Equal latency contours and auditory weighting functions for the harbour porpoise (Phocoena phocoena)

Abstract

Loudness perception by human infants and animals can be studied under the assumption that sounds of equal loudness elicit equal reaction times (RTs). Simple RTs of a harbour porpoise to narrowband frequency-modulated signals were measured using a behavioural method and an RT sensor based on infrared light. Equal latency contours, which connect equal RTs across frequencies, for reference values of 150−200 ms (10 ms intervals) were derived from median RTs to 1 s signals with sound pressure levels (SPLs) of 59-168 dB re. 1 μPa and centre frequencies of 0.5, 1, 2, 4, 16, 31.5, 63, 80 and 125 kHz. The higher the signal level was above the hearing threshold of the harbour porpoise, the quicker the animal responded to the stimulus (median RT 98−522 ms). Equal latency contours roughly paralleled the hearing threshold at relatively low sensation levels (higher RTs). The difference in shape between the hearing threshold and the equal latency contours was more pronounced at higher levels (lower RTs); a flattening of the contours occurred for frequencies below 63 kHz. Relationships of the equal latency contour levels with the hearing threshold were used to create smoothed functions assumed to be representative of equal loudness contours. Auditory weighting functions were derived from these smoothed functions that may be used to predict perceived levels and correlated noise effects in the harbour porpoise, at least until actual equal loudness contours become available.

Dose-response relationships for the onset of avoidance of sonar by free-ranging killer whales

“…3). This function is a modified version of the C-and M-weighting functions, but fitted with x as a free parameter instead of a value of 2 to match the steeper slopes of the hearing threshold (Wensveen et al, 2014). The fitted HT (HT in dB re 1 lPa) was then inverted to obtain a weighting function (W in dB re 1 lPa À1 ) as: W(f) ¼ ÀHT(f).…”

Effects of exposure to intermittent and continuous 6–7 kHz sonar sweeps on harbor porpoise (Phocoena phocoena) hearing

“…The frequency-dependent characteristics of these contours show that bottlenose dolphins are more susceptible to highfrequency noise exposures than to low-frequency noise exposures. For harbor porpoises, equal-loudness contours have been proposed based on equal-latency contours (Wensveen et al, 2014); they are similar in shape to the equal-loudness contours of bottlenose dolphins (Finneran and Schlundt, 2013). On the basis of the work of Finneran and Schlundt (2013) and Wensveen et al (2014), harbor porpoise hearing is expected to be more susceptible to exposure to MFAS signals than to low frequency active sonar (LFAS) signals.…”

“…For harbor porpoises, equal-loudness contours have been proposed based on equal-latency contours (Wensveen et al, 2014); they are similar in shape to the equal-loudness contours of bottlenose dolphins (Finneran and Schlundt, 2013). On the basis of the work of Finneran and Schlundt (2013) and Wensveen et al (2014), harbor porpoise hearing is expected to be more susceptible to exposure to MFAS signals than to low frequency active sonar (LFAS) signals. However, knowledge of TTS in harbor porpoises is limited, and little is known about increases in TTS due to fatiguing noise level or duration increases, or about recovery from TTS induced by sound in the 6-7 kHz frequency range.…”

Fast sensory–motor reactions in echolocating bats to sudden changes during the final buzz and prey intercept

“…The bats' reactions require complex processing and motor control, but only took 80-90 ms, i.e., much faster than other nonreflex systems requiring higher order processing of sensory input (35,36). However, the reaction times here are within the range suggested by other echolocation experiments (19,(40)(41)(42). Conceivably, echolocation allows for very short reaction times because the temporal precision of the auditory system far exceeds that of other sensory modalities (43).…”