Bone Conduction Devices Research Articles

Assessment of More Than 1,000 Implanted Percutaneous Bone Conduction Devices

This study assesses soft tissue reactions and implant stability of 1,132 percutaneous titanium implants (970 patients) for bone conduction devices (BCDs). In addition, it examines BCD usage and comparisons between different patient groups. Retrospective survey. Mean follow-up time of 4.6 years. Tertiary care referral center. The surveyed cohort was divided into 3 different age groups (children, adults, and the elderly). In addition, 4 groups with variable loading times (i.e., the time between placement of the implant and loading the BCD sound processor) were identified as well as a subgroup of patients with mental retardation. Soft tissue reactions around the percutaneous implants as classified by the Holgers grading system, implant failure, and revision surgery rates. In 95.5% of the 7,415 observations of 1,132 implants, there were no adverse soft tissue reactions. Implant loss was 8.3%. Significantly more soft tissue reactions and implant failures were observed in children compared with adults and the elderly (p < 0.05). Implant survival was lower in patients with mental retardation compared with patients without mental retardation (p = 0.001). The loading time did not influence the occurrence of soft tissue reactions and implant survival rates. Children and patients with mental retardation are the most vulnerable to soft tissue reactions and implant losses. Additional and more frequent care needs to be given during outpatient consultations. Because loading as early as 3 to 5 weeks did not negatively affect skin reactions or implant survival, full BCD installation can occur earlier without risk.

Long-Term Safety and Benefit of a New Intraoral Device for Single-Sided Deafness

To determine the long-term safety and benefit of a new intraoral bone conduction device (SoundBite Hearing System by Sonitus Medical) for single-sided deafness (SSD). A multi-center, controlled, nonrandomized, prospective unblinded study of SSD patients wearing the device over a 6-month period. Ambulatory care centers typical of those where SSD patients are diagnosed and treated. Adults (N = 22) with acquired, permanent SSD and no current use of any other SSD device. Continual daily wear of the new device for 6 months. Comprehensive medical, audiologic, and dental measures; aided thresholds; Abbreviated Profile of Hearing Aid Benefit scores, and an SSD questionnaire. There were no related adverse events or changes in the medical or audiologic findings at the end of the trial compared with the beginning. There were no significant changes in the mean aided thresholds (p > 0.01) or the mean dental measures (p > 0.05) at 3 or 6 months compared with pretrial measures. The mean Abbreviated Profile of Hearing Aid Benefit benefit scores showed improvement (p < 0.01) for the Background Noise, Reverberation, and Ease of Communication subscales and the Global scale at 3 and 6 months. The results of the SSD questionnaire indicated that the vast majority (>90%) of the subjects reported satisfaction and improvement in a variety of areas after wearing the device long term. The SoundBite system is safe and continues to provide substantial benefit for SSD patients with continual daily use over a 6-month period.

Fitting of an 8.5-Millimeter Abutment for Bone Conduction Devices: Indications and Postintervention Course

We present indications and clinical outcomes of fitting an 8.5-mm abutment for bone conduction devices. In 39 cases with a follow-up time of more than 12 months after fitting of an 8.5-mm abutment, the preintervention and postintervention courses were retrospectively evaluated. The outcome measures were indications for fitting and complications during the preintervention and postintervention courses (local skin reaction, skin level, revision surgery, and implant loss). Soft tissue overgrowth was the most frequent reason (31 of 39 cases) for fitting the 8.5-mm abutment. Severe skin reactions decreased by 7.9% after fitting, and the number of fixtures that remained free of any skin reaction increased by 32.2%. In 7 cases, soft tissue overgrowth required revision surgery before placement of the 8.5-mm abutment; further surgical intervention was needed only once. In 1 case, the 8.5-mm abutment was removed because of recurring soft tissue problems. No spontaneous abutment or implant loss occurred. This retrospective evaluation showed that fitting an 8.5-mm abutment is an easy step in managing soft tissue problems and preventing revision surgery. Also, it is of value in patients with a thick scalp that interferes with bone conduction device coupling. In these cases, we advise placing the 8.5-mm abutment during primary surgery.

Efficacy and Safety of an In-the-Mouth Bone Conduction Device for Single-Sided Deafness

To determine the efficacy, benefit, and safety of a new in-the-mouth bone conduction device (SoundBite Hearing System) for single-sided deafness (SSD). A multicenter, controlled, nonrandomized prospective unblinded study of SSD patients wearing the device. Ambulatory care centers typical of those where SSD patients are diagnosed and treated. Adults (ages >18 and <80 yr) with acquired, permanent SSD (N=28) and no current use of any SSD device. Continual daily wear of the new device over a 30-day trial period. The Hearing in Noise Test (HINT), the Abbreviated Profile of Hearing Aid Benefit (APHAB), comprehensive pretrial and posttrial medical, audiologic, and dental examinations and an SSD questionnaire. The Hearing in Noise Test scores improved an average of -2.5 dB after 30 days, compared with wearing no device (p<0.001). The Abbreviated Profile of Hearing Aid Benefit scores improved (p<0.05) for all subjects for the Global and Background Noise subscales and for all but 1 subject for the Reverberation and Ease of Communication subscales. There were no medical, audiologic, or dental complications. The SoundBite system is safe and effective and provides substantial benefit for SSD patients with continual daily use over a 30-day period.

It’s time we listened to our teeth: The SoundBite hearing system

The SoundBite hearing system (Sonitus Medical, San Mateo, Calif) allows people with single-sided deafness to wear an intraoral device and a small microphone in the deaf ear to regain lost hearing. A piezoelectric activator in a small removable unilateral oral appliance conducts sound through the bone via the teeth to the good ear. The goal of this article is to introduce the SoundBite, a new bone-conduction hearing device, to dentists and orthodontists.

A free‐field method to calibrate bone conduction devices.

Bone conduction can be valuable for communication applications and can transmit speech reliably whether or not hearing protection is worn. Audiometric standards for bone conduction vibrators focus primarily on a single model of bone vibrator placed at certain locations on the skull. However, a variety of other models and skull locations may be used for communication, so more general calibration methods are needed. Here we developed a method to calibrate bone vibrators, analogous to free‐field methods of air conduction earphone calibration. Participants were seated in an anechoic chamber with a concealed loudspeaker and were fitted with a bone vibrator headset. Participants adjusted bone vibrator voltage output to perceptually match the loudness of third‐octave noise bands played alternately from the bone vibrator and from the loudspeaker. The judgments were made by six participants, each using two different vibrator models and two different skull locations. Data were analyzed and compared to the data obtained using an artificial mastoid. Discussion will focus on how device types, skull locations, and individual variability affect response curves and comparison to the artificial mastoid and on the feasibility of using the described method as a general method for calibrating and assessing vibrator sensitivity. [Work supported by ORAU.]

Improved Horizontal Directional Hearing in Bone Conduction Device Users with Acquired Unilateral Conductive Hearing Loss

We examined horizontal directional hearing in patients with acquired severe unilateral conductive hearing loss (UCHL). All patients (n = 12) had been fitted with a bone conduction device (BCD) to restore bilateral hearing. The patients were tested in the unaided (monaural) and aided (binaural) hearing condition. Five listeners without hearing loss were tested as a control group while listening with a monaural plug and earmuff, or with both ears (binaural). We randomly varied stimulus presentation levels to assess whether listeners relied on the acoustic head-shadow effect (HSE) for horizontal (azimuth) localization. Moreover, to prevent sound localization on the basis of monaural spectral shape cues from head and pinna, subjects were exposed to narrow band (1/3 octave) noises. We demonstrate that the BCD significantly improved sound localization in 8/12 of the UCHL patients. Interestingly, under monaural hearing (BCD off), we observed fairly good unaided azimuth localization performance in 4/12 of the patients. Our multiple regression analysis shows that all patients relied on the ambiguous HSE for localization. In contrast, acutely plugged control listeners did not employ the HSE. Our data confirm and further extend results of recent studies on the use of sound localization cues in chronic and acute monaural listening.

Preliminary Evaluation of a Novel Bone-Conduction Device for Single-Sided Deafness

A new intraoral bone-conduction device has advantages over existing bone-conduction devices for reducing the auditory deficits associated with single-sided deafness (SSD). Existing bone-conduction devices effectively mitigate auditory deficits from single-sided deafness but have suboptimal microphone locations, limited frequency range, and/or require invasive surgery. A new device has been designed to improve microphone placement (in the ear canal of the deaf ear), provide a wider frequency range, and eliminate surgery by delivering bone-conduction signals to the teeth via a removable oral appliance. Forces applied by the oral appliance were compared with forces typically experienced by the teeth from normal functions such as mastication or from other appliances. Tooth surface changes were measured on extracted teeth, and transducer temperature was measured under typical use conditions. Dynamic operating range, including gain, bandwidth, and maximum output limits, were determined from uncomfortable loudness levels and vibrotactile thresholds, and speech recognition scores were measured using normal-hearing subjects. Auditory performance in noise (Hearing in Noise Test) was measured in a limited sample of SSD subjects. Overall comfort, ease of insertion, and removal and visibility of the oral appliance in comparison with traditional hearing aids were measured using a rating scale. The oral appliance produces forces that are far below those experienced by the teeth from normal functions or conventional dental appliances. The bone-conduction signal level can be adjusted to prevent tactile perception yet provide sufficient gain and output at frequencies from 250 to 12,000 Hz. The device does not damage tooth surfaces nor produce heat, can be inserted and removed easily, and is as comfortable to wear as traditional hearing aids. The new microphone location has advantages for reducing the auditory deficits caused by SSD, including the potential to provide spatial cues introduced by reflections from the pinna, compared with microphone locations for existing devices. A new approach for SSD has been proposed that optimizes microphone location and delivers sound by bone conduction through a removable oral appliance. Measures in the laboratory using normal-hearing subjects indicate that the device provides useful gain and output for SSD patients, is comfortable, does not seem to have detrimental effects on oral function or oral health, and has several advantages over existing devices. Specifically, microphone placement is optimized for reducing the auditory deficit caused by SSD, frequency bandwidth is much greater, and the system does not require surgical placement. Auditory performance in a small sample of SSD subjects indicated a substantial advantage compared with not wearing the device. Future studies will involve performance measures on SSD patients wearing the device for longer periods.

Comparison of Traditional Bone-Conduction Hearing Aids with the Baha® System

Little research exists to demonstrate efficacy and verification measures of the Baha system versus traditional bone-conduction hearing aids. This study gives statistical data about 10 children who have used traditional bone-conduction hearing aids, Baha coupled to a Softband, and the Baha system implanted. The purpose of this study was to compare functional gain at 500, 1000, 2000, and 4000 Hz for infants and children with bilateral conductive hearing loss who were initially fit with traditional bone-conduction devices then progressed to Baha with Softband and finally to unilateral Baha implants. Retrospective five-year chart review. 10 children with bilateral conductive hearing loss due to congenital atresia and/or microtia. Participants ranged in age from 6 mo to 16 yr; three were male and seven were female. Two participants were African-American, five Caucasian, and three Hispanic. The intervention was the Baha system used in children via a Softband or implanted as compared to traditional bone-conduction hearing aids. Single-factor, repeated analyses of variance were run to examine the amount of functional gain delivered by the various devices as well as the threshold measures with each device at each frequency. Participants in this study showed a statistically significant improvement when using the Baha Softband over traditional bone-conduction hearing aids. An implanted Baha has statistically as much gain as a bone-conduction transducer at all frequencies tested. The Baha system is a valid treatment in conductive hearing loss via a Softband or implanted. It statistically outperforms the traditional bone-conduction hearing aids and should be used as a first choice in intervention rather than a last option for inoperable conductive hearing loss.

New Bone-Anchored Amplification Options for Children

New Bone-Anchored Amplification Options for Children

Using the Callsign Acquisition Test (CAT) to investigate the impact of background noise, gender, and bone vibrator location on the intelligibility of bone-conducted speech

Traditionally, combat operations have relied on air-conducted radio communication to receive and transmit information. Recently, however, there has been the need to find alternatives because headphones used in air conduction are bulky and cover the ears of the listener, thus reducing the listener's awareness of his/her surroundings. Bone-conducted radio communication, however, uses lightweight and inconspicuous transducers which allow radio communication without compromising the listener's awareness of his/her surroundings. This research investigated the intelligibility of bone-conducted speech in white, pink, babble and quiet background environments at the condyle and mastoid locations on the head using the Callsign Acquisition Test (CAT). Data were collected and analyzed from 20 normal hearing participants (10 males and 10 females) between the ages of 19 and 31 years. Significant interaction effect between gender and background noise was found from the results. Post-hoc analysis showed that for both males and females, background noise had a significant impact on speech intelligibility. In babble background, there was a significant difference in speech intelligibility between the male and female listeners (males performed better than females). However, no significant effects were found for the other type of background noises. The results also indicated that there was no statistically significant difference in intelligibility scores between the condyle and mastoid locations. Relevance to industry This study investigated the impact of background noise, gender of listener, and location of bone vibrator on the intelligibility of bone-conducted speech. Findings of this study revealed the impact of different background environments and listener's gender on speech intelligibility and will assist in the development of improved bone conduction devices in the future.

Speech intelligibility differences of male and female vocal signals transmitted through bone conduction in background noise: Implications for voice communication headset design

Abstract Tactical organizations require verbal communication that is clear and intelligible. When designing new devices, communication equipment developers must not only consider the electrical components of the devices but also various parameters of both the listening environment and signals being transmitted. Bone conduction communication devices have recently been introduced into several tactical organizations; however, the effectiveness of these devices has not been comprehensively explored. This paper describes a study investigating the impact of voice type (male and female), location (condyle and mastoid), and background noise level (0, 83, 93, and 103 dB(A)) on the intelligibility of bone-conducted verbal communication. Results of the study indicated the male voice tested outperformed the female voice within each noise level except for the 0 dB(A) noise level. At the 0 dB(A) noise level, the female voice outperformed the male voice. There were no performance differences found between locations at the 0 or 83 dB(A) noise levels; however, at the 93 and 103 dB(A) noise levels the condyle outperformed the mastoid. Relevance to industry Various agencies are currently utilizing bone conduction communication devices in tactical missions. Due to the critical nature of these missions, it is important to determine conditions in which bone conduction communication devices are most (and least) effective in order to enhance present and future designs.

The Bone-Anchored Hearing Aid for children: Recent developments

In 1984 the Bone-Anchored Hearing Aid, or BAHA, system was introduced. Its transducer is coupled directly to the skull percutaneously to form a highly effective bone-conduction hearing device. Clinical studies on adults with conductive hearing loss have shown that the BAHA system outperforms conventional bone-conduction hearing aids. Therefore, the next step was to apply the BAHA system in children with congenital or acquired conductive hearing loss. Reviewed data showed that, on average, such children benefited significantly more from the BAHA than from reconstructive surgery. Thus, BAHA application appears to be the best option to achieve normal communication and speech and language development in children with bilateral conductive hearing loss. However, in children under the age of three to four years, a conventional solution must be applied, e.g. a bone conductor with a transcutaneous coupling, because they are too young to undergo BAHA implant surgery. In the case of unilateral congenital conductive hearing loss, there is no convincing evidence in the clinical literature for early intervention.In summary, the BAHA system can be considered a new, indispensable tool for children with bilateral conductive hearing loss.

Using the Callsign Acquisition Test (CAT) to compare the speech intelligibility of air versus bone conduction

In combat operations, the success of most missions relies on the ability of the personnel to interpret speech over a communication system. Thus, the need for effective and efficient communication systems has become increasingly important. Generally, there are two means by which radio communication can be transmitted: air conduction and bone conduction. Although air conduction is more commonly used in industry, bone conducted radio communication offers an attractive means for infantry to communicate on the battlefield. This research used 12 listeners to compare speech intelligibility of bone conduction to that of air conduction in multi-talker noise using signal-to-noise (SN) ratios of −6, −9, and −12 dB. The results showed that in the environments tested, air conduction performed better than bone conduction. It was also found that participants’ performance under the three different SN ratios were significantly different with the best performance under the −6 dB SN ratio. Findings from this research will be helpful for designing communication interfaces for military applications in the future. Relevance to industry This research compares intelligibility of bone- and air-conducted speech using the military's Callsign Acquisition Test (CAT) under different SN ratio conditions. Results from this study will help in the design of better bone conduction devices for the military.

Canal atresia: “Surgery or implantable hearing devices? The expert's question is revisited”

(1) Evaluate hearing results in patients managed with external auditory canal reconstruction; (2) compare results to the expectations from treatment with surgical; placement of an osteo-integrated bone-conduction device (BAHA system); (3) assess complications of both interventions; (4) evaluate the medical cost-effectiveness of each avenue of management at 2005 rates for billings based upon relative value units (RVUs). (1) Retrospective chart review for 36 ears in 29 pediatric patients who underwent surgical canal reconstruction at a tertiary-care pediatric hospital in a major urban center with assessment of management techniques and surgical and audiologic outcomes. (2) Retrospective chart review of six pediatric patients who underwent BAHA placement in a major urban center with assessment of management techniques and surgical and audiologic outcomes. (3) Cost reassessment at 2005 billings rates based upon RVUs for canal reconstruction versus BAHA system and comparative analysis. (1) The average post-operative hearing loss in the right ear was 34.3 dB left ear was 31.6 dB. The average gain per ear was 17.3 dB. (2) Twenty-seven (93%) of EAC reconstruction patients required some form of amplification post-operatively. (3) Data available for three of the BAHA patients reflected the predicted average gain in dB (predicted 34.3 dB, observed 31.8 dB). (4) Early complications of canal reconstruction included removal of the packing by the patient, post-operative bleeding and post-operative hematoma. (5) Late complications included recurrent canal stenosis, recurrent otitis externa, canal prolapse and canal cholesteatoma. (6) Uncomplicated external auditory canal reconstruction cost $51,505.98 or $2909.94/dB of hearing gain based upon billings fro RVUs. (7) Uncomplicated two-staged BAHA system placement cost $42,448.85 or $1237.57/dB of hearing gain based upon billings for RVUs. (8) Uncomplicated single-staged BAHA system placement cost $28,341.00 or $826.27/dB of hearing gain based upon billings for RVUs. Study results indicate that even with significant investments in EAC reconstruction, most patients still required some form of amplification. There are also significant risks of early and late complications from the reconstructive procedure. Studies indicate and our results support that the osteo-integrated bone-conduction device (BAHA system) can achieve truly acceptable hearing (<or=15 dB) in school-aged children with normal bone curves, and it can match the bone-curves for children with sensorineural hearing loss. The two-staged BAHA system placement may be provided at almost one-third the cost to the medical system, on a decibel-for-decibel basis. The single-stage BAHA system placement yields even greater cost savings at just over one-quarter of the cost of surgical EAC reconstruction on a decibel-for-decibel basis. Additionally, there are fewer complications and fewer follow-up visits for the care of the implant system. This is an added value to the parents and patient for the savings in opportunity costs related to the lost time at work and school for office visits and peri-operative care. Overall, it appears that osteo-integrated bone-conduction devices may provide a higher quality of outcome for patients while resulting in significant economic savings.

A study of bone conduction and its applications for audio signal transmission

Human can perceive a sound in two different ways: one is sound transmission through the ear canal, another is that through the skull. The bone conduction technology has been used mainly for hearing impaired listeners and as communication tools in the military organization. Recently, because of a rapid improvement of the bone conduction device, its technology has spread in the field of audio. However, the relationship between the physical characteristic and the subjective responses of bone conduction are not clearly understood. For example, the effect of attachment position and excitation force of bone conduction loudspeakers has been still under discussion. In addition, since the bone conduction units also generate the airborne sound, listeners can hear the sound composed of both the bone conduction sound and the airborne sound. In our previous work, by using of a loudness curve and a threshold of hearing, a fundamental performance of the bone conduction was discussed. In this paper, further investigation will be carried out in order to establish a transmission system of the bone conduction, and the airborne sound on the eardrum that is caused by the vibration of the bone conduction loudspeaker will be measured.

Comparison of Speech Intelligibility Test between Air Conduction and Bone Conduction Using the Callsign Acquisition Test

Communication in the battleground is very critical for the military. With U.S forces engaged in combat operations around the world in the war on terror, the need for effective and efficient communication systems has become more and more important. There are, in general, two types of communication: air conduction and bone conduction. Although air conduction is more commonly used in industry, bone conducted radio communication offers an attractive means for infantry to communicate in the battlefield because it allows radio communication to be transmitted and received without compromising the soldier's awareness of his or her surroundings. Bone conduction interfaces are also lightweight and less bulky and are therefore easy to integrate into military headgear. Based on the findings of previous study, condyle was chosen as the location for the bone vibrator placement. This research compares performance between bone conduction and air conduction using the military's Callsign Acquisition Test (CAT). Results from this study will help better design bone conduction devices for the military in the future.

Output Vibration Measurements of Bone-Anchored Hearing Aids

Hypothesis: Different bone-anchored hearing aids (BAHAs) processors have different output vibration characteristics, which depend on the mechanical load and the volume setting. Responses will differ between live heads and dry or plastic skulls. Background: The BAHA is an implantable bone-conduction device. Three different BAHA models are available. Their output vibrations have not been reported using a noncontact method with differing impedance loads, including the BAHA-fitted patient head. Methods: Using a laser-Doppler vibrometer, vibration responses with sound input of 70- to 80-dB sound pressure level were measured on unloaded BAHAs, a dry skull, a plastic skull, and on the abutments of three live BAHA-fitted patients. Responses at different volume settings and distances from the vibrator were also tested. Frequency responses were calculated for displacement, velocity, and acceleration. Results: Unloaded BAHA accelerations were approximately 30 to 50 dB higher than live-head accelerations. Live-head accelerations were similar to dry skulls in frequencies of more than 500 Hz, but much higher than the plastic skull responses. Live-head responses were more damped. The Cordelle II outperformed the other two processors by approximately 20 dB. The Classic 300 had better low-frequency responses than the Compact. The volume settings had little effect on vibration output overall. Acceleration peak was at approximately 2.5 kHz for all conditions. Conclusion: The BAHA processors differ in the output acceleration they can achieve with differing loads. The volume control setting has little impact on accelerations produced for most processors. The live-head responses are similar to the dry skull in frequencies of more than 500 Hz.

Output Vibration Measurements of Bone-Anchored Hearing Aids

Different bone-anchored hearing aids (BAHAs) processors have different output vibration characteristics, which depend on the mechanical load and the volume setting. Responses will differ between live heads and dry or plastic skulls. The BAHA is an implantable bone-conduction device. Three different BAHA models are available. Their output vibrations have not been reported using a noncontact method with differing impedance loads, including the BAHA-fitted patient head. Using a laser-Doppler vibrometer, vibration responses with sound input of 70- to 80-dB sound pressure level were measured on unloaded BAHAs, a dry skull, a plastic skull, and on the abutments of three live BAHA-fitted patients. Responses at different volume settings and distances from the vibrator were also tested. Frequency responses were calculated for displacement, velocity, and acceleration. Unloaded BAHA accelerations were approximately 30 to 50 dB higher than live-head accelerations. Live-head accelerations were similar to dry skulls in frequencies of more than 500 Hz, but much higher than the plastic skull responses. Live-head responses were more damped. The Cordelle II outperformed the other two processors by approximately 20 dB. The Classic 300 had better low-frequency responses than the Compact. The volume settings had little effect on vibration output overall. Acceleration peak was at approximately 2.5 kHz for all conditions. The BAHA processors differ in the output acceleration they can achieve with differing loads. The volume control setting has little impact on accelerations produced for most processors. The live-head responses are similar to the dry skull in frequencies of more than 500 Hz.

Spatial audio through a bone conduction interface

Headphones are the standard presentation device for radio communication in the military. Although bone conduction devices possess several advantages over headphones for some military applications, they are generally considered inappropriate for inclusion in a multi-channel system. The current study tested the feasibility of a multi-channel bone conduction system by measuring the localizability of spatialized auditory stimuli presented through a pair of bone conduction vibrators. Listeners localized a Gaussian noise stimulus spatialized with individualized head-related transfer functions (HRTFs). The sounds were presented from eight virtual locations on the horizontal plane (0, ±45, ±90, ±135, and 180°) through either stereo headphones or a stereo bone conduction system. Localization performance was found to be nearly identical for both audio systems, indicating that bone conduction systems can be effectively used for displaying spatial information.