Position of an acoustic window in a beluga whale: Computation based on auditory evoked potential latencies

Abstract

In a beluga whale, the positions of sound receiving areas on the head surface were determined by comparing the acoustic delays from different sound source positions. For this investigation, auditory evoked potentials (AEPs) in response to short tone pips were recorded. Latencies of the first AEP wave that presumably reflected the activity of the auditory nerve were measured at different sound source azimuths. For AEPs of equal amplitudes, the difference in AEP latencies was attributed to the difference in the acoustic delays. These delay differences were used to compute the azimuths of sound receiving points. Measurements were conducted at frequencies from 22.5 to 90 kHz in half-octave steps. At all stimulus frequencies, the receiving points were located 24–38 cm caudal of the melon tip, which is near a proximal part of the lower jaw. Thus, the results indicated the latero-mandibular acoustic window. Possible causes for not finding a lateral or ventro-mandibular window are discussed.

Numerical-modeling-based investigation of sound transmission and reception in the short-finned pilot whale (Globicephala macrorhynchus)

“…In addition, sound-reception channels in which the solid mandible may play a significant role were introduced in both the experiments and numerical models (Castellote et al, 2014;Mooney et al, 2008;Mooney et al, 2015;Mooney et al, 2018;Song et al, 2018). These results indicate that the entire head may function as an antenna system for sound reception (Popov et al, 2019).…”

“…Using a relatively lower-peak-frequency (20 kHz) sound pulse in the current simulations, we showed that the mandible-mandibular pathway is also reliable for lower-frequency acoustic stimuli, though in a different species. The TPC is accessible to sounds propagating through various pathways, and the entire head may function as a volume antenna to conduct sounds as acoustic cues for hearing (Popov et al, 2019). Further studies are needed to quantify the respective contributions of these pathways in hearing.…”

“…Sounds can reach the odontocetes' ear complex via various pathways (Norris 1964(Norris , 1968Cranford et al, 2008;Song et al, 2018;Popov et al, 2019). The external mandibular fat located between the skin and a thin portion of the posterior mandible known as the "pan-bone" constitutes an important sound entrance.…”

Sound Reception in the Yangtze Finless Porpoise and Its Extension to a Biomimetic Receptor

“…These aggregations showed the complexity of acoustic windows in odontocetes. Though the most sensitive areas (the positions of acoustic windows) may have been demonstrated in many species [ 22 , 23 , 24 , 25 , 27 ], there might be other sound-reception paths that have not been addressed in detail as well as the roles of the various structures in these paths. The head as a whole may be considered a volume antenna [ 15 , 27 ], and thus, the roles of the various structures, including the mandible, the mandibular fats, soft tissue, and skull, in conducting sounds to the ear complex require additional work to elucidate.…”

Dual sound reception apparatus in protocetid whales

“…tympanic ligament), and is probably no longer functional in an acoustic point of view (Lillie 1910;Fraser & Purves 1960a,b;McCormick et al 1970;Fleischer 1978;Ekdale et al 2011;Yamato et al 2012;Rehorek et al 2019). Thus, in extant cetacean, the sound reaches the middle ear by other pathways, that are, to date, not clearly understood (Popov & Supin 2007;Cranford et al 2008aCranford et al ,b, 2010Yamato et al 2012;Mooney et al 2012Mooney et al , 2015Popov et al 2016Popov et al , 2019Ryabov 2016;Cranford & Krysl 2018;Sysueva et al 2018;Tubelli et al 2018). One of the main underwater hearing pathways in odontocetes (i.e.…”