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The development of a whole-head human finite-element model for simulation of the transmission of bone-conducted sound
Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences.
Incheon National University, South Korea.
Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences.ORCID iD: 0000-0003-3350-8997
2016 (English)In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 140, no 3, p. 1635-1651Article in journal (Refereed) Published
Abstract [en]

A whole head finite element model for simulation of bone conducted (BC) sound transmission was developed. The geometry and structures were identified from cryosectional images of a female human head and eight different components were included in the model: cerebrospinal fluid, brain, three layers of bone, soft tissue, eye, and cartilage. The skull bone was modeled as a sandwich structure with an inner and outer layer of cortical bone and soft spongy bone (diploe) in between. The behavior of the finite element model was validated against experimental data of mechanical point impedance, vibration of the cochlear promontories, and transcranial BC sound transmission. The experimental data were obtained in both cadaver heads and live humans. The simulations showed multiple low-frequency resonances where the first was caused by rotation of the head and the second was close in frequency to average resonances obtained in cadaver heads. At higher frequencies, the simulation results of the impedance were within one standard deviation of the average experimental data. The acceleration response at the cochlear promontory was overall lower for the simulations compared with experiments but the overall tendencies were similar. Even if the current model cannot predict results in a specific individual, it can be used for understanding the characteristic of BC sound transmission in general. (C) 2016 Acoustical Society of America.

Place, publisher, year, edition, pages
ACOUSTICAL SOC AMER AMER INST PHYSICS , 2016. Vol. 140, no 3, p. 1635-1651
National Category
Vehicle Engineering
Identifiers
URN: urn:nbn:se:liu:diva-133011DOI: 10.1121/1.4962443ISI: 000386932500026PubMedID: 27914383OAI: oai:DiVA.org:liu-133011DiVA, id: diva2:1054671
Note

Funding Agencies|European Union [600933]; Incheon Nation University (International Cooperative) Research Grant

Available from: 2016-12-08 Created: 2016-12-07 Last updated: 2018-03-20
In thesis
1. A Finite Element Model of the Human Head for Simulation of Bone-conducted Sound
Open this publication in new window or tab >>A Finite Element Model of the Human Head for Simulation of Bone-conducted Sound
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Bone conduction is usually understood as the hearing sensation based on the vibrations of the skull bone and surrounding tissues. The fact that vibration of the skull bones can result in a sound percept has been known for a long time. However, it is difficult to give a general definition of BC sound. Normally, BC sound is described as the sound energy transmitted through the body (comprising the solid and fluid parts) then the outer, middle and inner ear are involved and finally produce a perception of sound.

Even if BC sound perception has been studied for more than a century, the whole pattern of BC sound transmission is still not complete. There are limitations for experimental investigation of BC sound, such as the complexity of experimental manipulations and individual differences between subjects resulting in difficult to interpret outcomes. One way to overcome some of those issues is the use of a simulation model for BC sound. However, until now, the published models are unable to provide a holistic response of BC sound in the human. Therefore, the primary aim of this thesis is to develop a finite element model that could simulate BC sound transmission in the human. Based on cryosectional images of a female, the LiUHead was developed as a FE model of the human head with the structure and material properties of real human. Most the structures and tissues which could contribute to the BC transmission were included in the LiUHead. The simulation results of the LiUHead agreed with experimental data obtained in both cadaver heads and live humans.

After the development and validation of the LiUHead, the model was used to investigate BC sound.  Since BC sound is transmitted in and between the tissues, the power transmission of BC sound was investigated in the LiUHead in the frequency domain. When the stimulation was applied on the surface of the skull at the mastoid position, the results of the simulations show that, as the name suggest, the skull bone dominants the BC sound transmission. The soft tissues and cartilages are as the second most important media of the BC sound while the skull interior is the least important for the BC transmission. Moreover, according to the power flux in the skull, the BC vibrations are mainly concentrated at the skull base. Other important transmission pathways are located at the occipital bone at the posterior side of the head, but the power transmitted over the face, forehead and vertex is minor. There is power interaction between the skull bone and skull interior near the stimulation position but the transmission of sound power through the brain seem to be minimal. Since the power or energy is difficult to measure in an experimental setting, this investigation gave unique knowledge about BC sound transmission in the head and the interaction between the tissues.

As a common application for BC sound, bone-conduction devices are used to stimulate the hearing and is a method for hearing loss rehabilitation. Nowadays many different kinds of BCDs are available. However, most studies failed to compare the different types of BCDs in the same conditions as well as between several BCDs as it is not possible to compare several BCDs within the same subject due to the implantation required for several BCDs. The model gives a unique opportunity to evaluate various BCDs in the same head. Eight different BCDs, including four kinds of skin-drive BCDs, three kinds of direct-drive BCDs, and one in-the-mouth device, were applied to the LiUHead and the simulation results were evaluated. The results proved that the direct-drive BCDs and the in-the-mouth device gave similar vibration responses at the cochlea. At low frequencies, the skin-drive BCDs had similar or even better cochlear responses than the direct-drive BCDs. However, the direct-drive BCDs gave stable responses at mid-frequencies and gave higher responses than the skin-drive BCDs at high frequencies. These results are beneficial evaluating and for designing and improving current BCDs.

The ultimate goal of this thesis is to provide a computational model for BC sound that can be used for evaluation of BC sound transmission. This was accomplished by the LiUHead that gave results comparable to experimental data and enabled investigations that cannot easily be conducted in experiments.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2018. p. 40
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1622
Keywords
bone conduction, finite element model,bone-conduction devices
National Category
Other Medical Sciences
Identifiers
urn:nbn:se:liu:diva-145666 (URN)10.3384/diss-diva.145666 (DOI)9789176853108 (ISBN)
Public defence
2018-04-27, Belladonna, Entrance 78, Campus US, Linköping, 09:00 (English)
Opponent
Supervisors
Available from: 2018-04-03 Created: 2018-03-20 Last updated: 2018-04-09Bibliographically approved

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