Comodulation detection differences in the hooded crow (Corvus corone cornix), with direct comparison to human subjects.
Envelope modulations have been shown important in determining the effectiveness of masking noises. For example, the threshold for detecting a signal flanked by maskers is lower if the maskers and the signal are modulated with different envelopes, rather than the same envelope (comodulation). This threshold change is called the comodulation detection difference (CDD). CDDs were studied in two wild-caught hooded crows, using a 1.5 kHz signal and two maskers at 0.9 and 2.1 kHz, presented at an overall level of 55 dB SPL (re 20 microPa). For direct comparison with human psychophysics, three human subjects were tested in the same setup. CDDs averaged 15 dB for the two crow subjects and 11 dB for the human subjects. The species difference between average CDDs was insignificant. The significance of the CDD effect in a natural setting is discussed.
Jensen
Kenneth Kragh
KK
Institute of Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark. kkj@jensenkk.net
D000162:Acoustics; D000819:Animal Communication; D000818:Animals; D001309:Auditory Threshold; D046368:Crows / Q000502:physiology*; D006801:Humans; D010470:Perceptual Masking; D011601:Psychophysics