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Noise level, distance, and potential effects on birds from a noise source (traffic noise). The zones indicate distances over which specific effects will be experienced by a bird. In Zone 1 close to the noise source, potential effects include permanent threshold shift (PTS), temporary threshold shift (TTS), and other behavioral or physiological effects. In Zone 4, furthest from the noise source, we would expect only other effects. (Dooling & Popper 2007; Dooling & Blumenrath 2014).
