Bone Conduction Hearing Device Research Articles

Examining Force Level Output of Skin-Drive Bone Conduction Hearing Devices in Adults With Simulated Conductive Hearing Loss.

Bone conduction hearing devices (BCDs) that deliver sound across the skin (i.e., transcutaneous) are suitable for some individuals who have conductive or mixed hearing losses. Prescriptive targets for percutaneous devices are available, for example, from the Desired Sensation Level-Bone Conduction Hearing Device (DSL-BCD) algorithm. These targets, however, may require modification for use with transcutaneous BCDs. The current study investigated three key variables that may inform target modification: (a) comparison of thresholds measured using an audiometric bone conduction (BC) transducer versus transcutaneous BCDs that offer in situ threshold measurement, (b) transcutaneous BCD default force level outputs versus recommended DSL percutaneous BC targets, and (c) the preferred listening levels (PLLs) of adults wearing transcutaneous BCDs in a laboratory setting. Bilateral conductive hearing loss was simulated in 20 normal-hearing adults via earplugs. Thresholds were measured using a B-71 BC transducer and two commercially available BCDs coupled to a soft headband. DSL percutaneous BC targets were generated, and PLLs were obtained for a 60-dB SPL speech stimulus. Force level outputs were measured using a skull simulator on the Audioscan Verifit2 at the hearing aids' default settings and at the participants' PLL for each device. On average, audiometric BC thresholds were significantly better than those measured in situ with each BCD. PLLs were similar to prescribed targets for one device with the smoother response shape and agreed in the high frequencies for both devices. In situ thresholds are significantly higher than audiometric BC thresholds, suggesting that device-based in situ measurement more accurately accounts for the signal transmission from transcutaneous BCDs. PLLs differed from the percutaneous targets and varied between devices, which may indicate that either target modifications or manipulations of device frequency response shaping are needed to approximate PLL with transcutaneous BCD devices.

Staged implantation of active transcutaneous bone conduction hearing devices (BCHD) after explantation of older generation bone anchored hearing aids (BAHAs): Surgical outcomes and approach to management

PurposeTo evaluate outcomes following explantation of percutaneous or transcutaneous bone conduction implants (pBCIs or tBCIs) and subsequent implantation of transcutaneous active bone conduction hearing devices (BCHDs); to provide guidance regarding staging of surgery and adjunctive procedures. Materials and methodsRetrospective chart review of eight adult subjects (ten ears) with pBCIs or tBCIs who underwent explantation of their device and subsequent implantation with a BCHD [MED-EL BONEBRIDGE™ (n = 7, 70 %) or Cochlear™ Osia® (n = 3, 30 %)]. ResultsReasons for pBCI or tBCI explantation were pain (60 %, 6/10), infection (60 %, 6/10), skin overgrowth (50 %, 5/10), and inability to obtain new processors (20 %, 2/10). Median time between pBCI or tBCI removal and BCHD staged implant was 4.7 (IQR 2.2–8.1) months. Two subjects developed complications following BCHD implantation. One had a persistent wound overlying the osseointegrated screw after removal of the pBCI abutment, requiring removal and temporalis rotational flap. Staged Osia® implantation was performed, but ultimately wound dehiscence developed over the device. The second subject experienced an infection after BONEBRIDGE™ implantation (32 days after pBCI explant), necessitating washout and treatment with intravenous antibiotics. There was subsequent device failure. ConclusionThe transition from a pBCI or tBCI to a novel transcutaneous device is nuanced. Staged pBCI or tBCI explantation and novel BCHD implantation with sufficient time for wound healing is vital. Adjunctive procedures to augment soft tissue in cases of prior attenuation may be required to avoid complications with larger internal devices.

Clinical Outcomes of an Active, Transcutaneous, Bone Conduction Hearing Device: A Retrospective Study.

The purpose of this study was to review patient demographics, indications, intraoperative findings, complications/adverse events, and audiological outcomes related to the implantation of the Osia 2 device. Retrospective case series. Single tertiary institutional experience. Patients who had undergone Osia 2 implantation by the senior author were identified from 2019 to present. Information was extracted from patient charts concerning patient demographics, indications for implantation, surgical findings, audiological outcomes, and adverse events. Sixty patients and 67 implants were included. The median age was 51 years (R: 11-92). Fifty-five percentof patients had mixed hearing loss (HL), 30% had single-sided deafness, and 15% had conductive HL. The mean operative time was 53.9minutes. Only 4.5% of patients required bone polishing, and 3.0% required tissue thinning. Themean pure-tone averages 4 gain from unaided conditions was 41.2 dB. Mean gain at 6and 8 kHz from unaided conditions was 35.42and 40.67 dB, respectively. Mean improvement in speech recognition threshold and word recognition score was significant in noise and quiet conditions. The all-cause adverse event/complication rate in our series was 10.4%. The most common complications were infections (4.5%) and poorly controlled postoperative pain (3.0%). Hematomas occurred in 1.5% of patients. Reoperation was required in 4 patients; explant in 1. Use of the Osia 2 device in our series has resulted in good hearing outcomes, particularly in terms of high frequency gain. Complication rates were low. To our knowledge, this is the largest study to date reporting on Osia 2 outcomes.

Parent and Child Experiences of Bone-Conduction Hearing Devices for Unilateral Microtia–Atresia: Decisions and Outcomes

Parent and Child Experiences of Bone-Conduction Hearing Devices for Unilateral Microtia–Atresia: Decisions and Outcomes

Outcomes and device use in children with bone-conduction hearing devices in South Africa.

Bone-conduction hearing devices (BCHD) can provide hearing solutions in settings where middle ear pathology is rife. Describe functional hearing outcomes and device use of children fitted with BCHD. Retrospective review of 79 children fitted with BCHD between January 2017 and May 2022. Outcomes included device use and subjective reports measured with the Parents' Evaluation of Aural/Oral Performance of Children (PEACH) and the Teachers' Evaluation of Aural/Oral Performance of Children (TEACH). Analysis of variance established association between mean data logging and type and degree of hearing loss. Thematic analyses were done for qualitative outcomes. Average usage was 7.0 h/day (5.4 SD; range 0.1-24). PEACH ratings indicated 93.3% of children wore their BCHD 'always' or 'often', with 80% displaying Typical auditory performance at 1-month follow-up. TEACH ratings indicated 84.2% of children wore their BCHD 'always' or 'often', with 78.9% showing typical auditory behaviour. Increased usage was noted for conductive, mixed, moderate and severe hearing losses. There was a mean delay of 17.2 months (23.4 SD; range 0-90) between age of diagnosis and fitting. Thematic analyses identified two main themes: advantages and barriers to BCDH use. Average device use fell short of the internationally recommended 10 h/day. Higher BCHD use was associated with higher functional listening performance scores. Long waiting times for medical or surgical intervention for conductive hearing losses can delay BCHD fitting.Contribution:Limited information is available to examine outcomes in children fitted with BCHD.

Surgical repair of congenital aural atresia

Despite the ease, efficacy, predictability, and widespread availability of osseointegrated bone conduction hearing devices, surgical repair of congenital aural atresia (CAA) remains a viable and rewarding operation for patients, parents, and surgeons. Careful selection of patients using appropriate audiometry, detailed radiographic interpretation, and assessment of family understanding and child cooperability are the first steps toward a successful outcome. Intimate knowledge of outer, middle, and inner ear anatomy – both in the normally and abnormally developed ear - coupled with meticulous technique at each stage of the operation can yield outstanding hearing results with a clean, skin-lined, dry, patent ear canal. This chapter reviews the preoperative evaluation and steps of the atresia repair operation, including postoperative management, and provides both predictive and published data on hearing outcomes.

A pilot study on spatial hearing in children with congenital unilateral aural atresia.

Despite normal hearing in one ear, individuals with congenital unilateral aural atresia may perceive difficulties in everyday listening conditions typically containing multiple sound sources. While previous work shows that intervention with bone conduction devices may aid spatial hearing for some children, testing conditions are often arranged to maximize any benefit and are not very similar to daily life. The benefit from amplification on spatial tasks has been found to vary between individuals, for reasons not entirely clear. This study has sought to expand on the limited knowledge on how children with unilateral aural atresia recognize speech masked by competing speech, and how horizontal sound localization accuracy is affected by the degree of unilateral hearing loss and by amplification using unilateral bone conduction devices when fitted before 3 years of age. In a within-subject, repeated measures design, including 11 children (mean age = 7.9 years), bone conduction hearing device (BCD) amplification did not negatively affect horizontal sound localization accuracy. The effect on speech recognition scores showed greater inter-individual variability. No benefit from amplification on a group level was found. There was no association between age at fitting and the benefit of the BCD. For children with poor unaided sound localization accuracy, there was a greater BCD benefit. Unaided localization accuracy increased as a function of decreasing hearing thresholds in the atretic ear. While it is possible that low sound levels in the atretic ear provided access to interaural localization cues for the children with the lowest hearing thresholds, the association has to be further investigated in a larger sample of children.

Influence of Bone Conduction Hearing Device Implantation on Health-Related Quality of Life for Patients with and without Tinnitus.

(1) Background: Tinnitus, often related to hearing loss, is an addressable public health concern affecting health-related quality of life (HRQoL). This study aimed to explore the influence of bone conduction hearing aid (BCHA) implantation on HRQoL and hearing disability in patients with hearing loss suffering from tinnitus. (2) Methods: Data were collected from an international hearing implant registry. Health Utilities Index Mark 3 (HUI-3), Spatial and Qualities of Hearing- 49 Questionnaire (SSQ) and self-reported tinnitus burden data for adult patients implanted with a BCHA (n = 42) who provided baseline as well as follow-up data 1-year post-implantation were extracted from the registry. Wilcoxon signed rank tests and paired samples t-tests were used to analyse outcomes data. (3) Results: Patients, with or without tinnitus, demonstrated clinically important mean improvements in HUI-3 multi-attribute utility scores, HUI-3 hearing attribute and SSQ scores. Hearing loss patients with tinnitus presented with a lower HRQoL than patients without tinnitus. (4) Conclusions: These findings demonstrate the importance of hearing rehabilitation in improving the quality of life and hearing disability of patients with or without tinnitus and in providing tinnitus relief in some patients with hearing loss and tinnitus.

Management of Congenital Aural Atresia and Microtia

Microtia is commonly associated with aural atresia, which will cause cosmetic problems as well as hearing impairment. The management of microtia and aural atresia should improve the aesthetic of the external ear and enhance functional hearing. The reconstruction of the auricle can be performed with autologous rib cartilage or a porous polyethylene framework. Surgeons ideally perform the autologous costal cartilage method at 9 years old or higher considering the development of costal cartilage. For porous polyethylene microtia repair, surgical reconstruction can be performed after 5 years of age. Atresiaplasty can be performed in patients who have normal inner ear function and a well-developed middle ear. The Jahrsdoerfer grading scale is used for assessment of middle ear anatomy and scoring 7 or higher expects good results. The other options for hearing rehabilitation include bone conduction hearing devices or middle ear implants. The surgery for bone conduction devices or middle ear implants can be proposed after 5 years of age. Atresiaplasty is recommended in combination with or after autologous rib graft microtia repair and before porous polyethylene microtia repair. The implantation of the hearing devices should not interfere with auricular reconstruction. It can be performed after autologous rib graft microtia repair or combined with ear elevation.

Estimating vibration artifacts in preclinical experimental assessment of actuator efficiency in bone-conduction hearing devices

ObjectivesTest feasibility of a means to distinguish artifact from relevant signal in an experimental method for pre-clinical assessment of bone conduction (BC) stimulation efficiency based on measurement of intracochlear pressure (ICP). MethodsExperiments were performed on fresh-frozen human temporal bones and cadaver heads. In a first step, fiber optic pressure sensors inserted into the cochlea through cochleostomies were intentionally vibrated to generate relative motion versus the stationary specimen, and the resulting ICP artifact recorded, before and after attaching the sensor fiber to the bone with glue. In a second step, BC stimulation was applied in the conventional location for a commercial bone anchored implant, as well as two alternative locations closer to the otic capsule. Again, ICP was recorded and compared with an estimated artifact, calculated from the previous measurements with intentional vibration of the fiber. ResultsIntentional vibration of the sensor fiber creates relative motion between fiber and bone, as intended, and causes an ICP signal. The stimulus does not create substantial promontory vibration, indicating that the measured ICP is all artifact, i.e. would not occur if the sensor were not in place. Fixating the sensor fiber to the bone with glue reduces the ICP artifact by at least 20 dB. BC stimulation also creates relative motion between sensor fiber and bone, as expected, from which an estimated ICP artifact level can be calculated. The ICP signal measured during BC stimulation is well above the estimated artifact, at least in some specimens and at some frequencies, indicating “real” cochlear stimulation, which would result in an auditory percept in a live subject. Stimulation at the alternative locations closer to the otic capsule appear to result in higher ICP (no statistical analysis performed), indicating a trend towards more efficient stimulation than at the conventional location. ConclusionsIntentional vibration of the fiber optic sensor for measurement of ICP can be used to derive an estimate of the artifact to be expected when measuring ICP during BC stimulation, and to characterize the effectiveness of glues or other means of reducing the artifact caused by relative motion of fiber and bone.

Evaluating the effectiveness of bone conduction hearing implants in rehabilitation of hearing loss.

Implantable hearing devices are indicated for candidates who could not benefit from conventional hearing aids. This study aimed at evaluating their effectiveness in rehabilitation of hearing loss. This study included patients who received bone conduction implants at Tertiary Teaching Hospitals, between December 2018 and November 2020. Data were collected prospectively, and patients were assessed both subjectively using COSI and GHABP questionnaires and objectively using bone conduction and air conduction thresholds, unaided and aided free field speech thresholds. Outcomes of transcutaneous (tBCHD) and percutaneous (pBCHD) bone conduction hearing devices were compared as well as outcomes of unilateral versus bilateral fitting. Postoperative skin complications were recorded and compared. A total of seventy patients were included, thirty-seven of them were implanted with tBCHD and thirty-three with pBCHD. Fifty-five patients were fitted unilaterally compared to 15 bilateral fitting. Preoperative mean of bone conduction (BC) of the overall sample was 23.27 ± 10.91dB, the Air conduction (AC) mean was 69.27 ± 13.75dB. There was significant difference between unaided free field speech score (88.51% ± 7.92) and the aided score (96.79 ± 2.38) with P value = 0.00001. The postoperative assessment using GHABP showed a benefit score mean of 70.95 ± 18.79, patient satisfaction score mean of 78.15 ± 18.39. The disability score improved significantly from a mean of 54.08 ± 15.26 to residual score of only 12.50 ± 10.22 with P < 0.00001 postoperatively. There was significant improvement in all parameters of COSI questionnaire following fitting. Comparison of pBCHDs vs tBCHDs showed a non-significant difference regarding FF speech as well as GHABP parameters. Comparison of the post-operative skin complications was in favor of tBCHDs as (86.5%) of the patients had normal skin postoperatively, compared to 45.5% of patients with pBCHDs devices. Bilateral implantation showed significant improvement of FF speech scores, GHABP satisfaction score, as well as COSI score results. Bone conduction hearing devices are effective solution for rehabilitation of hearing loss. Bilateral fitting yields satisfactory outcomes in suitable candidates. Transcutaneous devices carry significantly lower skin complication rates compared to percutaneous devices.

Improvement in quality of life comparing noninvasive versus invasive hearing rehabilitation in children.

The young population requires early rehabilitation of their hearing loss for normal cognitive, auditive hence social development. All of which, in turn, may have an impact on quality of life (QoL). This study aims to evaluate QoL between two different bone conduction (BC) hearing devices: a noninvasive adhesive hearing aid (Adhear [ADH]) vs. an active transcutaneous implant (Bonebridge [BB]). This study composed of 12 BB and 15 ADH users. Pure tone as well as speech in noise and quiet measurements were evaluated and compared to the Assessment in QoL questionnaire (AQoL-6d). Freefield results showed significant improvements for both devices compared to the unaided condition (p< .0001). Emphasis needs to be drawn on the different unaided level of conductive hearing loss as well as the indication range for both evaluated device groups: the ADH subjects exhibited a mean BC value of 9.50 ± 7.96 dB HL (the indication range up to 25 dB) and the BB subjects a mean of 23.33 ± 25.66 dB HL (the indication range up to 45 dB). Speech perception in quiet and in noise was significantly improved (p< .05; p< .001, respectively). QoL was significantly improved for both treatments (p< .05) but was not different among the devices, and the values were similar to their normal hearing, age, and sex-matched control group. High correlations were found between QoL utility scores and improved PTA4 in the aided condition (r 2 = .8839 and .7810 for BB and ADH, respectively). Our results show that both devices offer significant beneficial audiological rehabilitations with significantly increased QoL. However, the underlying condition and the unaided degree of hearing loss, hence the required higher stimulation must be the deciding factor when opting for a hearing device, and this should be independent of age. 2c.

Ten years' experience with bone conduction hearing aids in the Western Cape, South Africa.

Untreated conductive and mixed hearing losses as a result of middle ear pathology or congenital ear malformations can lead to poor speech, language and academic outcomes in children. Lack of access to centralised hearing healthcare in resource-constrained environments limits opportunities for children with hearing loss. Red Cross War Memorial Children's Hospital (RCWMCH) is one of only two dedicated paediatric hospitals in sub-Saharan Africa. Between 2016 and 2021, 29 children received implanted bone conduction hearing devices, and 104 children were fitted with bone conduction devices on softbands. The authors' experience at RCWMCH suggests that bone-anchored hearing devices, either fitted on softbands or on implanted abutments, can provide solutions in settings where patients have limited access to hearing healthcare and optimal classroom environments. Hearing healthcare should be accessible and delivered at the appropriate level of care to mitigate the adverse effects of hearing loss in children.Contribution:This article describes strategies employed at RCWMCH such as fitting bone conduction hearing devices on a softband immediately after hearing loss diagnosis and conducting follow-up via remote technology to make hearing healthcare more accessible to vulnerable populations.

Modern Advances in Bone Conduction–Hearing Devices

Modern Advances in Bone Conduction–Hearing Devices

Efficient Bone Conduction Hearing Device With a Novel Piezoelectric Transducer Using Skin as an Electrode.

Bone conduction hearing aids are the only non-surgical devices used for conductive hearing loss. However, they are impractical for lifelong use since they require close contact of the transducer with the head skin, causing skin erosion and discomfort. Bone conduction hearing implants and active middle ear implants do not present these issues; however, they require surgery and can sometimes cause issues in the skin surrounding the devices. This study aimed to develop a new bone conduction hearing device that does not exert pressure on the skin or require surgery. Our device modified a piezoelectric element by using the skin of a pinna as one of the two electrodes of a conventional piezoelectric device. We compared the sound transmission of a speaker, a conventional piezoelectric device, or the new device to the Guinea pig cochlea, a physiological sound transducer to the auditory nerve, in normal and air-conductive hearing loss conditions. The novel device transmitted sound to the cochlea even after causing air-conductive hearing loss. Its bone conduction was more efficient than the speaker and the conventional piezoelectric device. We developed a novel type of bone conduction device that efficiently transmits sound to the cochlea by skipping the external auditory canal, tympanic membrane, and middle ear ossicles. This device does not exert pressure on the skin that can result in skin damage, an adverse effect of a conventional bone conduction hearing aid. Our novel hearing device can be used as a substitute for current bone-conduction hearing devices.

Individual computer-assisted 3D planning for placement of auricular prosthesis anchors in combination with an implantable transcutaneous bone conduction hearing device in patients with aural atresia.

The simultaneous implantation of the Bonebridge (MED-EL, Innsbruck, Austria), asemi-implantable active transcutaneous bone conduction hearing device and anchors for auricular prostheses can be challenging as both implants contain magnets and compete for the narrow space in the designated implantation area. Apreoperative planning tool (virtual surgery) was used with individual 3D computer models of the skull and implants for finding optimal implant positions for both the floating mass transducer (FMT) and the anchors for the auricular prosthesis. The interaction between the magnetic prosthesis anchors and the FMT was measured by means of static magnetic forces. A retrospective data analysis was conducted to evaluate the surgical and audiological outcome. Between 2014 and 2021, a3D planning of a simultaneous implantation of the Bonebridge with auricular prosthesis anchors was conducted on 6 ears of 5 patients (3males, 2females; age range 17-56years). The individual preoperative planning was considered very useful for the optimal placement of bone anchors in combination with the Bonebridge. Audiological data showed aclear benefit for hearing 3months and > 11months after implantation. No adverse interactions between the magnetic prosthesis anchors and the FMT were observed. In two patients, revision surgery was carried out due to skin inflammation or wound healing problems. No long-term complications were observed 3-5 years after surgery. Preoperative 3D planning represents a clear benefit for the simultaneous audiological and esthetic rehabilitation using the Bonebridge and anchors for auricular prostheses.

Hearing Outcomes of a New Cartilage Conduction Device vs Bone Conduction Devices.

To compare audiometric outcomes of a new cartilage conduction hearing device (CCD) with traditional bone conduction hearing devices (BCDs). Clinical trial and crossover study design. Tertiary academic center. Sixteen adults (19 ears) with congenital aural atresia or overclosed ear canals who previously underwent BCD implantation were fitted with a CCD. Audiometric data were collected with use of the BCD and the CCD. The mean pretreatment 4-frequency pure tone average was 81 dB. The mean aided pure tone averages with the BCD and CCD were 27 and 32 dB (P = .002), and the mean functional gains were 54 and 49 dB (P = .002), respectively. The mean consonant-nucleus-consonant scores with the BCD were 90% (best aided) and 80% (aided ear isolated), and those with the CCD were 86% and 76%. Mean AzBio scores were 90% (quiet), 77% (+10 dB SNR [signal to noise ratio]), and 52% (+5 dB SNR) when isolating the BCD ear and 90%, 73%, and 41% when isolating the CCD ear. No difference in speech scores achieved statistical significance except the AzBio isolated to the aided ear in the +5-dB SNR condition, which favored the BCD (P = .01). Pure tone audiometric outcomes with the BCD show a small advantage over the CCD, with the difference driven mainly by high-frequency responses. Speech outcomes were equivalent apart from the +5-db SNR condition, which favored the BCD.

Individual computer-assisted 3D planning for placement of auricular prosthesis anchors in combination with an implantable transcutaneous bone conduction hearing device in patients with aural atresia. German version

The simultaneous implantation of the Bonebridge (MED-EL, Innsbruck, Austria), asemi-implantable active transcutaneous bone conduction hearing device and anchors for auricular prostheses can be challenging as both implants contain magnets and compete for the narrow space in the designated implantation area. Apreoperative planning tool (virtual surgery) was used with individual 3D computer models of the skull and implants for finding optimal implant positions for both the floating mass transducer (FMT) and the anchors for the auricular prosthesis. The interaction between the magnetic prosthesis anchors and the FMT was measured by means of static magnetic forces. A retrospective data analysis was conducted to evaluate the surgical and audiological outcome. Between 2014 and 2021 a3D planning of a simultaneous implantation of the Bonebridge with auricular prosthesis anchors was conducted on 6 ears of 5 patients (3males, 2females; age range 17-56years). The individual preoperative planning was considered very useful for the optimal placement of bone anchors in combination with the Bonebridge. Audiological data showed aclear benefit for hearing 3months and > 11months after implantation. No adverse interactions between the magnetic prosthesis anchors and the FMT were observed. In two patients, revision surgery was carried out due to skin inflammation or wound healing problems. No long-term complications were observed 3-5 years after surgery. Preoperative 3D planning represents a clear benefit for the simultaneous audiological and esthetic rehabilitation using the Bonebridge and anchors for auricular prostheses.

Bone Conduction Hearing Aid

Abstract: The GSM based Soundbite hearing system allows people with hearing disability to hear the sounds via bone conduction to wear an intraoral device and a small microphone in the deaf ear to regain lost hearing. This device consists of GSM modem, PIC16F877A controller and audio amplifier unit. GSM modem will receive incoming calls and automatically answer the call via AT Commands. Then incoming voice signal is converted into low frequency vibration signal that fed through the teeth to cochlea. Unlike implantable bone conduction hearing aids, Sound Bite requires no surgery. Rather, it is the world’s first removable and non-surgical hearing solution to use the well-established principle of bone conduction to imperceptibly transmit sound via the teeth. Custom made for each person, Sound Bite is simple, removable, and totally non-invasive. This paper introduces a novel hearing aid named artificial ultrasonic bone conduction hearing device, which is different from the traditional hearing aid in two sides: 1) sound conduction manner, 2) human perceptive principles. We focus on discussing the structure of the hearing aid and the research of frequency transposition algorithm. In addition, we design algorithm experimental platform and some sample electromechanical transducers.

Differing Bilateral Benefits for Spatial Release From Masking and Sound Localization Accuracy Using Bone Conduction Devices.

Objectives:Normal binaural hearing facilitates spatial hearing and therefore many everyday listening tasks, such as understanding speech against a backdrop of competing sounds originating from various locations, and localization of sounds. For stimulation with bone conduction hearing devices (BCD), used to alleviate conductive hearing losses, limited transcranial attenuation results in cross-stimulation so that both cochleae are stimulated from the position of the bone conduction transducer. As such, interaural time and level differences, hallmarks of binaural hearing, are unpredictable at the level of the inner ears. The aim of this study was to compare spatial hearing by unilateral and bilateral BCD stimulation in normal-hearing listeners with simulated bilateral conductive hearing loss.Design:Bilateral conductive hearing loss was reversibly induced in 25 subjects (mean age = 28.5 years) with air conduction and bone conduction (BC) pure-tone averages across 0.5, 1, 2, and 4 kHz (PTA4) <5 dB HL. The mean (SD) PTA4 for the simulated conductive hearing loss was 48.2 dB (3.8 dB). Subjects participated in a speech-in-speech task and a horizontal sound localization task in a within-subject repeated measures design (unilateral and bilateral bone conduction stimulation) using Baha 5 clinical sound processors on a softband. For the speech-in-speech task, the main outcome measure was the threshold for 40% correct speech recognition when masking speech and target speech were both colocated (0°) and spatially and symmetrically separated (target 0°, maskers ±30° and ±150°). Spatial release from masking was quantified as the difference between colocated and separated masking and target speech thresholds. For the localization task, the main outcome measure was the overall variance in localization accuracy quantified as an error index (0.0 = perfect performance; 1.0 = random performance). Four stimuli providing various spatial cues were used in the sound localization task.Results:The bilateral BCD benefit for recognition thresholds of speech in competing speech was statistically significant but small regardless if the masking speech signals were colocated with, or spatially and symmetrically separated from, the target speech. Spatial release from masking was identical for unilateral and bilateral conditions, and significantly different from zero. A distinct bilateral BCD sound localization benefit existed but varied in magnitude across stimuli. The smallest benefit occurred for a low-frequency stimulus (octave-filtered noise, CF = 0.5 kHz), and the largest benefit occurred for unmodulated broadband and narrowband (octave-filtered noise, CF = 4.0 kHz) stimuli. Sound localization by unilateral BCD was poor across stimuli.Conclusions:Results suggest that the well-known transcranial transmission of BC sound affects bilateral BCD benefits for spatial processing of sound in differing ways. Results further suggest that patients with bilateral conductive hearing loss and BC thresholds within the normal range may benefit from a bilateral fitting of BCD, particularly for horizontal localization of sounds.