| 1. |
- Asp, Filip, et al.
(författare)
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A longitudinal study of the bilateral benefit in children with bilateral cochlear implants
- 2015
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Ingår i: International Journal of Audiology. - : Taylor & Francis. - 1499-2027 .- 1708-8186. ; 54:2, s. 77-88
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To study the development of the bilateral benefit in children using bilateral cochlear implants by measurements of speech recognition and sound localization.DESIGN: Bilateral and unilateral speech recognition in quiet, in multi-source noise, and horizontal sound localization was measured at three occasions during a two-year period, without controlling for age or implant experience. Longitudinal and cross-sectional analyses were performed. Results were compared to cross-sectional data from children with normal hearing.STUDY SAMPLE: Seventy-eight children aged 5.1-11.9 years, with a mean bilateral cochlear implant experience of 3.3 years and a mean age of 7.8 years, at inclusion in the study. Thirty children with normal hearing aged 4.8-9.0 years provided normative data.RESULTS: For children with cochlear implants, bilateral and unilateral speech recognition in quiet was comparable whereas a bilateral benefit for speech recognition in noise and sound localization was found at all three test occasions. Absolute performance was lower than in children with normal hearing. Early bilateral implantation facilitated sound localization.CONCLUSIONS: A bilateral benefit for speech recognition in noise and sound localization continues to exist over time for children with bilateral cochlear implants, but no relative improvement is found after three years of bilateral cochlear implant experience.
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| 2. |
- Bernstein, Joshua G. W., et al.
(författare)
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Spectrotemporal Modulation Sensitivity as a Predictor of Speech-Reception Performance in Noise With Hearing Aids
- 2016
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Ingår i: TRENDS IN HEARING. - : SAGE PUBLICATIONS INC. - 2331-2165. ; 20
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Tidskriftsartikel (refereegranskat)abstract
- The audiogram predicts amp;lt;30% of the variance in speech-reception thresholds (SRTs) for hearing-impaired (HI) listeners fitted with individualized frequency-dependent gain. The remaining variance could reflect suprathreshold distortion in the auditory pathways or nonauditory factors such as cognitive processing. The relationship between a measure of suprathreshold auditory function-spectrotemporal modulation (STM) sensitivity-and SRTs in noise was examined for 154 HI listeners fitted with individualized frequency-specific gain. SRTs were measured for 65-dB SPL sentences presented in speech-weighted noise or four-talker babble to an individually programmed master hearing aid, with the output of an ear-simulating coupler played through insert earphones. Modulation-depth detection thresholds were measured over headphones for STM (2cycles/octave density, 4-Hz rate) applied to an 85-dB SPL, 2-kHz lowpass-filtered pink-noise carrier. SRTs were correlated with both the high-frequency (2-6 kHz) pure-tone average (HFA; R-2 = .31) and STM sensitivity (R-2 = .28). Combined with the HFA, STM sensitivity significantly improved the SRT prediction (Delta R-2 = .13; total R-2 = .44). The remaining unaccounted variance might be attributable to variability in cognitive function and other dimensions of suprathreshold distortion. STM sensitivity was most critical in predicting SRTs for listenersamp;lt;65 years old or with HFA amp;lt;53 dB HL. Results are discussed in the context of previous work suggesting that STM sensitivity for low rates and low-frequency carriers is impaired by a reduced ability to use temporal fine-structure information to detect dynamic spectra. STM detection is a fast test of suprathreshold auditory function for frequencies amp;lt;2 kHz that complements the HFA to predict variability in hearing-aid outcomes for speech perception in noise.
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| 3. |
- Chang, You, 1985-
(författare)
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A Finite Element Model of the Human Head for Simulation of Bone-conducted Sound
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 4. |
- Chang, You, et al.
(författare)
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Characteristics of Bone-Conduction Devices Simulated in a Finite-Element Model of a Whole Human Head
- 2019
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Ingår i: TRENDS IN HEARING. - : SAGE PUBLICATIONS INC. - 2331-2165. ; 23
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Tidskriftsartikel (refereegranskat)abstract
- Nowadays, many different kinds of bone-conduction devices (BCDs) are available for hearing rehabilitation. Most studies of these devices fail to compare the different types of BCDs under the same conditions. Moreover, most results are between two BCDs in the same subject, or two BCDs in different subjects failing to provide an overview of the results between several of the BCDs. Another issue is that some BCDs require surgical procedures that prevent comparison of the BCDs in the same persons. In this study, four types of skin-drive BCDs, three direct-drive BCDs, and one oral device were evaluated in a finite-element model of the human head that was able to simulate all BCDs under the same conditions. The evaluation was conducted using both a dynamic force as input and an electric voltage to a model of a BCD vibrator unit. The results showed that the direct-drive BCDs and the oral device gave vibration responses within 10 dB at the cochlea. The skin-drive BCDs had similar or even better cochlear vibration responses than the direct-drive BCDs at low frequencies, but the direct-drive BCDs gave up to 30 dB higher cochlear vibration responses at high frequencies. The study also investigated the mechanical point impedance at the interface between the BCD and the head, providing information that explains some of the differences seen in the results. For example, when the skin-drive BCD attachment area becomes too small, the transducer cannot provide an output force similar to the devices with larger attachment surfaces.
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| 5. |
- Chang, You, et al.
(författare)
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Simulation of Bone-Conducted Sound Transmission in a Three-Dimensional Finite-Element Model of a Human Skull
- 2015
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Ingår i: MECHANICS OF HEARING: PROTEIN TO PERCEPTION. - : AMER INST PHYSICS. - 9780735413504
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Konferensbidrag (refereegranskat)abstract
- Bone conduction (BC) is the transmission of sound to the inner ear through the bones of the skull. This type of transmission is used in humans fitted with BC hearing aids as well as to classify between conductive and sensorineural hearing losses. The objective of the present study is to develop a finite-element (FE) model of the human skull based on cryosectional images of a female cadaver head in order to gain better understanding of the sound transmission. Further, the BC behavior was validated in terms of sound transmission against experimental data published in the literature. Results showed the responses of the simulated skull FE model were consistent with the experimentally reported data.
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| 6. |
- Chang, You, et al.
(författare)
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Simulation of the power transmission of bone-conducted sound in a finite-element model of the human head
- 2018
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Ingår i: Biomechanics and Modeling in Mechanobiology. - : SPRINGER HEIDELBERG. - 1617-7959 .- 1617-7940. ; 17:6, s. 1741-1755
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Tidskriftsartikel (refereegranskat)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 diploe) 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.
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| 7. |
- Chang, You, et al.
(författare)
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The development of a whole-head human finite-element model for simulation of the transmission of bone-conducted sound
- 2016
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Ingår i: Journal of the Acoustical Society of America. - : ACOUSTICAL SOC AMER AMER INST PHYSICS. - 0001-4966 .- 1520-8524. ; 140:3, s. 1635-1651
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
- Dobrev, Ivo, et al.
(författare)
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Influence of stimulation position on the sensitivity for bone conduction hearing aids without skin penetration
- 2016
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Ingår i: International Journal of Audiology. - : TAYLOR & FRANCIS LTD. - 1499-2027 .- 1708-8186. ; 55:8, s. 439-446
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Tidskriftsartikel (refereegranskat)abstract
- Objective: This study explores the influence of stimulation position on bone conduction (BC) hearing sensitivity with a BC transducer attached using a headband. Design:(1) The cochlear promontory motion was measured in cadaver heads using laser Doppler vibrometry while seven different positions around the pinna were stimulated using a bone anchored hearing aid transducer attached using a headband. (2) The BC hearing thresholds were measured in human subjects, with the bone vibrator Radioear B71 attached to the same seven stimulation positions. Study sample: Three cadaver heads and twenty participants. Results: Stimulation on a position superior-anterior to the pinna generated the largest promontory motion and the lowest BC thresholds. Stimulations on the positions superior to the pinna, the mastoid, and posterior-inferior to the pinna showed similar magnitudes of promontory motion and similar levels of BC thresholds. Conclusion: Stimulations on the regions superior to the pinna, the mastoid, and posterior-inferior to the pinna provide stable BC transmission, and are insensitive to small changes of the stimulation position. Therefore it is reliable to use the mastoid to determine BC thresholds in clinical audiometry. However, stimulation on a position superior-anterior to the pinna provides more efficient BC transmission than stimulation on the mastoid.
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| 9. |
- Dobrev, Ivo, et al.
(författare)
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Sound wave propagation on the human skull surface with bone conduction stimulation
- 2017
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Ingår i: Hearing Research. - : ELSEVIER SCIENCE BV. - 0378-5955 .- 1878-5891. ; 355
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Tidskriftsartikel (refereegranskat)abstract
- Background: Bone conduction (BC) is an alternative to air conduction to stimulate the inner ear. In general, the stimulation for BC occurs on a specific location directly on the skull bone or through the skin covering the skull bone. The stimulation propagates to the ipsilateral and contralateral cochlea, mainly via the skull bone and possibly via other skull contents. This study aims to investigate the wave propagation on the surface of the skull bone during BC stimulation at the forehead and at ipsilateral mastoid. Methods: Measurements were performed in five human cadaveric whole heads. The electro-magnetic transducer from a BCHA (bone conducting hearing aid), a Baha (R) Cordelle II transducer in particular, was attached to a percutaneously implanted screw or positioned with a 5-Newton steel headband at the mastoid and forehead. The Baha transducer was driven directly with single tone signals in the frequency range of 0.25-8 kHz, while skull bone vibrations were measured at multiple points on the skull using a scanning laser Doppler vibrometer (SLDV) system and a 3D LDV system. The 3D velocity components, defined by the 3D LDV measurement coordinate system, have been transformed into tangent (in-plane) and normal (out-of-plane) components in a local intrinsic coordinate system at each measurement point, which is based on the cadaver heads shape, estimated by the spatial locations of all measurement points. Results: Rigid-body-like motion was dominant at low frequencies below 1 kHz, and clear transverse traveling waves were observed at high frequencies above 2 kHz for both measurement systems. The surface waves propagation speeds were approximately 450 m/s at 8 kHz, corresponding trans-cranial time interval of 0.4 ms. The 3D velocity measurements confirmed the complex space and frequency dependent response of the cadaver heads indicated by the ID data from the SLDV system. Comparison between the tangent and normal motion components, extracted by transforming the 3D velocity components into a local coordinate system, indicates that the normal component, with spatially varying phase, is dominant above 2 kHz, consistent with local bending vibration modes and traveling surface waves. Conclusion: Both SLDV and 3D LDV data indicate that sound transmission in the skull bone causes rigid body-like motion at low frequencies whereas transverse deformations and travelling waves were observed above 2 kHz, with propagation speeds of approximately of 450 m/s at 8 kHz. (C) 2017 Elsevier B.V. All rights reserved.
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| 10. |
- Hengen, Johanna, et al.
(författare)
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Perceived Voice Quality and Voice-Related Problems Among Older Adults With Hearing Impairments
- 2018
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Ingår i: Journal of Speech, Language and Hearing Research. - : AMER SPEECH-LANGUAGE-HEARING ASSOC. - 1092-4388 .- 1558-9102. ; 61:9, s. 2168-2178
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Tidskriftsartikel (refereegranskat)abstract
- The auditory system helps regulate phonation. A speakers perception of their own voice is likely to be of both emotional and functional significance. Although many investigations have observed deviating voice qualities in individuals who are prelingually deaf or profoundly hearing impaired, less is known regarding how older adults with acquired hearing impairments perceive their own voice and potential voice problems. Purpose: The purpose of this study was to investigate problems relating to phonation and self-perceived voice sound quality in older adults based on hearing ability and the use of hearing aids. Method: This was a cross-sectional study, with 290 participants divided into 3 groups (matched by age and gender): (a) individuals with hearing impairments who did not use hearing aids (n = 110), (b) individuals with hearing impairments who did use hearing aids (n = 110), and (c) individuals with no hearing impairments (n = 70). All participants underwent a pure-tone audiometry exam; completed standardized questionnaires regarding their hearing, voice, and general health; and were recorded speaking in a soundproof room. Results: The hearing aid users surpassed the benchmarks for having a voice disorder on the Voice Handicap Index (VHI; Jacobson et al., 1997) at almost double the rate predicted by the Swedish normative values for their age range, although there was no significant difference in acoustical measures between any of the groups. Both groups with hearing impairments scored significantly higher on the VHI than the control group, indicating more impairment. It remains inconclusive how much hearing loss versus hearing aids separately contribute to the difference in voice problems. The total scores on the Hearing Handicap Inventory for the Elderly (Ventry amp; Weinstein, 1982), in combination with the variables gender and age, explained 21.9% of the variance on the VHI. Perceiving ones own voice as being distorted, dull, or hollow had a strong negative association with a general satisfaction about the sound quality of ones own voice. In addition, groupwise differences in own-voice descriptions suggest that a negative perception of ones voice could be influenced by alterations caused by hearing aid processing. Conclusions: The results indicate that hearing impairments and hearing aids affect several aspects of vocal satisfaction in older adults. A greater understanding of how hearing impairments and hearing aids relate to voice problems may contribute to better voice and hearing care.
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