Ambient noise measurements from 100 Hz to 80 kHz in an Alaskan fjord.
Measurements covering a broad frequency range from 100 Hz to 80 kHz have been made in Behm Canal, Alaska. This site represents a fairly deep embayment (400 m) with a soft bottom (porosity of about 0.8) and, hence, the noise detected at the hydrophones is affected negligibly by multipath contributions except possibly at the lowest frequencies. Data were gathered over a wide range of wind speeds (0 to 15 m/s) and during periods of rain and snow. Several unique and noteworthy results were obtained. Foremost was the observation that the wind-generated noise level measured during the winter was approximately 5 dB lower than during the summer for the same wind speeds and air-sea temperature differences (air temperature about the same as or colder than the sea surface). The summer data agree well with the most recent published measurements and are approximately 2 dB higher than the standard Knudsen/Wenz reference spectra. It appeared that below-freezing air temperatures and snow were responsible for the 5 dB offset between the summer and winter data. Most reported wind noise measurements are restricted to frequencies less than 20 kHz. Those that go beyond this frequency display a noticeable hump above the usual--17 dB/decade power-law slope, and the Behm Canal measurements show that this hump continues to 80 kHz where the spectrum rejoins the extension of the canonical power-law slope.
McConnell
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Areté Associates, La Jolla, California 92038.
Schilt
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Dworski
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D000162:Acoustics; D000413:Alaska; D006801:Humans; D009622:Noise; D009792:Oceans and Seas; D012621:Seasons; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D013018:Sound Spectrography / Q000295:instrumentation*; D014867:Water; D014887:Weather; D014919:Wind
D014867:Water