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

You Chang,Stefan Stenfelt,Namkeun Kim

doi:10.1007/s10237-018-1053-4

Abstract

Bone conduction (BC) sound is the perception of sound transmitted in the skull bones and surrounding tissues. To better understand BC sound perception and the interaction with surrounding tissues, the power transmission of BC sound is investigated in a three-dimensional finite-element model of a whole human head. BC sound transmission was simulated in the FE model and the power dissipation as well as the power flow following a mechanical vibration at the mastoid process behind the ear was analyzed. The results of the simulations show that the skull bone (comprises the cortical bone and diploë) has the highest BC power flow and thereby provide most power transmission for BC sound. The soft tissues was the second most important media for BC sound power transmission, while the least BC power transmission is through the brain and the surrounding cerebrospinal fluid (CSF) inside the cranial vault. The vibrations transmitted in the skull are mainly concentrated at the skull base when the stimulation is at the mastoid. Other vibration transmission pathways of importance are located at the occipital bone at the posterior side of the head while the transmission of sound power through the face, forehead and vertex is minor. The power flow between the skull bone and skull interior indicate that some BC power is transmitted to and from the skull interior but the transmission of sound power through the brain seem to be minimal and only local to the brain–bone interface.

Highlights

Bone-conducted (BC) sound produces an auditory sensation when vibrations stimulate the inner ear via mechanisms different from ordinary air conduction (AC) transmission through the ear canal and middle ear (Stenfelt and Goode 2005b)
The BC powers dissipated in the three structures of the head are shown in Fig. 3 where the power in the soft tissue and cartilages is shown with a solid line, in the skull bone with a dashed line, and in the brain with a dotted line
The dissipated power decreases with frequency at the lowest frequencies for all structures but increases above 150 Hz for the skull bone and soft tissues while it is relatively constant for the skull interior

Summary

Introduction

Bone-conducted (BC) sound produces an auditory sensation when vibrations stimulate the inner ear via mechanisms different from ordinary air conduction (AC) transmission through the ear canal and middle ear (Stenfelt and Goode 2005b). The main distinction between AC and BC sound is that BC sound has a dominant sound power transmission through the skull bone (Eeg-Olofsson et al 2008; Stenfelt and Goode 2005a; Eeg-Olofsson et al 2013), the soft tissues, or the interior of the skull (Sim et al 2016; Roosli et al 2016). Hearing by BC is usually described as sound power transmitted through the body (Stenfelt 2013). An investigation of the sound power transmission could result in a better understanding of BC hearing in the human. One possible solution is to compute the power transmission using a simulation model for BC sound

Methods

Results

Discussion

Conclusion