sound with the internal wave is isolated in space, hence resulting in a target-like clutter, which is found to be greater than 10 dB above the mean reverberation level.
authors.affiliation: Applied Physics Laboratory, University of Washington, 1013 Northeast 40th Street, Seattle, Washington 98105-6698 frank@apl.washington.edu, djtang@apl.washington.edu.
authors.forename: Frank S
authors.initials: FS
authors.lastname: Henyey
authors.forename: Dajun
authors.initials: D
authors.lastname: Tang
mesh_terms: D000162:Acoustics; D016477:Artifacts; D003198:Computer Simulation; D009038:Motion; D017711:Nonlinear Dynamics; D009716:Numerical Analysis, Computer-Assisted; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D013016:Sound; D013018:Sound Spectrography; D013997:Time Factors; D014732:Vibration; D014867:Water
chemical_list: D014867:Water