Coalition for Global Hearing Health Hearing Care Pathways Working Group: Guidelines for Clinical Guidance for Readiness and Development of Evidence-Based Early Hearing Detection and Intervention Programs.

Editor's Note: The following article discusses the timely topic Clinical Guidance in the areas of Evidence-Based Early Hearing Detection and Intervention Programs. This article aims to discuss areas of services needed, guidance to countries/organizations attempting to initiate early hearing detection and intervention systems. Expert consensus and systematic/scoping reviews were combined to produce recommendations for evidence-based clinical practice. In Ear and Hearing, our long-term goal for the Point of View article is to stimulate the field's interest in and to enhance the appreciation of the author's area of expertise. Hearing is an important sense for children to develop cognitive, speech, language, and psychosocial skills. The goal of universal newborn hearing screening is to enable the detection of hearing loss in infants so that timely health and educational/therapeutic intervention can be provided as early as possible to improve outcomes. While many countries have implemented universal newborn hearing screening programs, many others are yet to start. As hearing screening is only the first step to identify children with hearing loss, many follow-up services are needed to help them thrive. However, not all of these services are universally available, even in high-income countries. The purposes of this article are (1) to discuss the areas of services needed in an integrated care system to support children with hearing loss and their families; (2) to provide guidance to countries/organizations attempting to initiate early hearing detection and intervention systems with the goal of meeting measurable benchmarks to assure quality; and (3) to help established programs expand and improve their services to support children with hearing loss to develop their full potential. Multiple databases were interrogated including PubMed, Medline (OVIDSP), Cochrane library, Google Scholar, Web of Science and One Search, ERIC, PsychInfo. Expert consensus and systematic/scoping reviews were combined to produce recommendations for evidence-based clinical practice. Eight essential areas were identified to be central to the integrated care: (1) hearing screening, (2) audiologic diagnosis and management, (3) amplification, (4) medical evaluation and management, (5) early intervention services, (6) family-to-family support, (7) D/deaf/hard of hearing leadership, and (8) data management. Checklists are provided to support the assessment of a country/organization's readiness and development in each area as well as to suggest alternative strategies for situations with limited resources. A three-tiered system (i.e., Basic, Intermediate, and Advanced) is proposed to help countries/organizations at all resource levels assess their readiness to provide the needed services and to improve their integrated care system. Future directions and policy implications are also discussed.

Hearing Aid Loan Program for Hearing Loss at the End of Life.

This article describes a hearing aid loan program to provide free amplification devices for patients at the end of life to help them communicate more effectively at this critical time. It includes steps for establishing such a program, addressing challenges, and the role of the informal caregiver throughout the intervention. Healthcare professionals and social workers are encouraged to develop similar programs and use the information here as helpful suggestions to consider for their programs.

Severity of gastric intestinal metaplasia predicts the risk of gastric cancer: a prospective multicentre cohort study (GCEP).

OBJECTIVE: To investigate the incidence of gastric cancer (GC) attributed to gastric intestinal metaplasia (IM), and validate the Operative Link on Gastric Intestinal Metaplasia (OLGIM) for targeted endoscopic surveillance in regions with low-intermediate incidence of GC. METHODS: A prospective, longitudinal and multicentre study was carried out in Singapore. The study participants comprised 2980 patients undergoing screening gastroscopy with standardised gastric mucosal sampling, from January 2004 and December 2010, with scheduled surveillance endoscopies at year 3 and 5. Participants were also matched against the National Registry of Diseases Office for missed diagnoses of early gastric neoplasia (EGN). RESULTS: There were 21 participants diagnosed with EGN. IM was a significant risk factor for EGN (adjusted-HR 5.36; 95% CI 1.51 to 19.0; p<0.01). The age-adjusted EGN incidence rates for patients with and without IM were 133.9 and 12.5 per 100 000 person-years. Participants with OLGIM stages III-IV were at greatest risk (adjusted-HR 20.7; 95% CI 5.04 to 85.6; p<0.01). More than half of the EGNs (n=4/7) attributed to baseline OLGIM III-IV developed within 2 years (range: 12.7-44.8 months). Serum trefoil factor 3 distinguishes (Area Under the Receiver Operating Characteristics 0.749) patients with OLGIM III-IV if they are negative for H. pylori. Participants with OLGIM II were also at significant risk of EGN (adjusted-HR 7.34; 95% CI 1.60 to 33.7; p=0.02). A significant smoking history further increases the risk of EGN among patients with OLGIM stages II-IV. CONCLUSIONS: We suggest a risk-stratified approach and recommend that high-risk patients (OLGIM III-IV) have endoscopic surveillance in 2 years, intermediate-risk patients (OLGIM II) in 5 years.

Development and validation of a serum microRNA biomarker panel for detecting gastric cancer in a high-risk population.

OBJECTIVE: An unmet need exists for a non-invasive biomarker assay to aid gastric cancer diagnosis. We aimed to develop a serum microRNA (miRNA) panel for identifying patients with all stages of gastric cancer from a high-risk population. DESIGN: We conducted a three-phase, multicentre study comprising 5248 subjects from Singapore and Korea. Biomarker discovery and verification phases were done through comprehensive serum miRNA profiling and multivariant analysis of 578 miRNA candidates in retrospective cohorts of 682 subjects. A clinical assay was developed and validated in a prospective cohort of 4566 symptomatic subjects who underwent endoscopy. Assay performance was confirmed with histological diagnosis and compared with Helicobacter pylori (HP) serology, serum pepsinogens (PGs), 'ABC' method, carcinoembryonic antigen (CEA) and cancer antigen 19-9 (CA19-9). Cost-effectiveness was analysed using a Markov decision model. RESULTS: We developed a clinical assay for detection of gastric cancer based on a 12-miRNA biomarker panel. The 12-miRNA panel had area under the curve (AUC)=0.93 (95% CI 0.90 to 0.95) and AUC=0.92 (95% CI 0.88 to 0.96) in the discovery and verification cohorts, respectively. In the prospective study, overall sensitivity was 87.0% (95% CI 79.4% to 92.5%) at specificity of 68.4% (95% CI 67.0% to 69.8%). AUC was 0.848 (95% CI 0.81 to 0.88), higher than HP serology (0.635), PG 1/2 ratio (0.641), PG index (0.576), ABC method (0.647), CEA (0.576) and CA19-9 (0.595). The number needed to screen is 489 annually. It is cost-effective for mass screening relative to current practice (incremental cost-effectiveness ratio=US$44 531/quality-of-life year). CONCLUSION: We developed and validated a serum 12-miRNA biomarker assay, which may be a cost-effective risk assessment for gastric cancer. TRIAL REGISTRATION NUMBER: This study is registered with ClinicalTrials.gov (Registration number: NCT04329299).

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

OBJECTIVES: 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. DESIGN: 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. RESULTS: 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. CONCLUSIONS: 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.

Detection of hearing problems in Aboriginal and Torres strait islander children: a comparison between clinician-administered and self-administrated hearing tests.

Objective: This study evaluated the agreement of self-administered tests with clinician-administered tests in detecting hearing loss and speech-in-noise deficits in Aboriginal & Torres Strait Islander children.Design: Children completed clinician-administered audiometry, self-administered automatic audiometry (AutoAud), clinician-administered Listening in Spatialised Noise - Sentences test and self-administered tablet-based hearing game Sound Scouts. Comparisons were made between tests to determine the agreement of the self-administered tests with clinician-administered tests in detecting hearing loss and speech-in-noise deficits.Study sample: Two hundred and ninety seven Aboriginal and Torres Strait Islander children aged 4-14 years from three schools.Results: Acceptable threshold differences of ≤5 dB between AutoAud and manual audiometry hearing thresholds were found for 88% of thresholds, with a greater agreement for older than for younger children. Consistent pass/fail results on the Sound Scouts speech-in-quiet measure and manual audiometry were found for 81% of children. Consistent pass/fail results on the Sound Scouts speech-in-noise measure and LiSN-S high-cue condition were found for 73% of children.Conclusions: This study shows good potential in using self-administered applications as initial tests for hearing problems in children. These tools may be especially valuable for children in remote locations and those from low socio-economic backgrounds who may not have easy access to healthcare.

A Systematic Review of the Literature of Delayed Inflammatory Reactions After Hyaluronic Acid Filler Injection to Estimate the Incidence of Delayed Type Hypersensitivity Reaction.

BACKGROUND: Hyaluronic acid (HA) dermal filler injection is believed to be a safe procedure. However, with the increase in the number of performed procedures and indications, the number of product-related complications, especially delayed inflammatory reactions, has also increased. Delayed-type hypersensitivity (DTH) reaction is one of these delayed inflammatory reactions, which is preventable by performing a pretreatment skin test. OBJECTIVES: The authors sought to find the incidence of delayed inflammatory reactions and DTH reaction after HA injection and to determine whether a pretreatment skin test is worthwhile to be performed. METHODS: The authors conducted a systematic literature review of all the relevant prospective studies, retrospective studies, and case reports on delayed inflammatory reactions and DTH reaction after HA filler injection. RESULTS: The incidence of delayed inflammatory reactions calculated from the prospective studies was 1.1% per year, and that of possible DTH reaction was 0.06% per year. Most retrospective studies estimated a percentage of delayed inflammatory reactions of less than 1% in 1 to 5.5 years. The incidence of DTH reaction would be lower than that. Among all the DTH cases reported, only about 5% of them were proven to be genuine DTH reactions. CONCLUSIONS: The incidence of both delayed inflammatory reactions and DTH reaction is low. There is evidence that genuine DTH reactions caused by HA fillers approved by the Food and Drug Administration do exist. This adverse event can be prevented by performing a pretreatment skin test. However, the incidence of DTH reaction is so low that the pretreatment skin test is not mandatory if Food and Drug Administration-approved HA fillers are used.

An observational study of temperature and thermal images of surgical wounds for detecting delayed wound healing within four days after surgery.

AIM: To elucidate the infrared thermal patterns and temperature readings of the surfaces of surgical wounds for detecting delayed wound healing within four days after surgery. BACKGROUND: The nursing assessment of surgical wounds within the first four days after surgery is commonly based on visual and physical examination. Surgical wounds with delayed healing may be not detected if they do not exhibit signs such as redness or exudate within four days after surgery. DESIGN: This study was conducted using prospective observational design with reference to the STROBE Statement (see Supporting Information Appendix S1) to examine the temperatures of surgical wounds in their natural settings. METHODS: Based on convenience sampling, 60 participants admitted to the colorectal surgical ward for enterostoma closure from January-November 2013 were recruited. RESULTS: Although both infected and noninfected surgical wounds exhibited a significant increase in wound temperature from Days 1-4, the infected wounds revealed a statistically significantly lower temperature than the noninfected ones. Within the infrared thermal images, the infected wounds presented with partial warming of the skin surrounding and along the incision, suggesting that delayed healing could be identified. CONCLUSION: This study demonstrates that delayed wound healing can be detected within the first four days after surgery for early intervention of prevention and treatment before discharge. RELEVANCE TO CLINICAL PRACTICE: This paper provides evidence-based information for healthcare professionals in assessing surgical wounds for delayed healing within the first four days after surgery. The findings herein enable the early detection of delayed wound healing, based on which early intervention of prevention and treatment may be instituted for affected patients before their discharge.

Inhibition of class I histone deacetylases by romidepsin potently induces Epstein-Barr virus lytic cycle and mediates enhanced cell death with ganciclovir.

Pan-histone deacetylase (HDAC) inhibitors, which inhibit 11 HDAC isoforms, are widely used to induce Epstein-Barr virus (EBV) lytic cycle in EBV-associated cancers in vitro and in clinical trials. Here, we hypothesized that inhibition of one or several specific HDAC isoforms by selective HDAC inhibitors could potently induce EBV lytic cycle in EBV-associated malignancies such as nasopharyngeal carcinoma (NPC) and gastric carcinoma (GC). We found that inhibition of class I HDACs, particularly HDAC-1, -2 and -3, was sufficient to induce EBV lytic cycle in NPC and GC cells in vitro and in vivo. Among a panel of selective HDAC inhibitors, the FDA-approved HDAC inhibitor romidepsin was found to be the most potent lytic inducer, which could activate EBV lytic cycle at ∼0.5 to 5 nM (versus ∼800 nM achievable concentration in patients' plasma) in more than 75% of cells. Upregulation of p21(WAF1) , which is negatively regulated by class I HDACs, was observed before the induction of EBV lytic cycle. The upregulation of p21(WAF1) and induction of lytic cycle were abrogated by a specific inhibitor of PKC-δ but not the inhibitors of PI3K, MEK, p38 MAPK, JNK or ATM pathways. Interestingly, inhibition of HDAC-1, -2 and -3 by romidepsin or shRNA knockdown could confer susceptibility of EBV-positive epithelial cells to the treatment with ganciclovir (GCV). In conclusion, we demonstrated that inhibition of class I HDACs by romidepsin could potently induce EBV lytic cycle and mediate enhanced cell death with GCV, suggesting potential application of romidepsin for the treatment of EBV-associated cancers.

Azo dyes and human health: A review.

Synthetic azo dyes are widely used in industries. Gerhardt Domagk discovered that the antimicrobial effect of red azo dye Prontosil was caused by the reductively cleaved (azo reduction) product sulfanilamide. The significance of azo reduction is thus revealed. Azo reduction can be accomplished by human intestinal microflora, skin microflora, environmental microorganisms, to a lesser extent by human liver azoreductase, and by nonbiological means. Some azo dyes can be carcinogenic without being cleaved into aromatic amines. However, the carcinogenicity of many azo dyes is due to their cleaved product such as benzidine. Benzidine induces various human and animal tumors. Another azo dye component, p-phenylenediamine, is a contact allergen. Many azo dyes and their reductively cleaved products as well as chemically related aromatic amines are reported to affect human health, causing allergies and other human maladies.

Smart-Adhesive, Breathable and Waterproof Fibrous Electronic Skins.

For the need of direct contact with the skin, electronic skins (E-skins) should not only fulfill electric functions, but also ensure comfort during wearing, including permeability, waterproofness, and easy removal. Herein, the study has developed a self-adhesive, detach-on-demand, breathable, and waterproof E-skin (PDSC) for motion sensing and wearable comfort by electrospinning styrene-isoprene block copolymer rubber with carbon black nanosheets as the sensing layer and liner copolymers of N, N-dimethylacrylamide, n-octadecyl acrylate and lauryl methacrylate as the adhesive layer. The high elasticity and microfiber network structure endow the PDSC with good sensitivity and high linearity for strain sensing. The hydrophobic and crystallizable adhesive layer ensures robust, waterproof, and detaching-on-demand skin adhesion. Meanwhile, the fiber structure enables the PDSC good air and water permeability. The integration of electric and wearable functions endows the PDSC with great potential for motion sensing during human activities as both the sensing and wearable performances.

Naturally Crosslinked Biocompatible Carbonaceous Liquid Metal Aqueous Ink Printing Wearable Electronics for Multi-Sensing and Energy Harvesting.

Achieving flexible electronics with comfort and durability comparable to traditional textiles is one of the ultimate pursuits of smart wearables. Ink printing is desirable for e-textile development using a simple and inexpensive process. However, fabricating high-performance atop textiles with good dispersity, stability, biocompatibility, and wearability for high-resolution, large-scale manufacturing, and practical applications has remained challenging. Here, water-based multi-walled carbon nanotubes (MWCNTs)-decorated liquid metal (LM) inks are proposed with carbonaceous gallium-indium micro-nanostructure. With the assistance of biopolymers, the sodium alginate-encapsulated LM droplets contain high carboxyl groups which non-covalently crosslink with silk sericin-mediated MWCNTs. E-textile can be prepared subsequently via printing technique and natural waterproof triboelectric coating, enabling good flexibility, hydrophilicity, breathability, wearability, biocompatibility, conductivity, stability, and excellent versatility, without any artificial chemicals. The obtained e-textile can be used in various applications with designable patterns and circuits. Multi-sensing applications of recognizing complex human motions, breathing, phonation, and pressure distribution are demonstrated with repeatable and reliable signals. Self-powered and energy-harvesting capabilities are also presented by driving electronic devices and lighting LEDs. As proof of concept, this work provides new opportunities in a scalable and sustainable way to develop novel wearable electronics and smart clothing for future commercial applications.

Effects of venting on wind noise levels measured at the eardrum.

OBJECTIVES: Wind noise can be a nuisance to hearing aid users. With the advent of sophisticated feedback reduction algorithms, people with higher degrees of hearing loss are fit with larger vents than previously allowed, and more people with lesser degrees of hearing loss are fit with open hearing aids. The purpose of this study was to examine the effects of venting on wind noise levels in the ear canal for hearing aids with omnidirectional and directional microphones. DESIGN: Two behind-the-ear hearing aids were programmed when they were worn on a Knowles Electronics Manikin for Acoustic Research. The hearing aid worn on the right ear was programmed to the omnidirectional microphone mode and the one on the left to the directional microphone mode. The hearing aids were adjusted to linear amplification with flat frequency response in an anechoic chamber. Gains below 10 dB were used to avoid output limiting of wind noise levels at low input levels. Wind noise samples were recorded at the eardrum location in a wind tunnel at wind velocities ranging from a gentle to a strong breeze. The hearing aids were coupled to #13 tubings (i.e., open vent), or conventional skeleton earmolds with no vent, pressure vents, or 3mm vents. Polar and spectral characteristics of wind noise were analyzed off-line using MatLab programs. RESULTS: Wind noise levels in the ear canals were mostly predicted by vent-induced frequency response changes in the conventional earmold conditions for both omnidirectional and directional hearing aids. The open vent condition, however, yielded the lowest levels, which could not be entirely predicted by the frequency response changes of the hearing aids. This indicated that a wind-related vent effect permitted an additional amount of sound reduction in the ear canal, which could not be explained by known vent effects. CONCLUSION: For the microphone location, form factor, and gain settings tested, open fit hearing aids yielded lower noise levels at the eardrum location than conventional behind-the-ear hearing aids.

Relationship between road traffic noisescape and urban form in Hong Kong.

This paper reports on a study which explored the possible relationship between road traffic noisescape and urban form in Hong Kong. A total of 212 residential complexes from 11 contrasting urban forms were sampled, and their noise levels assessed both at dwelling and neighbourhood scales by noise mapping. Its findings indicate that residential complexes with different urban forms have significantly different noisescape attributes. There is a strong correlation between the noise characteristics and morphological indicators at the dwelling scale. A less obstreperous noisescape is associated with urban forms with lower road and building densities, and with building arrangements which provide self-noise screening. These findings suggest that urban form is an influential determinant of the noisescape in the urban environment, and they point to the need to rethink the conventional approach to managing the urban acoustic environment.

Alternative audiometric calibration methods: Evaluation of sound level measuring apps for audiometric calibration.

Audiometric calibration, which includes the calibration of different audiometer transducers and the measurements of ambient noise levels, is historically carried out using Class 1 sound level meters. As technologies advance, many mobile applications (apps) have been developed to measure sound levels. These apps can provide alternative methods for audiometric calibration in places where sound level meters are not available, such as field testing environments, low-to-mid-income countries, and humanitarian settings. These apps, however, cannot be used for audiometric calibration without first evaluating their performance, which depends on multiple factors including the external components (if any), the operating system and the hardware of the electronic devices. The evaluation of the apps is actually the evaluation of the app and associated factors (i.e., the app systems). This paper discusses methods to assess several key functions of apps implemented in either Android or iOS operation system for audiometric calibration: 1) checking the measurement accuracy at all testing frequencies, 2) deriving and using correction factors, 3) determining the self-noise levels, and 4) evaluating the linear/measurement range. As audiometric calibration usually uses octave or 1/3 octave bands to measure sound pressure levels of tones and narrowband noises with relatively steady temporal characteristics, the accuracy of an app can be evaluated by comparing the levels measured by the app and a Class 1 sound level meter at each frequency. The level difference between the app and the Class 1 sound level meter at each frequency can then be used to calculate correction factors that can be added to subsequent levels measured by the app to improve its accuracy. In addition, methods to determine the self-noise level and the linearity range of apps are discussed. Sample measurement scenarios and alternative methods are provided to illustrate the evaluation process to determine whether an app is suitable for measuring ambient noise levels and for calibrating different audiometric transducers.

Calibration matters: II. Measurement of ambient noise in test rooms/areas.

Ambient noise measurement is a part of audiometric calibration in which one measures the ambient noise level in a sound room/test area intended for audiometric testing and then decides whether the background noise in the test room meets the maximum permissible ambient noise level (MPANL) requirements specified in national or international standards, e.g., ANSI/ASA S3.1:1999(R2018) or ISO 8253-1:2010 (R2021). If the ambient noise levels are below the MPANLs, clinicians can be sure that the test stimuli they present to patients are not masked by the background noise in the test room/area and their test results are valid and the subsequent clinical decisions are sound. Audiometric testing, however, may not always be carried out in sound rooms/test areas with ambient noise levels below the MPANLs, especially during community outreach or humanitarian services. A thorough understanding on the MPANL requirements for different transducers can help clinicians determine which equipment is appropriate for the test area. This tutorial discusses the rationale and assumptions behind the MPANL specifications, how to measure ambient noise levels of test rooms/areas, and how to apply the national and international standards to determine if the test room is suitable for audiometric testing. Alternative strategies are discussed when the ambient noise levels exceed the specified MPANLs. The rationale and procedures are explained using examples on how to lower the ambient noise levels in test areas, and how to determine the suitable test frequency range and the lowest threshold levels that can be assessed in the test area.

Calibration matters: I. Sound level meter basics.

Calibration is an essential component of audiology practice to ensure the accuracy of the equipment for audiometric tests and the transferability of test results across different clinics and countries. The ability to check the accuracy of the equipment and the ambient noise levels allows clinicians to monitor the functions of their equipment, to reduce noise distractors in the testing environment, and to have confidence in their test results, especially in humanitarian or field test settings. Sound level meters are the primary instruments to measure the sound pressure levels of the transducers and the test rooms used for audiometric testing. The International Electrotechnical Commission released a 3-part IEC 61672 standard of the specifications of sound level meters in 2013, and it is adopted by the standards organizations of many countries. This first installment of the tutorial series references this international standard and discusses basic acoustics concepts, calibration principles, and key functions of sound level meters in the application of audiometric calibration. Subsequent installments will discuss how to measure the ambient noise levels, how to determine whether a test room is suitable for testing hearing thresholds using different transducers, and how to determine whether different transducers of audiometers meet the national or international standards.

Comparisons of spectral characteristics of wind noise between omnidirectional and directional microphones.

Wind noise reduction is a topic of ongoing research and development for hearing aids and cochlear implants. The purposes of this study were to examine spectral characteristics of wind noise generated by directional (DIR) and omnidirectional (OMNI) microphones on different styles of hearing aids and to derive wind noise reduction strategies. Three digital hearing aids (BTE, ITE, and ITC) were fitted to Knowles Electronic Manikin for Acoustic Research. They were programmed to have linear amplification and matching frequency responses between the DIR and OMNI modes. Flow noise recordings were made from 0° to 360° azimuths at flow velocities of 4.5, 9.0, and 13.5 m/s in a quiet wind tunnel. Noise levels were analyzed in one-third octave bands from 100 to 8000 Hz. Comparison of wind noise revealed that DIR generally produced higher noise levels than OMNI for all hearing aids, but it could result in lower levels than OMNI at some frequencies and head angles. Wind noise reduction algorithms can be designed to detect noise levels of DIR and OMNI outputs in each frequency channel, remove the constraint to switch to OMNI in low-frequency channel(s) only, and adopt the microphone mode with lower noise levels to take advantage of the microphone differences.

Wind noise in hearing aids: I. Effect of wide dynamic range compression and modulation-based noise reduction.

OBJECTIVE: The objectives of this study were: (1) to examine the effect of wide dynamic range compression (WDRC) and modulation-based noise reduction (NR) algorithms on wind noise levels at the hearing aid output; and (2) to derive effective strategies for clinicians and engineers to reduce wind noise in hearing aids. DESIGN: Three digital hearing aids were fitted to KEMAR. The noise output was recorded at flow velocities of 0, 4.5, 9.0, and 13.5 m/s in a wind tunnel as the KEMAR head was turned from 0° to 360°. STUDY SAMPLE: Flow noise levels were compared between the 1:1 linear and 3:1 WDRC conditions, and between NR-activated and NR-deactivated conditions when the hearing aid was programmed to the directional and omnidirectional modes. RESULTS: The results showed that: (1) WDRC increased low-level noise and reduced high-level noise; and (2) different noise reduction algorithms provided different amounts of wind noise reduction in different microphone modes, frequency regions, flow velocities, and head angles. CONCLUSIONS: Wind noise can be reduced by decreasing the gain for low-level inputs, increasing the compression ratio for high-level inputs, and activating modulation-based noise reduction algorithms.

Wind noise in hearing aids: II. Effect of microphone directivity.

OBJECTIVES: The objectives were: (1) to examine the effects of a directional microphone with different directivity patterns and different microphone combinations on wind noise levels at the hearing aid output; and (2) to derive strategies appropriate for hearing aid selection and future designs. DESIGN: The in-situ frequency responses of a behind-the-ear hearing aid (BTE1) were matched when the hearing aid was programmed to dipole, hypercardioid, cardioids, or adaptive microphone mode. The in-situ frequency responses of another hearing aid (BTE2) were matched among an omnidirectional microphone (OMNI), an adaptive directional microphone (ADM), and a combination of an omnidirectional microphone at low frequencies and an adaptive directional microphone at high frequencies (MIXED). Flow noise was recorded at flow velocities of 0, 4.5, 9.0, and 13.5 m/s. Measurements were repeated for the hypercardioid pattern of BTE1. STUDY SAMPLE: Flow noise recorded using directional microphones with four directivity patterns and using OMNI, ADM, and MIXED. RESULTS: Directional microphones with different directivity patterns generated similar flow noise levels. ADM yielded higher overall levels than OMNI and MIXED, which had similar overall levels. CONCLUSIONS: The adaptive directional microphone is the most versatile microphone for use in wind. The mixed microphone mode is a viable wind noise reduction option.