Investigation of ocean acoustics using autonomous instrumentation to quantify the water-sediment boundary properties

Abstract

Several noise criteria methods commonly used in architectural acoustics have been quantitatively related to noise perception and task performance under a variety of ventilation systems-induced background noise conditions. Noise criteria, balanced noise criteria, room criteria, room criteria mark II, and A-weighted equivalent sound pressure level were examined. The first phase of the project included noise conditions controlled to be non-time-varying and nontonal, with neutral, rumbly, roaring, or hissy characteristics. An intermediate study examined exposure time length and types of performance tasks used. The final phase included noise conditions containing various levels of discrete tones from 120 to 595 Hz. Under each noise, subjects completed performance tasks and perception questionnaires. Results indicate task performance was significantly affected by perception of noise, but this relationship was not fully demonstrated by the criteria systems analyzed. The five criteria were generally well suited in describing subjective loudness perception, but some discrepancies in criteria spectral quality ratings and subjective perception existed. Finally, perception of annoyance changed based on the frequency and prominence of tones in noise, but these changes were not reflected in the criteria level or spectral quality ratings. Modifications to the existing criteria are recommended.

Model-Based Processing for a Short Towed Array

“…The Nantucket Sound experiments [2,3] consisted of an AUV towed array system navigating at a constant depth radially out from a source deployed from a small ship. Figure 1 shows a schematic of the experimental configuration.…”

Sound Speed and Attenuation in Multiphase Media

“…During the past year several major tasks have been performed. Holmes [3,8] has compared this theory to experimental results for which the environmental conditions and the geophysical properties were known. While the theory predicts a power-law dependence with an exponent of 2, the experiments con-ducted in areas with similar sediments and environmental conditions yielded an exponent on average of approximately 1.8 with values of the attenuation constant consistent with Hamilton [6] at 1 kHz.…”

“…In this experiment characterization of the bottom properties used the synthetic-aperture Hankel transform described by Frisk et al [7] an again by Holmes [8]. The details of the requisite signal processing to form a long array using an autonomous-vehicle towed array are given in reference [8,9].…”

“…The details of the requisite signal processing to form a long array using an autonomous-vehicle towed array are given in reference [8,9]. The basic method was to determine the horizontal wave-number spectrum that is an approximation to the Green's function;…”

“…During the past year several major tasks have been performed. Holmes [3,8] has compared this theory to experimental results for which the environmental conditions and the 1 …”