title: Bottom interacting sound at 50 km range in a deep ocean environment.
abstract: Data collected during the 2004 Long-range Ocean Acoustic Propagation Experiment provide absolute intensities and travel times of acoustic pulses at ranges varying from 50 to 3200 km. In this paper a subset of these data is analyzed, focusing on the effects of seafloor reflections at the shortest transmission range of approximately 50 km. At this range bottom-reflected (BR) and surface-reflected, bottom-reflected energy interferes with refracted arrivals. For a finite vertical receiving array spanning the sound channel axis, a high mode number energy in the BR arrivals aliases into low mode numbers because of the vertical spacing between hydrophones. Therefore, knowledge of the BR paths is necessary to fully understand even low mode number processes. Acoustic modeling using the parabolic equation method shows that inclusion of range-dependent bathymetry is necessary to get an acceptable model-data fit. The bottom is modeled as a fluid layer without rigidity, without three dimensional effects, and without scattering from wavelength-scale features. Nonetheless, a good model-data fit is obtained for sub-bottom properties estimated from the data.
authors.affiliation: Applied Ocean Physics and Engineering Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA. ilya@whoi.edu
authors.forename: Ilya A
authors.initials: IA
authors.lastname: Udovydchenkov
authors.forename: Ralph A
authors.initials: RA
authors.lastname: Stephen
authors.forename: Timothy F
authors.initials: TF
authors.lastname: Duda
authors.forename: S Thompson
authors.initials: ST
authors.lastname: Bolmer
authors.forename: Peter F
authors.initials: PF
authors.lastname: Worcester
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Dzieciuch
authors.forename: James A
authors.initials: JA
authors.lastname: Mercer
authors.forename: Rex K
authors.initials: RK
authors.lastname: Andrew
authors.forename: Bruce M
authors.initials: BM
authors.lastname: Howe
mesh_terms: D000162:Acoustics / Q000295:instrumentation; D003198:Computer Simulation; D019015:Geologic Sediments; D008962:Models, Theoretical; D009038:Motion; D009716:Numerical Analysis, Computer-Assisted; D009792:Oceans and Seas; D012815:Signal Processing, Computer-Assisted; D013016:Sound; D013018:Sound Spectrography; D013997:Time Factors; D014867:Water
chemical_list: D014867:Water