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3 Hydroacoustics

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Pomiar dźwięków foki szarej

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Malinowski S. J. , Gloza I. , Domagalski J.

Hydroacoustics

2000

tom Vol. 3

177--182

Animals produce a wide range of sounds that can travel at great distances underwater. During the presentation you will listen to the real hydrophone recordings which were made here in Hel. The paper & recordings present the results of sound imitated by grey seals. Signature sounds differ between the individuals. Seals have a well-developed sense of hearing, especially in the water. In the air, their hearing ability is greatly reduced. They have large eyes and their underwater vision is better than a human 's, but even blind mammals are healthy, because the most important sense in the water is hearing, Researchers know that seals have an acute sense of smell on land. This sense is important for mothers identifying their pups. The results of the measurements show that the sound intensity method is worth using, especially in pools , shallow water, and to identify and find the direction of a sound source.

The character of underwater noise radiated by small vessels

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Malinowski S. J. , Gloza I. , Domagalski J.

tom Vol. 4

161--164

This paper presents an overview of our initiatives for underwater noise measurements and their acoustic characteristics, which years ago have been applied. Different kinds of surface ships and more importantly submarines radiate high levels of underwater noise which can be detected and tracked by passive sonars. Hostile navies use these signatures for detection and classification of targets. In many cases, not only a vessel as a specific class of warship, but also even the individual ship within a concrete class can be positively identified. The method of narrow-band filtration of the spectrum' s discrete lines at frequencies up to several H: is the basic standard of passive systems for long-distance detection. To find the source of noise, the level of vibration was also measured by accelerometers. Ship' s very own distinctive acoustic signature radiated at discrete frequencies, excited by the machinery, is easily detected and must be decreased as much as possible. Coherence between underwater sound pressure from a moving vessel and vibration during the same run was made.

Underwater noise radiated by ships, their propulsion and auxiliary machinery, and propellers

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Malinowski S. J. , Gloza I. , Domagalski J.

tom Vol. 4

165--168

These underwater radiated noise and vibration measurements were conducted on a full-scale ship in August 2000. During the trails it was found that several spike noises are dominant. To find the location of high vibration level places and its frequencies, and the machines, which generated high level point noise components, 4 accelerometers were fixed in the engine and auxiliary rooms .We were using this system to find the relationship between certain manoeuvres and the vibration level caused by them. Propellers and engines are usually the major sources of noise in ships but gearboxes can also be significant contributors. The way of mounting of the machines and the resulting vibration of the hull are determining issues in the radiation of underwater noise. Naval Test and Evaluation Acoustic Ranges contain an accurate radiated noise measurement system consisting of a bottom-mounted hydrophone array for sailing condition and a stationary range. The sophisticated digital narrow-band instruments and analogue recorders were used by us.