scope:

The use of AEPs to obtain audiograms from odontocetes (toothed whales) has become increasingly common. The use of sinusoidally amplitude-modulated (SAM) tones to elicit the ASSR is the most typical of the AEP approaches used in determining frequency-specific hearing thresholds in odontocetes. Trains of tone bursts provide an alternative means for eliciting the ASSR, and both approaches are amenable to objective analysis in the frequency domain. This standard establishes methods for the measurement of the ASSR generated by SAM tones and tone-burst trains in odontocetes, including instructions for appropriate stimulus waveforms and stimulus calibration. The standard further establishes configurations for electrode placement and stimulus delivery, and minimum requirements for reporting electrophysiological and acoustical noise.

Data collected according to this standard is to be used in the creation of audiograms for individually tested odontocetes. The data is anticipated for use in interspecies comparisons of hearing abilities and to improve the ability to predict and mitigate the potential impact of underwater sound on odontocetes. It is expected that users of the standard will include scientists interested in marine mammal hearing; users of the data collected according to the standard will include academia, regulators, and government and private agencies required to address the potential impact of human-caused sound on marine mammals. Data collected according to the standard will increase comparability of frequency-specific threshold estimates made by different individuals and laboratories under varying constraints on test conditions. This standard is limited to the determination of frequency-specific hearing thresholds in odontocetes via ASSR evoked potential audiometry; it does not preclude the use of different AEP techniques for studying other aspects of odontocete hearing. None of the procedures described in this standard can be used for monaural hearing tests; all methods described result in binaural stimulation to some degree.