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.
Highlights
1.1 BackgroundSince the earliest times in human history the ocean has provided food, protection, a means for transportation, and trade routes
By having the vehicle use its on board sensors to keep it at a height h above the sea floor the angle from the source to the array is given by θ = tan−1 2h L. While this experiment may allow for the measurement of the propagating field as well as the evanescent field, it requires the development of an Autonomous Underwater Vehicles (AUVs) based low frequency source which may prove difficult given the power constraints on a vehicle
The motivation was the need for site specific sediment data and the monetary and time costs associated with doing so with a traditional experiment involving ships, long towed array and moored assets
Summary
Since the earliest times in human history the ocean has provided food, protection, a means for transportation, and trade routes. The major advance in sonar technology did not happen until the early 20th century when two listening devices where attached to the end of a rotating shaft, providing a sense of the direction of the sound. Systems advanced from having two sensors, to multiple sensors on a single line, and to multiple lines of multiple sensors which gave directionality in bearing as well as depth These systems were adapted by the Navy for surveillance and detection as well as by the surveying industry for oil exploration [4]. Underwater acoustic technology has advanced to the point where the weighted depth lines of ancient sailors have been replaced with electronic precision depth sounders which enable the captain of a vessel to know the depth of the water below his keel, but to know the structure of the ocean bottom. This thesis is a demonstration of the generation of technology in a progression of acoustic oceanography and bottom measurements that stared with the ancient desire to know “what’s down there”
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