Flow‐induced noise in merchant ship broadband source levels

TitleFlow‐induced noise in merchant ship broadband source levels
Publication TypeJournal Article
Year of Publication1979
AuthorsWright, E. B.
JournalThe Journal of the Acoustical Society of America
ISBN Number0001-4966
EndNote Rec Number1597

Source level spectra for 14 large merchant ships have been measured with hydrophones at about 400 m from the ships' tracks. The measured broadband levels tend to be fairly constant from 20 or 30 Hz down to 4 or 5 Hz, instead of decreasing. A possible cause of these high measured low-frequency levels is flow-induced noise radiated from the turbulent boundary layer on the ship's hull [E. A. Vecchio and C. A. Wiley, J. Acoust. Soc. Am. 53, 596–601(1975)]. This paper presents results of calculating the radiated flow-induced noise, as received at the experimental ranges. The smooth-plate expressions for boundary layer thickness and source spectral density have been modified to conform to typical hull roughness. The computed levels, above 5 Hz, are generally less than 10 dB from the measured received levels, suggesting that flow-induced noise is an important component of merchant ship radiated noise from about 5 to 20 Hz.