Directional Microphone Research Articles

Potential Use of Non-invasive Remote Monitoring of Electronically-measured S3 Heart Sounds for Heart Failure Management

Background The third heart sound (S3) is known as a very specific clinical sign for heart failure and is associated with worse clinical outcomes. In the context of heart failure (HF) the presence of a pronounced or audible S3 is a specific sign of elevated filling pressures and is suggestive of a restrictive filling pattern with a steep transmitral E‐wave. Recent work has demonstrated that implantable device-based S3 measurements in the inaudible range, in implantable devices, may be even more predictive of clinical outcomes. Methods Using the Nanowear wearable diagnostic device containing a directional microelectronic machine microphone and electrocardiogram (ECG) capability, we report a system that can effectively detect heart sounds. Results Heart sounds and ECG were measured in a 74-year-old female with Heart Failure with Preserved Ejection Fraction admitted for acute on chronic heart failure exacerbation. S3 was isolated using a search window using ECG tracing for identification of S1 and S2 (Figure 1A). Ensemble heart sounds were plotted and root mean square (RMS) mean, in mVolts (mV), were calculated for S3 in sitting (63 mV), supine (250.5 mV) and right lateral decubitus (135.2 mV) positions (Figure 1B, C). Conclusion We report an accurate method, using the Nanowear device, to electronically measure heart sounds that is positionally sensitive. Invasively-measured S3 heart sounds correlate with clinical outcomes, however their utility is limited to patients with implantable cardioverter defibrillator or cardiac resynchronization therapy devices. Future studies may validate non-invasive remote monitoring of S3 heart sounds as a management tool for heart failure patients.

Contribution of noise reduction pre-processing and microphone directionality strategies in the speech recognition in noise in adult cochlear implant users.

Refinement currently offered in new sound processors may improve noise listening capability reducing constant background noise and enhancing listening in challenging signal-to-noise conditions. This study aimed to identify whether the new version of speech processor preprocessing strategy contributes to speech recognition in background noise compared to the previous generation processor. This was a multicentric prospective cross-sectional study. Post-lingually deaf adult patients, with at least 1year of device use and speech recognition scores above 60% on HINT sentences in quiet were invited. Speech recognition performance in quiet and in noise with sound processors with previous and recent technologies was assessed under four conditions with speech coming from the front: (a) quiet (b) fixed noise coming from the front, (c) fixed noise coming from the back, and (d) adaptive noise ratios with noise coming from the front. Forty-seven cochlear implant users were included. No significant difference was found in quiet condition. Performance with the new processor was statistically better than the previous sound processor in all three noisy conditions (p < 0.05). With fixed noise coming from the back condition, speech recognition was 62.9% with the previous technology and 73.5% on the new one (p < 0.05). The mean speech recognition in noise was also statistically higher, with 5.8dB and 7.1dB for the newer and older technologies (p < 0.05), respectively. New technology has shown to provide benefits regarding speech recognition in noise. In addition, the new background noise reduction technology, has shown to be effective and improves speech recognition in situations of more intense noise coming from behind.

Effect of Microphone Location and Beamforming Technology on Speech Recognition in Pediatric Cochlear Implant Recipients.

Despite improvements in cochlear implant (CI) technology, pediatric CI recipients continue to have more difficulty understanding speech than their typically hearing peers in background noise. A variety of strategies have been evaluated to help mitigate this disparity, such as signal processing, remote microphone technology, and microphone placement. Previous studies regarding microphone placement used speech processors that are now dated, and most studies investigating the improvement of speech recognition in background noise included adult listeners only. The purpose of the present study was to investigate the effects of microphone location and beamforming technology on speech understanding for pediatric CI recipients in noise. A prospective, repeated-measures, within-participant design was used to compare performance across listening conditions. A total of nine children (aged 6.6 to 15.3 years) with at least one Advanced Bionics CI were recruited for this study. The Basic English Lexicon Sentences and AzBio Sentences were presented at 0o azimuth at 65-dB SPL in +5 signal-to-noise ratio noise presented from seven speakers using the R-SPACE system (Advanced Bionics, Valencia, CA). Performance was compared across three omnidirectional microphone configurations (processor microphone, T-Mic 2, and processor + T-Mic 2) and two directional microphone configurations (UltraZoom and auto UltraZoom). The two youngest participants were not tested in the directional microphone configurations. No significant differences were found between the various omnidirectional microphone configurations. UltraZoom provided significant benefit over all omnidirectional microphone configurations (T-Mic 2, p = 0.004, processor microphone, p < 0.001, and processor microphone + T-Mic 2, p = 0.018) but was not significantly different from auto UltraZoom (p = 0.176). All omnidirectional microphone configurations yielded similar performance, suggesting that a child's listening performance in noise will not be compromised by choosing the microphone configuration best suited for the child. UltraZoom (adaptive beamformer) yielded higher performance than all omnidirectional microphones in moderate background noise for adolescents aged 9 to 15 years. The implications of these data suggest that for older children who are able to reliably use manual controls, UltraZoom will yield significantly higher performance in background noise when the target is in front of the listener.

Effects of Directional Microphone and Noise Reduction on Subcortical and Cortical Auditory-Evoked Potentials in Older Listeners With Hearing Loss.

Understanding how signal processing influences neural activity in the brain with hearing loss is relevant to the design and evaluation of features intended to alleviate speech-in-noise deficits faced by many hearing aid wearers. Here, we examine whether hearing aid processing schemes that are designed to improve speech-in-noise intelligibility (i.e., directional microphone and noise reduction) also improve electrophysiological indices of speech processing in older listeners with hearing loss. The study followed a double-blind within-subjects design. A sample of 19 older adults (8 females; mean age = 73.6 years, range = 56-86 years; 17 experienced hearing aid users) with a moderate to severe sensorineural hearing impairment participated in the experiment. Auditory-evoked potentials associated with processing in cortex (P1-N1-P2) and subcortex (frequency-following response) were measured over the course of two 2-hour visits. Listeners were presented with sequences of the consonant-vowel syllable /da/ in continuous speech-shaped noise at signal to noise ratios (SNRs) of 0, +5, and +10 dB. Speech and noise stimuli were pre-recorded using a Knowles Electronics Manikin for Acoustic Research (KEMAR) head and torso simulator outfitted with hearing aids programmed for each listener's loss. The study aid programs were set according to 4 conditions: (1) omnidirectional microphone, (2) omnidirectional microphone with noise reduction, (3) directional microphone, and (4) directional microphone with noise reduction. For each hearing aid condition, speech was presented from a loudspeaker located at 1 m directly in front of KEMAR (i.e., 0° in the azimuth) at 75 dB SPL and noise was presented from a matching loudspeaker located at 1 m directly behind KEMAR (i.e., 180° in the azimuth). Recorded stimulus sequences were normalized for speech level across conditions and presented to listeners over electromagnetically shielded ER-2 ear-insert transducers. Presentation levels were calibrated to match the output of listeners' study aids. Cortical components from listeners with hearing loss were enhanced with improving SNR and with use of a directional microphone and noise reduction. On the other hand, subcortical components did not show sensitivity to SNR or microphone mode but did show enhanced encoding of temporal fine structure of speech for conditions where noise reduction was enabled. These results suggest that auditory-evoked potentials may be useful in evaluating the benefit of different noise-mitigating hearing aid features.

Sound Source Localization in 2D Using a Pair of Bio–Inspired MEMS Directional Microphones

The majority of fly Ormia ochracea inspired sound source localization (SSL) works are limited to 1D, and therefore SSL in 2D can include a new vision for ambiguous acoustic applications. This article reports on an analytical and experimental work on SSL in 2D using a pair of fly O. ochracea inspired MEMS directional microphones. The reported directional microphones were designed identically in circular shape and operated using piezoelectric sensing in 3-3 transducer mode. In X-Y plane, they were canted in a 90° phase difference, i.e., one microphone was in X-axis and another one was in Y-axis. As a result, their directionality results from the X-axis (cosine) and Y-axis (sine) formulated the tangent dependent 2D SSL in the X-Y plane. The highest accuracy of the SSL in 2D was found to be ±2.92° at bending frequency (11.9 kHz) followed by a ±3.25° accuracy at rocking frequency (6.4 kHz), a ±4.68° accuracy at 1 kHz frequency, and a ±6.91° accuracy at 18 kHz frequency. The subjected frequencies were selected based on the measured inter-aural sensitivity difference (mISD) which showed a proportional impact on the cue of 2D SSL, i.e., the directionality. Besides, the basic acoustic functionalities, such as sensitivity, SNR, and self-noise were found to be 20.86 mV/Pa, 66.4 dB, and 27.6 dB SPL, respectively at 1 kHz frequency and 1 Pa sound pressure. Considering this trend of microphones, the outstanding contribution of this work is the SSL in 2D with higher accuracy using a pair of high performing bio-inspired directional microphones.

Acclimatization to Hearing Aids by Older Adults.

Audiologists and hearing aid users (HAUs) generally agree that an adaptation period is needed following the first hearing aid (HA) experience. The main purpose of this study is to investigate the acclimatization of older adult listeners with hearing loss to HAs using listening effort and behavioral measures. Participants (N=47) were older adults with mild to moderately severe sensorineural hearing loss. Thirty-two participants were new HAUs and 15 participants were experienced HAUs. New HAUs were randomly assigned to one of two groups: noise reduction algorithms and directional microphones activated or noise reduction algorithms and directional microphones deactivated. Speech recognition in noise and listening effort were assessed on 8 different occasions during a 10-month period. A dual-task paradigm was used to measure the listening effort deployed to recognize speech in noise. The primary task consisted of the Hearing in Noise Test which also served as the behavioral speech in noise measure. The secondary task was a tactile pattern-recognition task in which participants had to identify a sequence of three tactile stimuli that varied in duration. The two listening effort outcomes were the proportional dual-task cost and the response time on the secondary task. Cognitive abilities, including working memory and speed of processing, were evaluated using the Reading Span Test and the Digit Symbol Substitution Test, respectively. Results show a significant time*group interaction. Both groups of new HAUs showed improvement over time in speech in noise performances (change of ~2 dB signal to noise ratio) and the experienced HAUs did not improve over time. The acclimatization effect was observed over a period of 4 weeks. There was no significant change over time on both measures of listening effort. There was no association between amplitude of acclimatization and the cognitive abilities measured. An acclimatization effect following HA experience was observed. Specifically, the new HAUs displayed a clinically significant change of 2 dB in signal to noise ratio on the Hearing in Noise Test 4 weeks following their initial fitting. The acclimatization effect is not correlated to cognitive abilities.

Pinna-Imitating Microphone Directionality Improves Sound Localization and Discrimination in Bilateral Cochlear Implant Users

To compare the sound-source localization, discrimination, and tracking performance of bilateral cochlear implant users with omnidirectional (OMNI) and pinna-imitating (PI) microphone directionality modes. Twelve experienced bilateral cochlear implant users participated in the study. Their audio processors were fitted with two different programs featuring either the OMNI or PI mode. Each subject performed static and dynamic sound field spatial hearing tests in the horizontal plane. The static tests consisted of an absolute sound localization test and a minimum audible angle test, which was measured at eight azimuth directions. Dynamic sound tracking ability was evaluated by the subject correctly indicating the direction of a moving stimulus along two circular paths around the subject. PI mode led to statistically significant sound localization and discrimination improvements. For static sound localization, the greatest benefit was a reduction in the number of front-back confusions. The front-back confusion rate was reduced from 47% with OMNI mode to 35% with PI mode (p = 0.03). The ability to discriminate sound sources straight to the sides (90° and 270° angle) was only possible with PI mode. The averaged minimum audible angle value for the 90° and 270° angle positions decreased from a 75.5° to a 37.7° angle when PI mode was used (p < 0.001). Furthermore, a non-significant trend towards an improvement in the ability to track moving sound sources was observed for both trajectories tested (p = 0.34 and p = 0.27). Our results demonstrate that PI mode can lead to improved spatial hearing performance in bilateral cochlear implant users, mainly as a consequence of improved front-back discrimination with PI mode.

Sound source localization by Ormia ochracea inspired low\u2013noise piezoelectric MEMS directional microphone

The single-tone sound source localization (SSL) by majority of fly Ormia ochracea’s ears–inspired directional microphones leaves a limited choice when an application like hearing aid (HA) demands broadband SSL. Here, a piezoelectric MEMS directional microphone using a modified mechanical model of fly’s ear has been presented with primary focus to achieve SSL in most sensitive audio bands to mitigate the constraints of traditional SSL works. In the modified model, two optimized rectangular diaphragms have been pivoted by four optimized torsional beams; while the backside of the whole structure has been etched. As a result, the SSL relative to angular rotation of the incoming sound depicts the cosine dependency as an ideal pressure–gradient sensor. At the same time, the mechanical coupling leads the magnitude difference between two diaphragms which has been accounted as SSL in frequency domain. The idea behind this work has been analytical simulated first, and with the convincing mechanical results, the designed bio–inspired directional microphone (BDM) has been fabricated using commercially available MEMSCAP based on PiezoMUMPS processes. In an anechoic chamber, the fabricated device has been excited in free-field sound, and the SSL at 1 kHz frequency, rocking frequency, bending frequency, and in-between rocking and bending frequencies has been found in full compliance with the given angle of incidence of sound. With the measured inter-aural sensitivity difference (mISD) and directionality, the developed BDM has been demonstrated as a practical SSL device, and the results have been found in a perfect match with the given angle of incidence of sound. Furthermore, to facilitate the SSL in noisy environment, the noise has been optimized in all scopes, like the geometry of the diaphragm, supportive torsional beam, and sensing. As a result, the A-weighted noise of this work has been found less than 23 dBA across the audio bands, and the equivalent-input noise (EIN) has been found to be 25.52 dB SPL at 1 kHz frequency which are the lowest ever reported by a similar device. With the developed SSL in broadband–in addition to the lowest noise–the developed device can be extended in some audio applications like an HA device.

Effect of Microphone Configuration and Sound Source Location on Speech Recognition for Adult Cochlear Implant Users with Current-Generation Sound Processors.

Microphone location has been shown to influence speech recognition with a microphone placed at the entrance to the ear canal yielding higher levels of speech recognition than top-of-the-pinna placement. Although this work is currently influencing cochlear implant programming practices, prior studies were completed with previous-generation microphone and sound processor technology. Consequently, the applicability of prior studies to current clinical practice is unclear. To investigate how microphone location (e.g., at the entrance to the ear canal, at the top of the pinna), speech-source location, and configuration (e.g., omnidirectional, directional) influence speech recognition for adult CI recipients with the latest in sound processor technology. Single-center prospective study using a within-subjects, repeated-measures design. Eleven experienced adult Advanced Bionics cochlear implant recipients (five bilateral, six bimodal) using a Naída CI Q90 sound processor were recruited for this study. Sentences were presented from a single loudspeaker at 65 dBA for source azimuths of 0°, 90°, or 270° with semidiffuse noise originating from the remaining loudspeakers in the R-SPACE array. Individualized signal-to-noise ratios were determined to obtain 50% correct in the unilateral cochlear implant condition with the signal at 0°. Performance was compared across the following microphone sources: T-Mic 2, integrated processor microphone (formerly behind-the-ear mic), processor microphone + T-Mic 2, and two types of beamforming: monaural, adaptive beamforming (UltraZoom) and binaural beamforming (StereoZoom). Repeated-measures analyses were completed for both speech recognition and microphone output for each microphone location and configuration as well as sound source location. A two-way analysis of variance using mic and azimuth as the independent variables and output for pink noise as the dependent variable was used to characterize the acoustic output characteristics of each microphone source. No significant differences in speech recognition across omnidirectional mic location at any source azimuth or listening condition were observed. Secondary findings were (1) omnidirectional microphone configurations afforded significantly higher speech recognition for conditions in which speech was directed to ± 90° (when compared with directional microphone configurations), (2) omnidirectional microphone output was significantly greater when the signal was presented off-axis, and (3) processor microphone output was significantly greater than T-Mic 2 when the sound originated from 0°, which contributed to better aided detection at 2 and 6 kHz with the processor microphone in this group. Unlike previous-generation microphones, we found no statistically significant effect of microphone location on speech recognition in noise from any source azimuth. Directional microphones significantly improved speech recognition in the most difficult listening environments.

Estimating Real-World Performance of Percutaneously Coupled Bone-Conduction Device Users With Severe-to-Profound Unilateral Hearing Loss.

Purpose The bone-conduction device attached to a percutaneous screw (BCD) is an important treatment option for individuals with severe-to-profound unilateral hearing loss (UHL). Clinicians may use subjective questionnaires and speech-in-noise measures to evaluate BCD use in this patient population; however, the translation of these metrics to real-world aided performance is unclear. The purpose of this study was twofold: first, to measure speech-in-noise performance in BCD users with severe-to-profound UHL in a simulated real-world environment, relative to individuals with normal hearing bilaterally; second, to determine if BCD users' subjective reports of aided performance relate to simulated real-world performance. Method A between-subjects design with two groups was conducted with 14 adults with severe-to-profound UHL (BCD group) and 10 age-matched participants with normal hearing bilaterally (control group). Speech-in-noise tests were administered in an eight-speaker R-Space simulating a real-world environment. To further explore speech-in-noise evaluation methods for this population, testing was also completed in a clinically common two-speaker array. The effects of various microphone settings on performance were explored for BCD users. Subjective performance was measured with the Abbreviated Profile of Hearing Aid Benefit (APHAB; Cox & Alexander, 1995) and the Speech, Spatial and Qualities of Hearing Scale (Gatehouse & Noble, 2004). Statistical analyses to explore relationships between variables included repeated-measures analysis of variance, regression analyses, independent-samples t tests, nonparametric Mann-Whitney tests, and correlations. Results In the simulated real-world environment, BCD group participants struggled with speech-in-noise understanding compared to control group participants. BCD benefit was observed for all microphone settings when speech stimuli were presented to the side with the BCD. When adaptive directional or fixed directional microphone settings were used, a relationship was noted between simulated real-world speech-in-noise performance for speech stimuli presented to the side with the BCD and subjective reports on the Background Noise subscale of the APHAB. Conclusions The Background Noise subscale of the APHAB may help estimate real-world speech-in-noise performance for BCD users with severe-to-profound UHL for signals of interest presented to the implanted side, specifically when adaptive or fixed directional microphone settings are used. This subscale may provide an efficient and accessible alternative to assessing real-world speech-in-noise performance in lieu of less clinically available measurement tools, such as an R-Space.

An Integrative Evaluation of the Efficacy of a Directional Microphone and Noise-Reduction Algorithm under Realistic Signal-to-Noise Ratios.

Many studies on the efficacy of directional microphones (DIRMs) and noise-reduction (NR) algorithms were not conducted under realistic signal-to-noise ratio (SNR) conditions. A Repeat-Recall Test (RRT) was developed previously to partially address this issue. This study evaluated whether the RRT could provide a more comprehensive understanding of the efficacy of a DIRM and NR algorithm under realistic SNRs. Possible interaction with listener working memory capacity (WMC) was assessed. This study uses a double-blind, within-subject repeated measures design. Nineteen listeners with a moderate degree of hearing loss participated. The RRT was administered with participants wearing the study hearing aids (HAs) under two microphones (omnidirectional versus directional) by two NR (on versus off) conditions. Speech was presented from 0° at 75 dB SPL and a continuous noise from 180° at SNRs of 0, 5, 10, and 15 dB. The order of SNR and HA conditions was counterbalanced across listeners. Each test condition was completed twice in two 2-hour sessions separated by one month. The recall scores of listeners were used to group listeners into good and poor WMC groups. Analysis using linear mixed-effects models revealed significant effects of context, SNR, and microphone for all four measures (repeat, recall, listening effort, and tolerable time). NR was only significant on the listening effort scale in the DIRM mode at an SNR of 5 dB. Listeners with good WMC performed better on all measures of the RRT and benefitted more from context. Although DIRM benefitted listeners with good and poor WMC, the benefits differed by context and SNR. The RRT confirmed the efficacy of DIRM and NR on several outcome measures under realistic SNRs. It also highlighted interactions between WMC and sentence context on feature efficacy.

Aplicación de la tecnología de enrutamiento inalámbrico contralateral de la señal (CROS) en usuarios de implante coclear unilateral

IntroductionSingle cochlear implantation usually provides substantial speech intelligibility benefits but bilaterally deaf, unilaterally implanted subjects will continue to experience limitations due to the head shadow effect, like single-sided deaf individuals. In the treatment of individuals with single-sided deafness one option is contralateral routing of signal (CROS) devices, which constitute a non-surgical intervention of the second ear in unilaterally implanted individuals. MethodTwelve experienced adult cochlear implant users with Naída Q70 processor and the CROS device used in combination participated in the study. For the study 3 conditions were provided: cochlear implant only, omnidirectional microphone mode (CROS deactivated); cochlear implant plus CROS activated, omnidirectional microphone mode and cochlear implant plus CROS activated, UltraZoom mode. Speech reception thresholds were determined in quiet and noise. Subjective feedback regarding the practical usability of the CROS device and the perceived benefit were collected. ResultsThere was a 27.6% improvement in speech understanding in quiet and 32.5% improvement in noise when CROS device was activated. Using advanced directional microphones, a statistically significant benefit of 35% was obtained. The responses to the questionnaires revealed that the subjects perceived benefit in their everyday lives when using the CROS device with their cochlear implants. ConclusionThe investigated CROS device used by unilateral CI recipients in cases where bilateral implantation is not an option provides both subjective and objective speech recognition benefit when the signal is directed to the CROS device. Unfavourable conditions where speech is presented from the cochlear implant side and noise from the CROS side or diffusely were not included in this evaluation since the CROS device adds additional noise and performance is expected to decrease as has previously been shown.

The efficacy of microphone directionality in improving speech recognition in noise for three commercial cochlear-implant systems

Objectives: To investigate the effect of fixed and adaptive microphone directionality on speech reception threshold (SRT) in noise when compared to omnidirectional mode in unilateral cochlear-implant (CI) use for three different CI systems.Methods: Twenty-four CI recipients with bilateral severe-to-profound hearing loss participated in the study. Eight recipients of each CI system were enrolled, and their SRT in noise was measured when the speech and noise signals were co-located in the front to serve as a baseline. The acute effect of different microphone directionalities on SRT in noise was measured with the noise emanating at 90° in the horizontal plane from the side of the CI sound processor (S0NCI).Results: When compared to the baseline condition, the individual data revealed fairly similar patterns within each CI system. In the S0NCI condition, the average improvement in SRT in noise for fixed and adaptive directionalities over the omnidirectional mode was statistically significant and ranged from 1.2 to 6.0 dB SNR and from 3.7 to 12.7 dB SNR depending on the CI system, respectively.Discussion: Directional microphones significantly improve SRT in noise for all three CI systems. However, relatively large differences were observed in the directional microphone efficacy between CI systems.

Evaluation of word recognition and word recall with bone conduction devices: do directional microphones free up cognitive resources?

Objective: To determine if directional microphones improve cognitive capacity in typically hearing adults. The study objectives are to evaluate differences in (1) speech recognition and (2) working memory through a word recall task between bilateral directional and omnidirectional microphone settings.Design: A conductive hearing loss was artificially induced while participants wore bilateral bone conduction hearing aids on softbands. For each hearing aid setting (bilateral omnidirectional and bilateral directional), seven blocks of seven sentences from the Hearing in Noise Test (HINT) were presented at a signal-to-noise ratio of +2 dB. Participants repeated each sentence aloud and after each block, wrote down as many of the last words as they could recall.Study sample: Thirty-five typical hearing adults and a subset (n = 20) achieving ≥80% recognition.Results: The directional microphone setting showed significant improvement over the omnidirectional setting for recognition and recall for both the full set of participants and the subset of participants with ≥ 80% recognition.Conclusions: This study demonstrated that features such as directional microphones can improve both speech recognition and working memory. Even in listening situations where participants can understand the majority of speech, directional microphones may offer improvements to cognitive capacity and reduce listening effort.

Effects of Omnidirectional Microphone Placement and Survey Period on Bat Echolocation Call Quality and Detection Probabilities

Many factors, including microphone type, affect the quality of acoustic calls recorded by bat detectors and detection probabilities of individual species. Because omnidirectional microphones tend to have a shorter range and record more noise than directional microphones, it has been suggested that these microphones be set farther from reflecting surfaces. Our objective was to determine the effects of microphone height (1.5, 5, and 9 m), distance from forest edge (1, 3, and 5 m), and survey timing on the number of bat files recorded, quality of recorded files, the proportion of identifiable files, and the probability of detecting individual species. We deployed 3×3 arrays of two types of bat detectors with omnidirectional microphones at two sites in Kentucky during two survey periods. We found little evidence for effects of microphone height or distance from forest edge on call quality or detection probabilities of any species. In contrast, survey period significantly affected the number of files recorded, the proportion of high-quality files, the proportion of identifiable files, and the probability of detecting individual species; the length of the recording session also significantly affected the probability of detecting some species. Thus, it appears that biologists have some latitude when placing detectors with omnidirectional microphones on the landscape but timing of surveys should be considered when designing and analyzing bat acoustic survey and monitoring studies.

Audiological outcome measures with the BONEBRIDGE transcutaneous bone conduction hearing implant: impact of noise, reverberation and signal processing features

Objective: To assess the performance of an active transcutaneous implantable-bone conduction device (TI-BCD), and to evaluate the benefit of device digital signal processing (DSP) features in challenging listening environments.Design: Participants were tested at 1- and 3-month post-activation of the TI-BCD. At each session, aided and unaided phoneme perception was assessed using the Ling-6 test. Speech reception thresholds (SRTs) and quality ratings of speech and music samples were collected in noisy and reverberant environments, with and without the DSP features. Self-assessment of the device performance was obtained using the Abbreviated Profile of Hearing Aid Benefit (APHAB) questionnaire.Study sample: Six adults with conductive or mixed hearing loss.Results: Average SRTs were 2.9 and 12.3 dB in low and high reverberation environments, respectively, which improved to −1.7 and 8.7 dB, respectively with the DSP features. In addition, speech quality ratings improved by 23 points with the DSP features when averaged across all environmental conditions. Improvement scores on APHAB scales revealed a statistically significant aided benefit.Conclusions: Noise and reverberation significantly impacted speech recognition performance and perceived sound quality. DSP features (directional microphone processing and adaptive noise reduction) significantly enhanced subjects’ performance in these challenging listening environments.

Effect of Directional Microphone Technology in Hearing Aids on Neural Correlates of Listening and Memory Effort: An Electroencephalographic Study.

The aim of the study was to compare the effect of different spatial noise-processing algorithms in hearing aids on listening effort and memory effort on a subjective, behavioral, and neurophysiological level using electroencephalography (EEG). Two types of directional microphone (DM) technologies for spatial noise processing were chosen: one with a wide directionality (wide DM) and another with a narrower directionality (narrow DM) to accentuate the speech source. Participants with a severe hearing loss were fitted with hearing aids and participated in two EEG experiments. In the first one, participants listened to sentences in cafeteria noise and were asked to rate the experienced listening effort. The second EEG experiment was a listening span task during which participants had to repeat sentence material and then recall the final words of the last four sentences. Subjective listening effort was lower with narrow than wide DM and EEG alpha power was reduced for the narrow DM. The results of the listening span task indicated a reduction in experienced memory effort and better memory performance. During the memory retention phase, EEG alpha level for the narrow relative to the wide DM was reduced. This effect was more pronounced during linguistically difficult sentences. This study extends previous findings, as it reveals a benefit for narrow DM in terms of cognitive performance and memory effort also on a neural level, and when speech intelligibility is almost 100%. Together, this indicates that a narrow and focused DM allows for a more efficient neurocognitive processing than a wide DM.

Improving Cochlear Implant Performance in the Wind Through Spectral Masking Release: A Multi-microphone and Multichannel Strategy.

Adopting the omnidirectional microphone (OMNI) mode and reducing low-frequency gain are the two most commonly used wind noise reduction strategies in hearing devices. The objective of this study was to compare the effectiveness of these two strategies on cochlear implant users' speech-understanding abilities and perceived sound quality in wind noise. We also examined the effectiveness of a new strategy that adopts the microphone mode with lower wind noise level in each frequency channel. A behind-the-ear digital hearing aid with multiple microphone modes was used to record testing materials for cochlear implant participants. It was adjusted to have linear amplification, flat frequency response when worn on a Knowles Electronic Manikin for Acoustic Research to remove the head-related transfer function of the manikin and to mimic typical microphone characteristics of hearing devices. Recordings of wind noise samples and hearing-in-noise test sentences were made when the hearing aid was programmed to four microphone modes, namely (1) OMNI; (2) adaptive directional microphone (ADM); (3) ADM with low-frequency roll-off; and (4) a combination of omnidirectional and directional microphone (COMBO). Wind noise samples were recorded in an acoustically treated wind tunnel from 0° to 360° in 10° increment at a wind velocity of 4.5, 9.0, and 13.5 m/s when the hearing aid was worn on the manikin. Two wind noise samples recorded at 90° and 300° head angles at the wind velocity of 9.0 m/s were chosen to take advantage of the spectral masking release effects of COMBO. The samples were then mixed with the sentences recorded using identical settings. Cochlear implant participants listened to the speech-in-wind testing materials and they repeated the sentences and compared overall sound quality preferences of different microphone modes using a paired-comparison categorical rating paradigm. The participants also rated their preferences of wind-only samples. COMBO yielded the highest speech recognition scores among the four microphone modes, and it was also preferred the most often, likely due to the reduction of spectral masking. The speech recognition scores generated using ADM with low-frequency roll-off were either equal to or lower than those obtained using ADM because gain reduction decreased not only the level of wind noise but also the low-frequency energy of speech. OMNI consistently yielded speech recognition scores lower than COMBO, and it was often rated as less preferable than other microphone modes, suggesting the conventional strategy to switch to the omnidirectional mode in the wind was undesirable. Neither adopting an OMNI nor reducing low-frequency gain generated higher speech recognition scores or higher sound quality ratings than COMBO. Adopting the microphone with lower wind noise level in different frequency channels can provide spectral masking release, and it is a more effective wind noise reduction strategy. The natural 6 dB/octave low-frequency roll-off of first-order directional microphones should be compensated when speech is present. Signal detection and decision rules for wind noise reduction applications are discussed in hearing devices with and without binaural transmission capability.

Usefulness of Hammering Sound Frequency Analysis as an Evaluation Method for the Prevention of Trouble during Hip Replacement

In total hip arthroplasty, judgment of the appropriateness of stem hammering is dependent on the experience and feelings of the surgeon and no objective evaluation method has been established. In this study, a frequency analysis of the hammering sounds in total hip arthroplasty was performed to investigate objective judgment criteria capable of preventing problems during surgery. Stem hammering was applied following the surgeon’s feelings as usual in an operating room. A directional microphone was placed at a distance about 2 m from the surgical field and the peak frequency reaching the maximum amplitude was determined by Fourier analysis. It was clarified that the same peak frequency repeats when appropriate fixation is acquired during surgery, suggesting that intraoperative fracture and postoperative loosening can be prevented by stopping hammering at the time the peak frequency converged. Investigation of changes in the hammering sound frequency may serve as objective judgment criteria capable of preventing problems during surgery.

Effect of Microphone Location and Beamforming Technology on Speech Recognition in Pediatric Cochlear Implant Recipients

Background: Despite improvements in cochlear implant (CI) technology, pediatric CI recipients continueto have more difficulty understanding speech than their typically hearing peers in background noise. Avariety of strategies have been evaluated to help mitigate this disparity, such as signal processing, remotemicrophone technology, and microphone placement. Previous studies regarding microphoneplacement used speech processors that are now dated, and most studies investigating the improvementof speech recognition in background noise included adult listeners only.Purpose: The purpose of the present study was to investigate the effects of microphone location andbeamforming technology on speech understanding for pediatric CI recipients in noise.Research Design: A prospective, repeated-measures, within-participant design was used to compareperformance across listening conditions.Study Sample: A total of nine children (aged 6.6 to 15.3 years) with at least one Advanced Bionics CIwere recruited for this study.Data Collection and Analysis: The Basic English Lexicon Sentences and AzBio Sentences were presentedat 0° azimuth at 65-dB SPL in +5 signal-to-noise ratio noise presented from seven speakers usingthe R-SPACE system (Advanced Bionics, Valencia, CA). Performance was compared across three omnidirectionalmicrophone configurations (processor microphone, T-Mic 2, and processor + T-Mic 2) andtwo directional microphone configurations (UltraZoom and auto UltraZoom). The two youngest participantswere not tested in the directional microphone configurations.Results: No significant differences were found between the various omnidirectional microphone configurations.UltraZoom provided significant benefit over all omnidirectional microphone configurations(T-Mic 2, p = 0.004, processor microphone, p &lt; 0.001, and processor microphone + T-Mic 2, p = 0.018)but was not significantly different from auto UltraZoom (p = 0.176).Conclusions: All omnidirectional microphone configurations yielded similar performance, suggesting thata child’s listening performance in noise will not be compromised by choosing the microphone configurationbest suited for the child. UltraZoom (adaptive beamformer) yielded higher performance than all omnidirectional microphonesin moderate background noise for adolescents aged 9 to 15 years. The implicationsof these data suggest that for older children who are able to reliably use manual controls, UltraZoom willyield significantly higher performance in background noise when the target is in front of the listener.