Sabine Reinfeldt

A model of the occlusion effect with bone-conducted stimulation

An acoustical model using simplified ear anatomy was designed to predict the ear-canal sound pressure occlusion effect in humans. These predictions were compared perceptually as well as with ear-canal sound pressure occlusion effect measurements using a foam earplug with shallow insertion, a foam earplug with deep insertion into the bony part of the ear canal, and a circumaural earmuff. There was good resemblance between model predictions and ear-canal sound pressure measurements. It was also found that all occlusion positions, even deep ear-canal occlusion, produced noticeable occlusion effects. With the bone-conduction transducer at the forehead, the perceived occlusion effect was close to that obtained from ear-canal sound pressure data in the 0.3 to 2 kHz frequency range; when the stimulation was at the mastoid the difference between the perceived and measured ear-canal sound pressure occlusion effect was around 10 dB at frequencies below 1 kHz. Further, the occlusion effect was obtained in two clinical settings: with supra-aural earphones (TDH39), and insert earphones (CIR22). Although both transducers produced occlusion effects, insert earphones produced a greater effect than surpa-aural earphones at the low frequencies.

Percutaneous versus transcutaneous bone conduction implant system: a feasibility study on a cadaver head.

Objective: Percutaneous bone-anchored hearing aid (BAHA) is an important rehabilitation alternative for patients who have conductive or mixed hearing loss. However, these devices use a percutaneous and bone-anchored implant that has some drawbacks reported. A transcutaneous bone conduction implant system (BCI) is proposed as an alternative to the percutaneous system because it leaves the skin intact. The BCI transmits the signal to a permanently implanted transducer with an induction loop system through the intact skin. The aim of this study was to compare the electroacoustic performance of the BAHA Classic-300 with a full-scale BCI on a cadaver head in a sound field. The BCI comprised the audio processor of the vibrant sound bridge connected to a balanced vibration transducer (balanced electromagnetic separation transducer). Methods: Implants with snap abutments were placed in the parietal bone (Classic-300) and 15-mm deep in the temporal bone (BCI). The vibration responses at the ipsilateral and contralateral cochlear promontories were measured with a laser Doppler vibrometer, with the beam aimed through the ear canal. Results: Results show that the BCI produces approximately 5 dB higher maximum output level and has a slightly lower distortion than the Classic-300 at the ipsilateral promontorium at speech frequencies. At the contralateral promontorium, the maximum output level was considerably lower for the BCI than for the Classic-300 except in the 1-2 kHz range, where it was similar. Conclusion: Present results support the proposal that a BCI system can be a realistic alternative to a BAHA.

A novel bone conduction implant (BCI): Engineering aspects and pre-clinical studies

Abstract Percutaneous bone anchored hearing aids (BAHA) are today an important rehabilitation alternative for patients suffering from conductive or mixed hearing loss. Despite their success they are associated with drawbacks such as skin infections, accidental or spontaneous loss of the bone implant, and patient refusal for treatment due to stigma. A novel bone conduction implant (BCI) system has been proposed as an alternative to the BAHA system because it leaves the skin intact. Such a BCI system has now been developed and the encapsulated transducer uses a non-screw attachment to a hollow recess of the lateral portion of the temporal bone. The aim of this study is to describe the basic engineering principals and some preclinical results obtained with the new BCI system. Laser Doppler vibrometer measurements on three cadaver heads show that the new BCI system produces 0–10 dB higher maximum output acceleration level at the ipsilateral promontory relative to conventional ear-level BAHA at speech frequencies. At the contralateral promontory the maximum output acceleration level was considerably lower for the BCI than for the BAHA. Sumario Los auxiliares auditivos anclados al hueso (BAHA) en forma percutánea son hoy en día una alternativa importante de rehabilitación para pacientes que sufren de pérdidas auditiva conductivas o mixtas. A pesar de su éxito, ellos se asocian con algunos problemas, tales como infecciones de la piel, pérdida accidental o espontánea del implante óseo, o el rechazo del paciente al tratamiento por razones de estigma. Se ha prop-uesto un novedoso sistema de implante de conducción ósea (BCI) que deja la piel intacta, como una alternativa al sistema BAHA. El sistema de BCI ha sido ya desarrollado y el transductor encapsulado utiliza una unión sin tornillo a un receso hueco en la porción lateral del hueso temporal. El objetivo de este estudio es describir los principios básicos de ingeniería y algunos resultados pre-clínicos obtenidos con el nuevo sistema BCI. Mediciones con un vibrómetro Laser Doppler sobre tres cabezas de cadáver muestran que el nuevo sistema BCI produce un nivel más alto de aceleración máxima de salida de 0–10 dB en el promontorio ipsilateral, en relación con el BAHA convencional a la altura del oído, en las frecuencias del lenguaje. En el promontorio contralateral, el nivel máximo de aceleración de salida fue considerablemente más bajo para el BCI que para el BAHA.

New developments in bone-conduction hearing implants: a review

The different kinds of bone-conduction devices (BCDs) available for hearing rehabilitation are growing. In this paper, all BCDs currently available or in clinical trials will be described in categories according to their principles. BCDs that vibrate the bone via the skin are referred to as skin-drive devices, and are divided into conventional devices, which are attached with softbands, for example, and passive transcutaneous devices, which have implanted magnets. BCDs that directly stimulate the bone are referred to as direct-drive devices, and are further divided into percutaneous and active transcutaneous devices; the latter have implanted transducers directly stimulating the bone under intact skin. The percutaneous direct-drive device is known as a bone-anchored hearing aid, which is the BCD that has the largest part of the market today. Because of some issues associated with the percutaneous implant, and to some extent because of esthetics, more transcutaneous solutions with intact skin are being developed today, both in the skin-drive and in the direct-drive category. Challenges in developing transcutaneous BCDs are mostly to do with power, attachment, invasiveness, and magnetic resonance imaging compatibility. In the future, the authors assume that the existing percutaneous direct-drive BCD will be retained as an important rehabilitation alternative, while the transcutaneous solutions will increase their part of the market, especially for patients with bone-conduction thresholds better than 35 dB HL (hearing level). Furthermore, the active transcutaneous direct-drive BCDs appear to be the most promising systems, but to establish more detailed inclusion criteria, and potential benefits and drawbacks, more extensive clinical studies are needed.

Examination of bone-conducted transmission from sound field excitation measured by thresholds, ear-canal sound pressure, and skull vibrations

Bone conduction (BC) relative to air conduction (AC) sound field sensitivity is here defined as the perceived difference between a sound field transmitted to the ear by BC and by AC. Previous investigations of BC-AC sound field sensitivity have used different estimation methods and report estimates that vary by up to 20 dB at some frequencies. In this study, the BC-AC sound field sensitivity was investigated by hearing threshold shifts, ear canal sound pressure measurements, and skull bone vibrations measured with an accelerometer. The vibration measurement produced valid estimates at 400 Hz and below, the threshold shifts produced valid estimates at 500 Hz and above, while the ear canal sound pressure measurements were found erroneous for estimating the BC-AC sound field sensitivity. The BC-AC sound field sensitivity is proposed, by combining the present result with others, as frequency independent at 50 to 60 dB at frequencies up to 900 Hz. At higher frequencies, it is frequency dependent with minima of 40 to 50 dB at 2 and 8 kHz, and a maximum of 50 to 60 dB at 4 kHz. The BC-AC sound field sensitivity is the theoretical limit of maximum attenuation achievable with ordinary hearing protection devices.

Transmission of bone conducted sound - Correlation between hearing perception and cochlear vibration

The vibration velocity of the lateral semicircular canal and the cochlear promontory was measured on 16 subjects with a unilateral middle ear common cavity, using a laser Doppler vibrometer, when the stimulation was by bone conduction (BC). Four stimulation positions were used: three ipsilateral positions and one contralateral position. Masked BC pure tone thresholds were measured with the stimulation at the same four positions. Valid vibration data were obtained at frequencies between 0.3 and 5.0 kHz. Large intersubject variation of the results was found with both methods. The difference in cochlear velocity with BC stimulation at the four positions varied as a function of frequency while the tone thresholds showed a tendency of lower thresholds with stimulation at positions close to the cochlea. The correlation between the vibration velocities of the two measuring sites of the otic capsule was high. Also, relative median data showed similar trends for both vibration and threshold measurements. However, due to the high variability for both vibration and perceptual data, low correlation between the two methods was found at the individual level. The results from this study indicated that human hearing perception from BC sound can be estimated from the measure of cochlear vibrations of the otic capsule. It also showed that vibration measurements of the cochlea in cadaver heads are similar to that measured in live humans.

Hearing one’s own voice during phoneme vocalization—Transmission by air and bone conduction

The relationship between the bone conduction (BC) part and the air conduction (AC) part of ones own voice has previously not been well determined. This relation is important for hearing impaired subjects as a hearing aid affects these two parts differently and thereby changes the perception of ones own voice. A large ear-muff that minimized the occlusion effect while still attenuating AC sound was designed. During vocalization and wearing the ear muff the ear-canal sound pressure could be related to the BC component of a persons own voice while the AC component was derived from the sound pressure at the entrance of an open ear-canal. The BC relative to AC sensitivity of ones own voice was defined as the ratio between these two components related to the ear-canal sound pressure at hearing thresholds for BC and AC stimulation. The results of ten phonemes showed that the BC part of ones own voice dominated at frequencies between 1 and 2 kHz for most of the phonemes. The different phonemes gave slightly different results caused by differences during vocalization. However, similarities were seen for phonemes with comparable vocalization.

The Bone Conduction Implant-First Implantation, Surgical and Audiologic Aspects.

Objective To report on preoperative assessment, surgery, and audiologic outcome of the first patient implanted with the bone conduction implant (BCI). Background The BCI is a bone conduction hearing device with an intact skin solution where the transducer is implanted close to the ear canal opening. By avoiding a percutaneous screw attachment to the skull, the BCI is anticipated to reduce complications associated with the Bone-Anchored Hearing Aid (BAHA) solution. Methods The first patient to receive a BCI was a 42-year-old woman with a unilateral mixed hearing loss due to tympanosclerosis. Preoperative and postoperative cone beam computed tomography and a virtual planning tool for 3D reconstruction were used to optimize and control the position of the BCI in the mastoid. The transducer was placed in a 5-mm deep seating in the mastoid and secured with a titanium bar. Free field tone and speech audiometry were conducted to evaluate the audiologic outcome at baseline (1 month postoperatively) and 1 month after baseline. Results The BCI was placed in the position according to the preoperative 3D planning. On average, the tone thresholds improved by 30 dB, speech reception thresholds by 25.5 dB and speech signal-to-noise ratio by 9.7 dB. The surgical procedure was considered simple and safe. Conclusion The BCI can be implanted by a safe and easy surgical procedure. 3D preoperative planning can be helpful to optimize the BCI position. The BCI is a realistic alternative to the BAHA.

The bone conduction implant: Clinical results of the first six patients

Abstract Objective: To investigate audiological and quality of life outcomes for a new active transcutaneous device, called the bone conduction implant (BCI), where the transducer is implanted under intact skin. Design: A clinical study with sound field audiometry and questionnaires at six-month follow-up was conducted with a bone-anchored hearing aid on a softband as reference device. Study sample: Six patients (age 18–67 years) with mild-to-moderate conductive or mixed hearing loss. Results: The surgical procedure was found uneventful with no adverse events. The first hypothesis that BCI had a statistically significant improvement over the unaided condition was proven by a pure-tone-average improvement of 31.0 dB, a speech recognition threshold improvement in quiet (27.0 dB), and a speech recognition score improvement in noise (51.2 %). At speech levels, the signal-to-noise ratio threshold for BCI was − 5.5 dB. All BCI results were better than, or similar to the reference device results, and the APHAB and GBI questionnaires scores showed statistically significant improvements versus the unaided situation, supporting the second and third hypotheses. Conclusions: The BCI provides significant hearing rehabilitation for patients with mild-to-moderate conductive or mixed hearing impairments, and can be easily and safely implanted under intact skin.

Bone conduction hearing sensitivity in normal-hearing subjects: Transcutaneous stimulation at BAHA vs BCI position

Abstract Objective: Bone conduction (BC) stimulation closer to the cochlea has previously been shown to give higher cochlear promontory acceleration measured by laser Doppler vibrometry (LDV). This study is investigating whether stimulation closer to the cochlea also gives improved hearing sensitivity. Furthermore, the study compares shifts in hearing sensitivity (BC thresholds) and ear-canal sound pressure (ECSP). Design: BC hearing thresholds and ECSP have been measured for stimulation at two positions: the existing bone-anchored hearing aid (BAHA) position, and a new bone conduction implant (BCI) position that is located closer to the cochlea. Study sample: The measurements were made on 20 normal-hearing subjects. Results: Depending on frequency, the ipsilateral hearing threshold was 3–14 dB better, and the ipsilateral ECSP was 2–12 dB higher for the BCI than for the BAHA position, with no significant differences between threshold and ECSP shifts at group level for most frequencies, and individually only for some subjects. Conclusions: It was found that both the objective ECSP and the subjective hearing threshold measurements gave similar improvement as previous LDV measurements for stimulation closer to the cochlea. One exception was that the LDV measurements did not show the improved sensitivity for frequencies below 500 Hz found here.