Model predictions for bone conduction perception in the human

Abstract

Five different pathways are often suggested as important for bone conducted (BC) sound: (1) sound pressure in the ear canal, (2) inertia of the middle ear ossicles, (3) inertia of the inner ear fluid, (4) compression of the inner ear space, and (5) pressure transmission from the skull interior. The relative importance of these pathways was investigated with an acousticimpedance model of the inner ear. The model incorporated data of BC generated ear canal sound pressure, middle ear ossicle motion, cochlear promontory vibration, and intracranial sound pressure. With BC stimulation at the mastoid, the inner ear inertia dominated the excitation of the cochlea but inner ear compression and middle ear inertia were within 10 dB for almost the entire frequency range of 0.1 to 10 kHz. Ear canal sound pressure gave little contribution at the low and high frequencies, but was around 15 dB below the total contribution at the mid frequencies. Intracranial sound pressure gave responses similar to the others at low frequencies, but decreased with frequency to a level of 55 dB below the total contribution at 10 kHz. When the BC inner ear model was evaluated against AC stimulation at threshold levels, the results were close up to approximately 4 kHz but deviated significantly at higher frequencies. 3 Highlights• A model for BC simulates the contribution from 5 components.• The inner ear compression and inertia and middle ear inertia are most important.• The contribution from intracranial sound pressure is insignificant at higher frequencies.• The model provides similar BM excitation for AC and BC threshold stimulation up to 4 kHz. KeywordsBone conduction, inner ear model, fluid inertia, inner ear compression, middle ear inertia

Simulation of the power transmission of bone-conducted sound in a finite-element model of the human head

“…Experimental results in humans by Sohmer et al (2000) also reported that BC sound power from a vibration transducer applied directly to the dura caused sound perception which was attributed to sound transmission through the CSF. Moreover, experiments in human cadaver heads have shown that there is a sound pressure inside the skull during BC stimulation (Roosli et al 2016;Sim et al 2016), but it was estimated not to be important for BC hearing in the human with a normal functioning ear (Stenfelt 2016). However, it is not clear how the BC sound in the skull bone and skull interior interacts.…”

Effectiveness of Bone Conduction Stimulation Applied Directly to the Otic Capsule Measured at Promontory: Assessment in Cadavers

“…It is still impossible to predict the effect of stimulation at a set amplification, frequency, and site, so any simulations or theoretical modeling prove to be imprecise. This is due to an unusual complexity of phenomena occurring during the process of sound transmission via BC to the organ of Corti in the inner ear [Freeman et al, 2000;Stenfelt, 2006Stenfelt, , 2016Stenfelt and Goode, 2005a;Tonndorf, 1966;vonBékésy, 1960;Yoshida and Uemura, 1991], already mentioned in the Introduction.…”

“…The obtained results should be interpreted cautiously, as they need to be viewed as experimental. It is impossible to obtain the effect of mechanical wave transmission to the inner ear using all 5 physiological ways of BC (mentioned in the Introduction) in cadaver studies [Stenfelt, 2016;Stenfelt and Goode, 2005b]. In our study, a simulation of BC conditions was performed with the device anchored in the bone in a conventional site and 2 experimental sites.…”

Electrophysiological Measurements of Peripheral Vestibular Function—A Review of Electrovestibulography

“…Additionally, the skull is segmented and separated by sutures, and has complex resonance features (Håkansson et al, 1994). Various attempts have been made to model and measure the properties of vibration transmission through the head, primarily in humans, and primarily aimed at understanding BCV hearing (Stenfelt, 2015, 2016). For the human head at least, the skull approximately moves as a rigid structure for BCV below 400 Hz (Stenfelt and Goode, 2005), as a resonant structure between 400 Hz to 2 kHz (Håkansson et al, 1994), and as a wave-propagating structure above 2 kHz (Stenfelt, 2015).…”

“…That is, BCV stimuli can induce neural responses from all vestibular end-organs, despite primarily activating otolithic irregular afferent neurons (Curthoys et al, 2006). Whilst researchers have attempted to use the direction of the applied BCV to activate selected vestibular HCs, it is unlikely that this circumvents the complex 3-dimensional vibration of the inner ear and the complex transduction pathways (Stenfelt, 2015, 2016; Chhan et al, 2016). Mechanical engineers are well aware of the complexity of interpreting the vibrational response of a structure via its “impulse response”.…”