Fluctuations of resolved acoustic multipaths at short range in the ocean

Worcester, Peter F.; Williams, Gordon O.; Flatté, Stanley M.

doi:10.1121/1.2018848

Cited by 2 publications

(2 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the 1970s, the main effort to understand ocean acoustic WPRM focused on relatively high acoustic frequency and short-range experiments using broadband explosive sources and narrowband transducers. A large amount of data addressing the spatial and temporal statistics of fluctuations were collected [34,31,35,41,86,40,43,26].…”

Section: Context and Motivation For This Study 121 Acoustic Fluctuamentioning

confidence: 99%

Effects of internal waves on low frequency, long range, acoustic propagation in the deep ocean

Xu¹

2007

View full text Add to dashboard Cite

This thesis covers a comprehensive analysis of long-range, deep-ocean, low-frequency, sound propagation experimental results obtained from the North Pacific Ocean. The statistics of acoustic fields after propagation through internal-wave-induced sound-speed fluctuations are explored experimentally and theoretically.The thesis starts with the investigation of the North Pacific Acoustic Laboratory 98-99 data by exploring the space-time scales of ocean sound speed variability and the contributions from different frequency bands. The validity of the Garret & Munk internal-wave model is checked in the upper ocean of the eastern North Pacific. All these results impose hard bounds on the strength and characteristic scales of sound speed fluctuations one might expect in this region of the North Pacific for both internal-wave band fluctuations and mesoscale band fluctuations.The thesis then presents a detailed analysis of the low frequency, broadband sound arrivals obtained in the North Pacific Ocean. The observed acoustic variability is compared with acoustic predictions based on the weak fluctuation theory of Rytov, and direct parabolic equation Monte Carlo simulations. The comparisons show that a resonance condition exists between the local acoustic ray and the internal wave field such that only the internal-waves whose crests are parallel to the local ray path will contribute to acoustic scattering: This effect leads to an important filtering of the acoustic spectra relative to the internal-wave spectra. We believe that this is the first observational evidence for the acoustic ray and internal wave resonance.Finally, the thesis examined the evolution with distance, of the acoustic arrival pattern of the off-axis sound source transmissions in the Long-range Ocean Acoustic Propagation EXperiment. The observations of mean intensity time-fronts are compared to the deterministic ray, parabolic equation (with/without internal waves) and (one-way coupled) normal mode calculations. It is found the diffraction effect is dominant in the shorter-range transmission. In the longer range, the (internal wave) scattering effect smears the energy in both the spatial and temporal scales and thus has a dominant role in the finale region.

show abstract

Section: Context and Motivation For This Study 121 Acoustic Fluctuamentioning

confidence: 99%

Effects of internal waves on low frequency, long range, acoustic propagation in the deep ocean

Xu¹

2007

View full text Add to dashboard Cite

show abstract

“…In both deep ocean and shallow water continental shelf environments, a major source of acoustic field scintillation is internal waves [7,8,9]. Early efforts to describe signal scintillation statistics in the ocean were based on multipath theory, with the resultant field being the sum of multiple random phase components [10,11,12].…”

Section: Introductionmentioning

confidence: 99%

Probability distribution for energy of saturated broadband ocean acoustic transmission: Results from Gulf of Maine 2006 experiment

Tran¹,

Ratilal²

2013

Proceedings of Meetings on Acoustics

View full text Add to dashboard Cite

The probability distribution of ocean-acoustic broadband signal energy after saturated multipath propagation is derived using coherence theory. The frequency components obtained from Fourier decomposition of a broadband signal are each assumed to be fully saturated with energy spectral density that obey the exponential distribution with 5.6 dB standard deviation and unity scintillation index. When the signal bandwidth and measurement time are larger than the correlation bandwidth and correlation time respectively of its energy spectral density components, the broadband signal energy obtained by integrating the energy spectral density across the signal bandwidth then follows the Gamma distribution with standard deviation smaller than 5.6 dB and scintillation index less than unity. The theory is verified with broadband transmissions in the Gulf of Maine shallow water waveguide in the 300-1200 Hz frequency range. The standard deviations of received broadband signal energies range from 2.7 to 4.6 dB for effective bandwidths up to 42 Hz, while the standard deviations of individual energy spectral density components are roughly 5.6 dB. The energy spectral density correlation bandwidths of the received broadband signals are found to be larger for signals with higher center frequencies and are roughly 10% of each center frequency.

show abstract

Fluctuations of resolved acoustic multipaths at short range in the ocean

Cited by 2 publications

References 0 publications

Effects of internal waves on low frequency, long range, acoustic propagation in the deep ocean

Effects of internal waves on low frequency, long range, acoustic propagation in the deep ocean

Probability distribution for energy of saturated broadband ocean acoustic transmission: Results from Gulf of Maine 2006 experiment

Contact Info

Product

Resources

About