Estimating bottlenose dolphin (Tursiops truncatus) hearing thresholds from single and multiple simultaneous auditory evoked potentials

Hearing thresholds can be used to quantify one's hearing ability. In various masking conditions, hearing thresholds can vary depending on the auditory cues. With comodulated masking noise and interaural phase disparity (IPD), target detection can be facilitated, lowering detection thresholds. This perceptual phenomenon is quantified as masking release: comodulation masking release (CMR) and binaural masking level difference (BMLD). As these measures only reflect the low limit of hearing, the relevance of masking release at supra-threshold levels is still unclear. Here, we used both psychoacoustic and electro-physiological measures to investigate the effect of masking release at supra-threshold levels. We investigated whether the difference in the amount of masking release will affect listening at supra-threshold levels. We used intensity just-noticeable difference (JND) to quantify an increase in the salience of the tone. As a physiological correlate of JND, we investigated late auditory evoked potentials (LAEPs) with electroencephalography (EEG). The results showed that the intensity JNDs were equal at the same intensity of the tone regardless of masking release conditions. For LAEP measures, the slope of the P2 amplitudes with a function of the level was inversely correlated with the intensity JND. In addition, the P2 amplitudes were higher in dichotic conditions compared to diotic conditions. Estimated the salience of the target tone from both experiments suggested that the salience of masked tone at supra-threshold levels may only be beneficial with BMLD.

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Masked hearing thresholds for a bottlenose dolphin (Tursiops truncatus) and white whale (Delphinapterus leucas) in the far field and hydrodynamic near field

The Journal of the Acoustical Society of America ◽

10.1121/1.428956 ◽

2000 ◽

Vol 107 (5) ◽

pp. 2785-2786

Author(s):

James J. Finneran ◽

Sam H. Ridgway

Keyword(s):

Bottlenose Dolphin ◽

Tursiops Truncatus ◽

Near Field ◽

Delphinapterus Leucas ◽

Far Field ◽

White Whale ◽

Hearing Thresholds

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Forward masking in a bottlenose dolphin Tursiops truncatus : Dependence on azimuthal positions of the masker and test sources

10.1101/2022.01.11.475800 ◽

2022 ◽

Author(s):

Vladimir Popov ◽

Dmitry Nechaev ◽

Alexander Ya. Supin ◽

Evgeniya Sysueva

Keyword(s):

Auditory System ◽

Bottlenose Dolphin ◽

Tursiops Truncatus ◽

Auditory Evoked Potentials ◽

Forward Masking ◽

Source Position ◽

Sound Sources ◽

Head Surface ◽

Release From Masking ◽

Lateral Head

Forward masking was investigated by the auditory evoked potentials (AEP) method in a bottlenose dolphin Tursiops truncatus using stimulation by two successive acoustic pulses (the masker and test) projected from spatially separated sources. The positions of the two sound sources either coincided with or were symmetrical relative to the head axis at azimuths from 0 to ±90°. AEPs were recorded either from the vertex or from the lateral head surface next to the auditory meatus. In the last case, the test source was ipsilateral to the recording side, whereas the masker source was either ipsi- or contralateral. For lateral recording, AEP release from masking (recovery) was slower for the ipsi- than for the contralateral masker source position. For vertex recording, AEP recovery was equal both for the coinciding positions of the masker and test sources and for their symmetrical positions relative to the head axis. The data indicate that at higher levels of the auditory system of the dolphin, binaural convergence makes the forward masking nearly equal for ipsi- and contralateral positions of the masker and test.

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