Underwater Noise Characteristics of Small Ships
Abstract:For years in the Polish Navy extensive measurements have been made of the underwater noise radiated by different kinds of surface ships. The underwater sound measurement in the case being described was performed both for anchored and sailing conditions. To identify the source of noise, the level of vibration was also measured by accelerometers inside each ship section. Radiation at discrete frequencies caused by low frequency hull vibrations excited by the machinery is easily detected and must be reduced as much as possible. The radiated noise spectra show high-level tonal frequencies from propellers and main engines. They vary with the speed of the vessel in a complex manner. The ship's service diesel generator (SSDG) creates a series of harmonics which amplitudes and frequencies are independent of ship speed. This article documents characteristics of the surface ship's underwater radiated noise data. The noise from small vessels elevates the natural ambient noise by 10–40 dB. Third-octave bandwidth analyses are too wide for separation of the individual radiated components of ship noise, and that is why accurate narrow-band spectra (sometimes less than 0.1 Hz) have been made.
Document Type: Research Article
Publication date: 2002-09-01
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- Acta Acustica united with Acustica, published together with the European Acoustics Association (EAA), is an international, peer-reviewed journal on acoustics. It publishes original articles on all subjects in the field of acoustics, such as general linear acoustics, nonlinear acoustics, macrosonics, flow acoustics, atmospheric sound, underwater sound, ultrasonics, physical acoustics, structural acoustics, noise control, active control, environmental noise, building acoustics, room acoustics, acoustic materials, acoustic signal processing, computational and numerical acoustics, hearing, audiology and psychoacoustics, speech, musical acoustics, electroacoustics, auditory quality of systems. It reports on original scientific research in acoustics and on engineering applications. The journal considers scientific papers, technical and applied papers, book reviews, short communications, doctoral thesis abstracts, etc. In irregular intervals also special issues and review articles are published.
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