Robert Cowan

Risks to the hearing health of patrons and staff in the music industry have been well documented and in recent years, regulations have been introduced in a number of European countries as a means of limiting sound exposure for attendees at live music events such as gigs, concerts and festivals. In Australia, sound levels at live music venues are generally stipulated in planning permits and/or liquor licenses but are largely focussed on preventing the emission of sound to neighbouring premises rather than reducing risks to hearing of patrons or staff. In this study, we investigated the use of a sound level management system (10EaZy) as a way of reducing exposure levels for patrons and staff, without interfering with patrons' enjoyment of the musical performances. More than 200 sound level measurements were taken in six inner-city Melbourne venues during live music performances before and after installation of the 10EaZy system at each venue. Measurements from the before-and after...

With the increased recognition of potential damage to listeners when subjected to excessively loud sound, software-based sound level management systems can be viewed as a component of a strategy for reducing sound exposure to patrons and staff in live music venues. However, the use of level management tools in small indoor music venues, which represent a unique environment, has not been systematically explored. In an experimental approach for sound level management, a software system was tried in six indoor live-music venues in Melbourne. Comparing a control (without sound level management software) and the experimental condition (using the software), there was no reduction in mean LAeq,T, although there was a reduction in the number of events with extreme volume levels. Subjective questionnaires indicated that one-fifth of the patrons preferred lower sound levels than they experienced. The findings suggest that modifications to the software system may be necessary if the aim of the system is to reduce patron and staff sound exposure rather than simply to avoid exceeding legislative sound level limits. Recommended alterations could include greater flexibility in choice of target, matching with context of the performance, or changes to the system's visual display so that staying below, not at target, is positively reinforced.

Many reports have established that hearing-impaired children using the Nucleus 22-channel cochlear implant may show both significant benefits to lipreading and significant scores on open-set words and sentences using electrical stimulation only. These findings have raised questions about whether severely or severely-to-profoundly deaf children should be candidates for cochlear implants. To study this question, postoperative results for implanted children with different levels of preoperative residual hearing were evaluated in terms of speech perception benefits. A retrospective study of the first 117 children, sequentially, to undergo implantation in the Melbourne and Sydney Cochlear Implant Clinics was undertaken. All children had been assessed by and received their implants in a tertiary referral centre. To assess aided residual hearing, the children were grouped into four categories of hearing on the basis of their aided residual hearing thresholds measured preoperatively. To ass...

Objectives To evaluate the potential risk of pneumococcal meningitis associated with the use of a dexamethasone-eluting intracochlear electrode array as compared with a control array. Methods In two phases, adult Hooded-Wistar rats were implanted via the middle ear with an intracochlear array and were inoculated with Streptococcus pneumoniae 5 days post-surgery. Phase I created a dosing curve by implanting five groups (n = 6) with a control array, then inoculating 5 days later with different numbers of S. pneumoniae: 0 CFU, 10(3) CFU, 10(4) CFU, 10(4) CFU repeated, or 10(5) CFU (colony forming units). A target infection rate of 20% was aimed for and 10(4) CFU was the closest to this target with 33% infection rate. In phase II, we implanted two groups (n = 10), one with a dexamethasone-eluting array, the other a control array, and both groups were inoculated with 10(4) CFU of S. pneumoniae 5 days post-surgery. Results The dexamethasone-eluting array group had a 40% infection rate; th...

To evaluate the effectiveness and issues associated with a research totally implantable cochlear implant (TIKI). Limited patient trial. Tertiary referral center. Three adult human subjects with severe-to-profound sensorineural hearing loss. Subjects were implanted with a research TIKI developed by Cochlear Limited and the Co-operative Research Centre for Cochlear Implant and Hearing Aid Innovation. The TIKI has a lithium ion rechargeable battery, a package-mounted internal microphone, and sound-processing electronics that enable the use of "invisible hearing" without the use of an external device. The TIKI also functions with an external ESPrit 3G sound processor as a conventional cochlear implant. The standard surgical technique was modified to accommodate the larger device package. Postoperatively, subjects used TIKI in both invisible hearing and the conventional ESPrit 3G modes. Device use was recorded in both invisible hearing and ESPrit 3G listening modes. Performance...

Adult-onset hearing loss is insidious and typically diagnosed and managed several years after onset. Often, this is after the loss having led to multiple negative consequences including effects on employment, depressive symptoms, and increased risk of mortality. In contrast, the use of hearing aids is associated with reduced depression, longer life expectancy, and retention in the workplace. Despite this, several studies indicate high levels of unmet need for hearing health services in older adults and poor use of prescribed hearing aids, often leading to their abandonment. In Australia, the largest component of financial cost of hearing loss (excluding the loss of well-being) is due to lost workplace productivity. Nonetheless, the Australian public health system does not have an effective and sustainable hearing screening strategy to tackle the problem of poor detection of adult-onset hearing loss. Given the increasing prevalence and disease burden of hearing impairment in adults, ...

and social impact, as well as carrying a broad fi nancial cost to the individual and the State. The HEARing Cooperative Research Centre, fi rst established in 1992, is a collaboration of some twenty-fi ve member organizations, including universities, hearing healthcare industry, government services and research, clinical agencies and hospitals, early intervention centres, and professional audiologists, focused on the twin challenges of more effective prevention and improved remediation of hearing loss. Some eight years ago, we realized that although newborn hearing screening was progressively being introduced around the world, and seemed likely in principle to benefi t hearing-impaired children, the evidence base to support its indefi nite retention was scant. We also realized that a window of opportunity existed to conduct a controlled study of its effi cacy that was unlikely to ever be repeated. Across Australia, different states were at various stages of implementing or preparing for newborn screening programs. However, regardless of the age at which hearing loss was detected, children in Australia nationally received uniform, high quality, free audiological rehabilitation services. This meant that children could be enrolled prospectively in a long-term study at a time when some had access to newborn screening while others didn ’ t. We also recognized that through the HEARing CRC and its members, in particular Australian Hearing, we had in place a collaboration that could not only enrol children immediately after their hearing loss was detected, but could systematically follow up these children over a longterm study period and coordinate a large scale investigation protocol across multiple sites. From its outset the study was big in ambition. The study needed to include participants who would be representative of the general population of hearing-impaired children in Australia, and so had to include children with other disabilities and from different language backgrounds. The number of children involved had to be large enough to facilitate statistical examination of the many factors that could affect outcomes. Each of these factors had to be documented for each child at the time they were occurring, so the data would be as accurate and complete as possible. Outcomes measured had to include anything that hearing loss could be expected to affect. The study had to be a randomized, controlled, double-blinded design wherever possible. Examination of the impact of newborn screening almost met this goal, as access to it depended only on when and where each child was born. The type of hearing-aid prescription — National Acoustic Laboratories (NAL) versus Desired sensation level (DSL) — was able to be completely randomized and double blinded. Given that the originators of both prescriptions had similar aims for their respective procedures, we should perhaps not be surprised at the fi nding reported in this supplement that the two prescriptions did not lead to different language outcomes, despite their differences in the gain prescribed. Theoretical examinations of this fi nding, and implications of the prescriptions for loudness and their potential to create noise-induced hearing loss, are also examined in papers in this supplement. As the study progressed, the existence of a large, representative cohort of children and their families about whom much was known, and who were willing to have their data used to advance knowledge, made it possible to answer further questions. Blood samples obtained at birth were used to determine the aetiology of the hearing loss for many of the children and to examine its potential relationship to outcomes. The impact of using frequency compression could be assessed in a completely randomized, controlled study by changing over randomly selected children to this type of amplifi cation. As reported in this supplement, the use of frequency compression was not associated with signifi cant difference in language outcomes at age three years. (This question, and others, will be re-examined at age fi ve years.) Surprisingly, the children with auditory neuropathy spectrum disorder did not have outcomes different from those with sensorineural hearing loss once all other known factors (including hearing threshold elevation) were controlled for, as described in detail in this supplement. On a more qualitative level, the impact on parents of having a hearing-impaired child and their reactions to the services given to their children could be studied, as reported in the fi rst paper in the supplement. We hope that the account in this supplement, based on some of the outcomes measured at age three years, is of value to all who provide services to hearing-impaired children. A critical fi nding of the LOCHI study to date is that implantation prior to 12 months of age is critical to maximizing outcomes at age three years. This would be impossible to ensure without access to newborn screening of…

The aim of this study was to utilise micro-focus X-ray fluoroscopy for viewing electrode movement in the cochlea. Various prototypes of newly designed cochlear implant electrodes were evaluated during insertion studies on human cadaver temporal bones. The magnified fluoroscopic images were observed in real-time and recorded for retrospective studies. In 30 insertions of hearing preservation (Hybrid-L) arrays, fluoroscopy provided crucial information on the tip design, length of array and stiffening stylet. In 44 insertions of Contour Advance enhanced (CAe) arrays, the length, curvature, depth of insertion and degree of stiffness were assessed. CAe arrays were successfully inserted to the designated depth and positioned close to the modiolus. High quality micro-focus fluoroscopic images of electrode movement in the cochlea greatly assisted in the validation of newly designed intra-cochlear electrode arrays.

Electrode impedance increases following implantation and undergoes transitory reduction with onset of electrical stimulation. The studies in this paper measured the changes in access resistance and polarization impedance in vivo before and following electrical stimulation, and recorded the time course of these changes. Impedance measures recorded in (a) four cats following 6 months of cochlear implant use, and (b) three cochlear implant recipients with 1.5-5 years cochlear implant experience. Both the experimental and clinical data exhibited a reduction in electrode impedance, 20 and 5% respectively, within 15-30 minutes of stimulation onset. The majority of these changes occurred through reduction in polarization impedance. Cessation of stimulation was followed by an equivalent rise in impedance measures within 6-12 hours. Stimulus-induced reductions in impedance exhibit a rapid onset and are evident in both chronic in vivo models tested, even several years after implantation. Given the impedance changes were dominated by the polarization component, these findings suggest that the electrical stimulation altered the electrode surface rather than the bulk tissue and fluid in the cochlea.

The Optimized Pitch and Language (OPAL) strategy enhances pitch perception through coding of fundamental frequency (F0) amplitude modulation information in the stimulus envelope delivered to a cochlear implant. Previous research using a prototype of the strategy demonstrated significant benefits in musical pitch and lexical tone discrimination tasks with no degradation in speech recognition when compared with the clinical Advanced Combination Encoder (ACE) strategy in a small group of subjects. Based on those studies, a modified version of the strategy was implemented in the commercial Nucleus CP900 series processor. The aims of the present study were to establish whether the CP900 OPAL implementation continued to provide improved F0 pitch perception in a speech intonation task with no degradation to speech perception in quiet and noise, when compared with the clinical ACE strategy in a larger cohort of subjects. Further aims were to evaluate fitting procedures and subject acclimatization to the strategy after take-home experience. Twenty experienced adult cochlear implant recipients were enrolled in the study. Two subjects withdrew during the study leaving 18 sets of data for analysis. A repeated-measures single-subject design with take-home experience was used to test for improved speech intonation perception using OPAL compared with ACE and for comparable performance between strategies for open-set word recognition in quiet at two presentation levels, sentence recognition in adaptive 4-talker babble noise, and speech intelligibility ratings. The stimulation rate employed for OPAL was 1200 pulses per second/channel which was higher than the default clinical rate of 900 pulses per second/channel used for ACE by all subjects in the present study. Two variations of the OPAL "F0 restore gain" (the gain applied to restore the loudness of modulated channels) were investigated: "custom" measured per subject and "default" which was the average of all subject custom gains. A significant group mean benefit on the intonation test of 8.5% points was shown for OPAL compared with ACE. There was a significant period of adaptation to OPAL with significantly poorer sentence in noise scores acutely and after only 2 weeks of take-home experience. After 4 weeks of take-home experience, comparable word perception in quiet and sentence perception in noise for OPAL were obtained. Furthermore, there was good subject acceptability in the field with comparable speech intelligibility ratings between strategies. Results of the fitting procedure showed that OPAL did not require any additional steps compared with fitting of ACE. A default F0 restore gain provided comparable outcomes to a custom gain setting. The CP900 OPAL implementation provided a significant benefit to perception of speech intonation when compared with ACE. Comparable speech perception (in quiet and noise) and subjective ratings of speech intelligibility between strategies were also achieved after a period of acclimatization. These outcomes are consistent with results of earlier studies using prototype versions of the strategy and reaffirm its potential for improvement of F0 pitch perception in speech while preserving coding of segmental speech information. Furthermore, the OPAL strategy can be programmed into subject's processors using the same fitting procedures used for ACE thereby simplifying its adoption in clinical settings.

ABSTRACT A small Platinum (Pt) electrode (geometric area: ~0.43 mm2) was treated in an electrochemical etching process, to produce a highly porous columnar thin layer (~600 nm) on the surface of the electrode. The modified Pt electrode (Pt-p) showed similar electrical properties to a platinum-black electrode but with high mechanical integrity. Previous studies of chronic stimulation had also shown good biocompatibility and surface stability over several months implantation. This paper discusses the potential applications of the modified electrode as an implanted bio-sensor: (1) as a recording electrode compared to an untreated Pt electrode. (2) as a probe in detecting electrical characteristics of living biological material adjacent to the electrode in vivo, which may correlate to inflammation or trauma repair. Results of electrochemical impedance spectroscopy (EIS) revealed much lower electrode interface polarisation impedance, reduced overall electrode impedance, and a largely constant impedance above 100 Hz for the Pt-p electrode compared with untreated Pt electrodes. This provides a platform for recording biological events with low noise interference. Results of A.C. impedance spectroscopy of the high surface area electrode only reflect changes in the surrounding biological environment in the frequency range (1 k Hz to 100 k Hz), interference from electrode polarisation impedance can be neglected. The results imply that the surface-modified electrode is a good candidate for application to implantable biosensors for detecting bio-electric events. The modification procedure and its high surface area concept could have application to a smart MEMS device or microelectrode.

To compare the benefits of a dexamethasone-eluting array for hearing preservation and cochlear histopathology in low trauma (soft-surgery) and high trauma models of cochlear implant surgery. Adult guinea pigs were implanted with an intra-cochlear array using two different surgical procedures: either a soft-surgery approach or following generation of electrode insertion trauma (high trauma). Two methods of dexamethasone delivery were evaluated: elution from an electrode array alone, and elution from a cochlear implant electrode array in combination with a pre-operative systemic injection. All electrode arrays were implanted for a period of 4 weeks. Outcome measures at 4 weeks post-implantation included auditory brainstem response (ABR) thresholds, histological analysis of spiral ganglion neuron density, fibrotic tissue, new bone growth, and cochlear damage. Animals exposed to high surgical trauma showed greater hearing loss than those in the low trauma model, irrespective of the pres...

To examine post-implantation benefit and time taken to acclimate to the cochlear implant for adult candidates with more hearing in the contralateral non-implanted ear than has been previously considered within local candidacy guidelines. Prospective, within-subject experimental design. Forty postlingual hearing-impaired adult subjects with a contralateral ear word score in quiet ranging from 27% to 100% (median 67%). Post-implantation improvement of 2.4 dB and 4.0 dB was observed on a sentence in coincident babble test at presentation levels of 65 and 55 dB SPL respectively, and a 2.1 dB benefit in spatial release from masking (SRM) advantage observed when the noise location favoured the implanted side. Significant post-operative group mean change of between 2.1 and 3.0 was observed on the sub-scales of the speech, spatial, and qualities (SSQ) questionnaire. Degree of post-implantation speech reception threshold (SRT) benefit on the coincident babble test and on perception of soft s...

This study assessed speech perception benefits for three congenitally deaf adolescents who used an electrotactile speech processor (Tickle Talker(TM)) and subsequently went on to use a Nucleus Minisystem 22 cochlear implant. Both devices provided significant and comparable benefits for all children in the device plus lipreading condition. All children benefited from the additional information provided by either the Tickle Talker(TM) or the cochlear implant, and were able to perceive speech information with these devices that was not available through either aided residual hearing or lipreading. None of the three children were able to understand open-set words or sentences using either hearing aids alone or Tickle Talker(TM) alone, without the aid of lipreading. Two of the children showed significant open-set speech perception benefits while using their cochlear implant alone.

The aim of this study was to investigate whether experienced paediatric cochlear implant users could show benefits to speech perception outcomes from the introduction of noise reduction and automated scene classification technologies as implemented in the Nucleus(®) 6 sound processor. Previous research with adult cochlear implant users had shown significant improvements in speech intelligibility for listening in noisy conditions and good user acceptance for upgrading to the Nucleus 6 processor. In adults, these improvements for listening in noise were primarily attributed to the use of a range of new input processing technologies including noise reduction, as well as introduction of automatic scene classification technology. Experienced paediatric cochlear implant users (n=25) were recruited from four clinics located in three countries. Research participants were evaluated on three occasions, an initial session using their Nucleus 5 sound processor; a second session in which participants used the Nucleus 6 processor programmed with the same technologies as were used in their Nucleus 5 sound processor; and a final session in which participants used the Nucleus 6 processor programmed with the default technologies including automatic scene classification (SCAN) which automatically selects the microphone directionality, noise reduction (SNR-NR), and wind noise reduction (WNR) technologies. Prior to both the second and third evaluations, research participants had approximately two weeks take-home experience with the new system. Speech perception performances on monosyllabic word tests presented in quiet and in noise, and a sentence test presented in noise, were compared across the three processor conditions. Acceptance of the Nucleus 6 default settings was assessed in a final session. No group mean difference in performance was found for monosyllabic words in quiet. A significant improvement in speech perception was found for both monosyllabic words and sentences in noise with the default Nucleus 6 program condition as compared with the Nucleus 5 condition. No acceptance issues were noted for any of the children. Experienced paediatric cochlear implant users showed a significant improvement in speech perception in listening in noise when upgraded to the Nucleus 6 sound processor primarily due to the introduction of a noise reduction technology, and all children accepted the default program. These findings suggest that school-aged children may benefit from upgrading to the Nucleus 6 sound processor using the default program.

For a group of cochlear implant recipients, who use hearing aids in the contralateral ear, the benefit of NAL-NL2 relative to a recipients' own prescription was assessed. Whether there was a preferred frequency response and/or gain deviation from NAL-NL2 was then investigated. Speech recognition and self-reported ratings of benefit were examined for the recipients' own prescription compared to the NAL-NL2 prescription, in the bimodal and hearing-aid alone conditions. Paired-comparison of hearing-aid frequency response was conducted with default NAL-NL2 and two variants, a low frequency boost or cut. Using a loudness balancing procedure, the hearing-aid gain required to achieve equal loudness between the devices was measured. Sixteen adults with post-lingual hearing loss. A 22% increase in group median word score in quiet with use of NAL-NL2 in the hearing-aid alone condition. In the bimodal condition there was no improvement with NAL-NL2. Default NAL-NL2 frequency response w...

The aim of the investigation was to prospectively evaluate, in a multicenter setting, the clinical performance of a new magnetic bone conduction hearing implant system. The test device was the Cochlear Baha Attract System (Cochlear Bone Anchored Solutions AB, Mölnlycke, Sweden). Instead of the skin-penetrating abutment of traditional bone conduction hearing implants, the test device uses an implantable and an external magnet to transmit sound from the sound processor (SP) through intact skin to the skull bone. Twenty-seven adult patients with a conductive or mild mixed hearing loss or single-sided sensorineural deafness were included in the clinical investigation across four investigational sites. The patients were followed for 9 months after implantation. The study evaluated efficacy in terms of hearing performance compared with unaided hearing and with hearing with the SP on a softband. Patient benefit, soft tissue status, device retention, and safety parameters were monitored con...

Perception of musical pitch in cochlear implant (CI) systems is relatively poor compared with normal hearing and can be adversely affected by changes in spectral timbre coded by stimulation place. In this study, we evaluated whether the perception of musical pitch could be improved through specific training designed to teach listeners to attend to fundamental frequency (F0) exclusively for judgment of pitch and to spectral envelope exclusively for discrimination of spectral timbre. A computer-based training program to improve musical pitch perception was developed that required listeners to match acoustic patterns of pitch and spectral timbre to visual patterns. Ten adult CI recipients participated: five used the training program and five acted as controls. Before training, F0 and center frequency discrimination for band-limited complex harmonic stimuli presented in the sound field were measured in all subjects using their standard clinical device(s). The F0 tests were conducted wit...

Impedance measurements are commonly performed at the end of cochlear implant surgery, not only to confirm that all electrodes are working but also to monitor the impedances of the newly implanted electrodes. The current method of testing allows the determination of only the overall electrode impedance but not its components, access resistance and polarization impedance. To determine whether any longitudinal change in the electrode impedance is caused by a change in the endocochlear environment or rather caused by a change in the surface quality of the electrode, it is necessary to extract access resistance and polarization impedance. We applied an impedance model that enabled us to calculate access resistance and polarization impedance after measurement of electrode impedance at three points along the voltage waveform. The results show that the value of the components of electrode impedance varied with time after surgery: access resistance increased slowly over time, whereas polarization impedance increased up to Week 2 but decreased after commencement of electrical stimulation at that stage. These results are consistent with the hypothesis that a layer of fibrous tissue forms around the electrode within the cochlear canal, resulting in a slow increase of access resistance, whereas a layer of proteins forms on the surface of the electrode in the early phase after implantation. Electrical stimulation appears to disperse this surface layer, thereby reducing both the polarization impedance and electrode impedance. The method presented enables the extraction of more detailed information about the longitudinal changes in the intracochlear environment after cochlear implantation.

This study introduces and evaluates a method for measurement of the longitudinal spread of electrically evoked neural excitation in the cochlea, using the Neural Response Telemetry system (NRT) available with the Nucleus((R)) 24 cochlear implant system. The recently released version of the NRT software (version 3.0) enables presentation of the 'masker' and 'probe' on different electrodes. In the present method the probe position was fixed, while the masker position was varied across the electrode array. The amplitude of the response to the partially masked probe provides a measure of the amount of masking, which is dependent on the extent of overlap of the excitation regions of the masker and probe. These measurements were performed in seven subjects implanted with the Nucleus 24 cochlear implant system (four with straight and three with Contour electrode arrays), for basal, middle and apical probe electrodes. Similar excitation profiles were obtained using either the standard NRT subtraction paradigm or an alternative 'Miller' method. The excitation profiles were compared with those obtained from psychophysical forward masking and good agreement was found. The widths of electrically evoked compound action potential (ECAP) and forward masking profiles did not differ significantly. Whereas the width of the ECAP measure was significantly correlated with both the maximum comfortable level and the distance of the electrode band from the modiolus, the width of the forward masking profile was not.