- The amount (or the process) by which the threshold of audibility for one sound is raised
by the presence of another (masking) sound.
- Increases in noise levels can decrease the ability of an animal to detect
biologically important sound when the increased noise level rises above the
level of sound for which the animal is listening. This effect is commonly known
as masking. Masking of significant sounds (e.g., calls of other animals,
predators, sounds of hazards, such as approaching boats, etc.) can occur when
ambient noise levels increase. Marine mammals have evolved in the highly
variable noise environment of the ocean, and presumably are well adapted for
tolerating the natural variations in ocean noise that could at times cause
masking. However, the determination of an animal's ability to tolerate changes
in noise levels requires a better understanding of: 1) the functional importance
of faint sound signals from the same species, predators, prey, and other natural
sources; 2) signal detection abilities of marine mammals in the presence of
background noise, including directional hearing abilities at frequencies where
masking is an issue; and 3) abilities of marine mammals to adjust the
intensities and perhaps frequencies and timing of emitted sounds to minimize
masking effects.
Source: [http://www.firstgov.gov/fgsearch/resultstrack.jsp?sid=144785609&url=http://www.nmfs.noaa.gov/prot_res/readingrm/Applications/Stein_EA_final_12-23-03.doc Outline for Acoustics Environmental Assessment]
[[Category: Acoustics]]