L. E. Wysocki, S. Amoser and F. Ladich (2007): Diversity in ambient noise
in European freshwater habitats: Noise levels, spectral profiles, and
impact on fishes. J. Acoust. Soc. Am. 121(5), pp. 2559-2566.
Abstract: The detectability of acoustic signals depends on the hearing
abilities of receivers and the prevailing ambient noise in a given
habitat. Ambient noise is inherent in all terrestrial and aquatic habitats
and has the potential to severely mask relevant acoustic signals. In order
to assess the detectability of sounds to fishes, the linear equivalent
sound pressure levels (LLeq) of twelve European freshwater habitats were
measured and spectra of the ambient noise recordings analyzed. Stagnant
habitats such as lakes and backwaters are quiet, with noise levels below
100 dB re 1 µPa (LLeq) under no-wind conditions. Typically, most
environmental noise is concentrated in the lower frequency range below 500
Hz. Noise levels in fast-flowing waters were typically above 110 dB and
peaked at 135 dB (Danube River in a free-flowing area). Contrary to
stagnant habitats, high amounts of sound energy were present in the high
frequency range above 1 kHz, leaving a low-energy “noise window” below 1
kHz. Comparisons between the habitat noise types presented here and prior
data on auditory masking indicate that fishes with enhanced hearing
abilities are only moderately masked in stagnant, quiet habitats, whereas
they would be considerably masked in fast-flowing habitats.
Kind regards
Sonja Amoser
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