title: Deep water towed array measurements at close range.
abstract: During the North Pacific Acoustic Laboratory Philippine Sea 2009 experiment, towed array receptions were made from a towed source as the two ships transited from a separation of several Convergence Zones through a Closest Point of Approach at 3 km. A combination of narrowband tones and broadband pulses were transmitted covering the frequency band 79-535 Hz. The received energy arrives from two general paths-direct path and bottom bounce. Bearing-time records of the narrowband arrivals at times show a 35° spread in the angle of arrival of the bottom bounce energy. Doppler processing of the tones shows significant frequency spread of the bottom bounce energy. Two-dimensional modeling using measured bathymetry, a geoacoustic parameterization based upon the geological record, and measured sound-speed field was performed. Inclusion of the effects of seafloor roughness and surface waves shows that in-plane scattering from rough interfaces can explain much of the observed spread in the arrivals. Evidence of out-of-plane scattering does exist, however, at short ranges. The amount of out-of-plane scattering is best observed in the broadband impulse-beam response analysis, which in-plane surface roughness modeling cannot explain.
authors.affiliation: Ocean Acoustical Services and Instrumentation Systems, Inc., 11006 Clara Barton Drive, Fairfax Station, Virginia 22039.
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Heaney
authors.forename: Richard L
authors.initials: RL
authors.lastname: Campbell
authors.forename: James J
authors.initials: JJ
authors.lastname: Murray
authors.forename: Arthur B
authors.initials: AB
authors.lastname: Baggeroer
authors.forename: Eddie K
authors.initials: EK
authors.lastname: Scheer
authors.forename: Ralph A
authors.initials: RA
authors.lastname: Stephen
authors.forename: Gerald L
authors.initials: GL
authors.lastname: D'Spain
authors.forename: James A
authors.initials: JA
authors.lastname: Mercer
mesh_terms: D000162:Acoustics / Q000295:instrumentation; D004301:Doppler Effect; D019015:Geologic Sediments; D008962:Models, Theoretical; D009038:Motion; D009791:Oceanography / Q000295:instrumentation / Q000379:methods*; D009792:Oceans and Seas; D012542:Scattering, Radiation; D012623:Seawater; D012815:Signal Processing, Computer-Assisted; D013016:Sound; D013018:Sound Spectrography; D013499:Surface Properties; D013997:Time Factors; D014159:Transducers; D014872:Water Movements