Hearing Capacity Research Articles

Assessment Of Ambient-Noise Exposure Among Female Nurses In Surgical Cardiac Intensive Care Unit.

PurposeTo measure noise levels in the Saud Albabtain Cardiac Center cardiac surgical intensive-care unit (CSICU) at different locations to find out the prevalence of noise-induced hearing loss among female nurses.MethodsAmbient CSICU noise was measured using a sound-level meter and personal noise dosimeter during morning and night shifts (12 hours each) for 30 days. An audiometry test and questionnaire were used to test nursing responses to noise levels.ResultsMean 12-hour average noise levels at the station during night shift were 60.3±7.1 dB(A) and inside rooms 62.48±8.02 dB(A). However, during morning shift 64.1±8.4 dB(A) in the rooms was recorded, while 68.8±8.2 dB(A) was recorded at the station, with a significant difference between the shifts (p<0.0001). ICU monitors recorded the highest noise-source levels of 82.7±5.3 dB(A). The lowest significant source was the suction machines, with an average of 67.1±12.5 dB(A). A significant correlation between decibel loss and nurse experience was observed.ConclusionNoise levels in the CSICU at Saud Albabtain Cardiac Center were higher than World Health Organization standards. CSICU nurses are exposed to noise levels that can affect their hearing capacity. Further research isneeded for effective medical device–alarm management.

Sound sequences in birdsong: how much do birds really care?

The complex and melodic nature of many birds' songs has raised interest in potential parallels between avian vocal sequences and human speech. The similarities between birdsong and speech in production and learning are well established, but surprisingly little is known about how birds perceive song sequences. One popular laboratory songbird, the zebra finch (Taeniopygia guttata), has recently attracted attention as an avian model for human speech, in part because the male learns to produce the individual elements in its song motif in a fixed sequence. But psychoacoustic evidence shows that adult zebra finches are relatively insensitive to the sequential features of song syllables. Instead, zebra finches and other birds seem to be exquisitely sensitive to the acoustic details of individual syllables to a degree that is beyond human hearing capacity. Based on these findings, we present a finite-state model of zebra finch perception of song syllable sequences and discuss the rich informational capacity of their vocal system. Furthermore, we highlight the abilities of budgerigars (Melopsittacus undulatus), a parrot species, to hear sequential features better than zebra finches and suggest that neurophysiological investigations comparing these species could prove fruitful for uncovering neural mechanisms for auditory sequence perception in human speech. This article is part of the theme issue 'What can animal communication teach us about human language?'

Characteristic of Stimulus Frequency Otoacoustic Emissions: Detection Rate, Musical Training Influence, and Gain Function.

Stimulus frequency otoacoustic emission (SFOAE) is an active acoustic signal emitted by the inner ear providing salient information about cochlear function and dysfunction. To provide a basis for laboratory investigation and clinical use, we investigated the characteristics of SFOAEs, including detection rate, musical training influence, and gain function. Sixty-five normal hearing subjects (15 musicians and 50 non-musicians, aged 16–45 years) were tested and analyzed at the probe level of 30 and 50 dB sound pressure levels (SPL) in the center frequency of 1 and 4 kHz in the study. The results indicate that (1) the detection rates of SFOAE are sensitive to the gender, (2) musicians reveal enhanced hearing capacity and SFOAE amplitudes compared with non-musicians, and (3) probe frequency has a significant effect on the compression threshold of SFOAE. Our findings highlight the importance of SFOAE in the clinical hearing screening and diagnosis and emphasize the use of musical training for the rehabilitation enhancement of the auditory periphery and hearing threshold.

Industrial Noise Pollution and Its Impact on the Hearing Capacity of Workers: A Case Study of Gujranwala City, Pakistan

The main purpose of this study was to analyze and evaluate the impacts of industrial noise pollution onhearing of workers in Gujranwala. Noise pollution levels were measured at fifty locations with the help of sound levelmeter, which was placed at a height above 1.2 meters from the ground. Two hundred workers were interviewed throughquestionnaire method. Different statistical tests correlation and chi-square were applied to analyze the noise pollutionlevel in Gujranwala city. Impacts of industrial noise pollution on hearing of workers were shown in different mapsusing interpolation and buffers. The present study concluded that noise pollution levels were exceeding the WHOpermissible limit of noise pollution at all sample locations. Workers of factories were suffering from annoyance,hypertension, irritation, interference with speech communication and sleep disturbance. Thus, it is necessary to possessa hearing discussion program in factories. One of its main parts is education to raise the consciousness of workers aboutnoise risks and techniques of prevention. Lastly, the issues of noise annoyance should be included in all future studieson the usage of hearing protection devices.

Industrial Noise Pollution and Its Impact on the Hearing Capacity of Workers: A Case Study of Gujranwala City, Pakistan

The main purpose of this study was to analyze and evaluate the impacts of industrial noise pollution onhearing of workers in Gujranwala. Noise pollution levels were measured at fifty locations with the help of sound levelmeter, which was placed at a height above 1.2 meters from the ground. Two hundred workers were interviewed throughquestionnaire method. Different statistical tests correlation and chi-square were applied to analyze the noise pollutionlevel in Gujranwala city. Impacts of industrial noise pollution on hearing of workers were shown in different mapsusing interpolation and buffers. The present study concluded that noise pollution levels were exceeding the WHOpermissible limit of noise pollution at all sample locations. Workers of factories were suffering from annoyance,hypertension, irritation, interference with speech communication and sleep disturbance. Thus, it is necessary to possessa hearing discussion program in factories. One of its main parts is education to raise the consciousness of workers aboutnoise risks and techniques of prevention. Lastly, the issues of noise annoyance should be included in all future studieson the usage of hearing protection devices.

Twelve-year results of LINAC-based radiosurgery for vestibular schwannomas.

To report long-term outcomes of 53patients with vestibular schwannomas (VS) submitted to asingle high-dose LINAC-based radiosurgery (SRS) in our institution. 48 (92%) patients were evaluable for clinical and MRI response as well as late toxicity. At amedian follow-up of 12years (range 2-16years), local control (LC), hearing capacity, trigeminal and facial nerve function, and toxicity were assessed. Hearing capacity was classified according to the Gardner-Robertson scale, where classI-II patients had "serviceable hearing." Median dose of SRS was 16.5 Gy (range 13-20Gy) and median tumor volume 1.7 cm3 (range 0.09-7.4 cm3). 35 (73%) patients were treated with SRS alone, in the remaining 13 (27%) patients, SRS was performed as salvage therapy for recurrent or progressive tumors after previous microsurgery. Before SRS, 44patients (92%) had hearing loss and 25 (52%) had "non-serviceable" hearing. Tumor extension, classified with Koos categories, was gradeI-II in 27 (56%) and gradeIII-IV in 21 (44%) cases. LC was 100% and hearing preservation in "serviceable hearing" patients was 91%. 4 (11%) patients developed incomplete and intermittent ipsilateral facial nerve palsy which regressed in amedian time of 6months. Trigeminal toxicity was registered in 11 (23%) patients, reversible in 6 (13%) and permanent in 5 (10%). Only Koos tumor gradeIII-IV significantly influenced late toxicity (p = 0.01). LC and hearing preservation after SRS were excellent. Toxicity proved acceptable. Although the median administered dose (16.5 Gy) was rather high, the only factor which significantly influenced late toxicity was Koos tumor gradeIII-IV.

Inner Ear Genes Underwent Positive Selection and Adaptation in the Mammalian Lineage.

The mammalian inner ear possesses functional and morphological innovations that contribute to its unique hearing capacities. The genetic bases underlying the evolution of this mammalian landmark are poorly understood. We propose that the emergence of morphological and functional innovations in the mammalian inner ear could have been driven by adaptive molecular evolution. In this work, we performed a meta-analysis of available inner ear gene expression data sets in order to identify genes that show signatures of adaptive evolution in the mammalian lineage. We analyzed ∼1,300 inner ear expressed genes and found that 13% show signatures of positive selection in the mammalian lineage. Several of these genes are known to play an important function in the inner ear. In addition, we identified that a significant proportion of genes showing signatures of adaptive evolution in mammals have not been previously reported to participate in inner ear development and/or physiology. We focused our analysis in two of these genes: STRIP2 and ABLIM2 by generating null mutant mice and analyzed their auditory function. We found that mice lacking Strip2 displayed a decrease in neural response amplitudes. In addition, we observed a reduction in the number of afferent synapses, suggesting a potential cochlear neuropathy. Thus, this study shows the usefulness of pursuing a high-throughput evolutionary approach followed by functional studies to track down genes that are important for inner ear function. Moreover, this approach sheds light on the genetic bases underlying the evolution of the mammalian inner ear.

Occupational noise-induced hearing loss among dental professionals.

The purpose of this study was to determine whether the persistent high-frequency noise produced by dental equipment could cause hearing impairment among the dental professionals in the United Arab Emirates (UAE). This cross-sectional study was conducted to evaluate the hearing capacity of 90 randomly selected dental practitioners from different specialties working in the UAE. The participants were approached in their workplace and their hearing capacity was evaluated using the pure tone audiometer. Twenty dental practitioners suffered from hearing impairment, which constitutes 22.2% of the studied sample. At high frequencies, left ears were more affected than right ears, but this was not statistically significant. There was a direct relationship between working hours per week and the hearing capacity, but this did not reach a statistically significant level. The lowest hearing capacity was detected in males at a significantly lower value compared to females. Positive correlation was found between years of experience and reduced hearing capacity among dental practitioners. In addition, males had a significantly higher median count of severely affected hearing frequencies compared to females. Online pure tone audiometric testing is an easy, cost-effective tool that can be used to self-assess the hearing capacity of dental professionals, and it is recommended to perform this test annually.

Comparative study of anterior tucking and cartilage support tympanoplasty with respect to graft uptake and hearing outcome

&lt;p class="abstract"&gt;&lt;strong&gt;Background:&lt;/strong&gt; Tympanic membrane perforation in chronic otitis media exposes the middle ear mucosa to exogenous source of infection and also produces conductive hearing loss. To overcome this problem various surgical techniques of tympanoplasty using different graft materials have been tried with varying degrees of success rate. The purpose of this study was to compare anterior tucking and cartilage support tympanoplasty with respect to graft uptake and hearing outcome.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Methods:&lt;/strong&gt; This prospective study comprised of 50 consecutive patients with chronic otitis media of tubo tympanic type during October 2015 to September 2017, which were divided into two groups. Group A (25 patients) underwent type 1 tympanoplasty with anterior tucking method, Group B (25 patients) underwent type 1 tympanoplasty with cartilage support. The primary result was measured in view of graft uptake &amp;amp; hearing capacity outcome at 6 months post operatively by performing pure tone audiometry. &lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Results:&lt;/strong&gt; In anterior tucking tympanoplasty group out of 25 patients, the graft uptake was good in 22 patients and 23 patients showed good improvement in hearing, while in cartilage support tympanoplasty group all the 25 patients the graft uptake was good and all showed good hearing improvement postoperatively. In our study both the groups have significant hearing improvement and in cartilage support tympanoplasty results were better.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Conclusions:&lt;/strong&gt; The aim of tympanoplasty is to treat middle ear and tympanic membrane defects. In this study we subjected the patients for anterior tucking and cartilage support tympanoplasty for two different groups respectively and both methods showed significant hearing improvement.&lt;/p&gt;

Characterization of harmonic response of human middle ear using finite element approach

Human middle ear (ME) is an important organ of the auditory system. Sound energy stimulates the cochlear fluids present in the inner ear. Ossicular chain, a part of human middle ear consists of Tympanic membrane (TM), ossicles, ligaments and muscles. Hearing loss is reported when the ossicles in the chain gets degraded. Surgical intervention is one of the approaches to overcome the situation. The possibility of replacement of damaged ossicles with normal biocompatible biomaterials is explored in the current study. To study the sound transfer function, a FE model is developed using μCT (Computed Tomography) scan data imported in MIMICS Research 19.0 (Materialise Interactive Medical Image Control System) modeling software. The harmonic response at the stapes footplate and umbo is examined with the assumption that sound pressure is incident from lateral side of eardrum. Pathological conditions are analysed to determine the gain or loss in hearing capacity for Cholesteatoma, Partial mallear fixation and variations of material properties in Tympanic membrane (TM). The human audible sound pressure levels (SPLs) of 60, 80, 100 and 120 dB are applied on eardrum within frequency range of 100 Hz–10,000 Hz. The results are compared with healthy ear to investigate gain or loss in hearing capacity for these pathologies.

Modulation of Cognitive and Emotional Control in Age-Related Mild-to-Moderate Hearing Loss.

Progressive hearing loss is a common phenomenon in healthy aging and may affect the perception of emotions expressed in speech. Elderly with mild to moderate hearing loss often rate emotional expressions as less emotional and display reduced activity in emotion-sensitive brain areas (e.g., amygdala). However, it is not clear how hearing loss affects cognitive and emotional control mechanisms engaged in multimodal speech processing. In previous work we showed that negative, task-relevant and -irrelevant emotion modulates the two types of control in younger and older adults without hearing loss. To further explore how reduced hearing capacity affects emotional and cognitive control, we tested whether moderate hearing loss (>30 dB) at frequencies relevant for speech impacts cognitive and emotional control. We tested two groups of older adults with hearing loss (HL; N = 21; mean age = 70.5) and without hearing loss (NH; N = 21; mean age = 68.4). In two EEG experiments participants observed multimodal video clips and either categorized pronounced vowels (cognitive conflict) or their emotions (emotional conflict). Importantly, the facial expressions were either matched or mismatched with the corresponding vocalizations. In both conflict tasks, we found that negative stimuli modulated behavioral conflict processing in the NH but not the HL group, while the HL group performed at chance level in the emotional conflict task. Further, we found that the amplitude difference between congruent and incongruent stimuli was larger in negative relative to neutral N100 responses across tasks and groups. Lastly, in the emotional conflict task, neutral stimuli elicited a smaller N200 response than emotional stimuli primarily in the HL group. Consequently, age-related hearing loss not only affects the processing of emotional acoustic cues but also alters the behavioral benefits of emotional stimuli on cognitive and emotional control, despite preserved early neural responses. The resulting difficulties in the multimodal integration of incongruent emotional stimuli may lead to problems in processing complex social information (irony, sarcasm) and impact emotion processing in the limbic network. This could be related to social isolation and depression observed in the elderly with age-related hearing loss.

Combined effect of non-bacteriolytic antibiotic and inhibition of matrix metalloproteinases prevents brain injury and preserves learning, memory and hearing function in experimental paediatric pneumococcal meningitis

BackgroundPneumococcal meningitis is associated with high mortality and morbidity rates. Up to 50% of survivors show neurologic sequelae including hearing loss, cognitive impairments and learning disabilities, being particularly detrimental in affected infants and children where adjuvant therapy with dexamethasone has no proven beneficial effect. We evaluated the effect of concomitantly targeting specific pathophysiological mechanisms responsible for brain damage—i.e. matrix-metalloproteinase (MMP) activity and the exacerbated cerebral inflammation provoked through antibiotic-induced bacterial lysis. Here, we combined adjunctive therapies previously shown to be neuroprotective when used as single adjuvant therapies.MethodsEleven-day-old Wistar rats were infected intracisternally with 6.44 ± 2.17 × 103 CFU Streptococcus pneumoniae and randomised for treatment with ceftriaxone combined with (a) single adjuvant therapy with daptomycin (n = 24), (b) single adjuvant therapy with Trocade (n = 24), (c) combined adjuvant therapy (n = 66) consisting of daptomycin and Trocade, or (d) ceftriaxone monotherapy (n = 42). Clinical parameters and inflammatory CSF cytokine levels were determined during acute meningitis. Cortical damage and hippocampal apoptosis were assessed 42 h after infection. Morris water maze and auditory brainstem responses were used to assess neurofunctional outcome 3 weeks after infection.ResultsWe found significantly reduced apoptosis in the hippocampal subgranular zone in infant rats receiving adjuvant Trocade (p < 0.01) or combined adjuvant therapy (p < 0.001). Cortical necrosis was significantly reduced in rats treated with adjuvant daptomycin (p < 0.05) or combined adjuvant therapy (p < 0.05) compared to ceftriaxone monotherapy. Six hours after treatment initiation, CSF cytokine levels were significantly reduced for TNF-α (p < 0.01), IL-1β (p < 0.01), IL-6 (p < 0.001) and IL-10 (p < 0.01) in animals receiving combined adjuvant intervention compared to ceftriaxone monotherapy. Importantly, combined adjuvant therapy significantly improved learning and memory performance in infected animals and reduced hearing loss (77.14 dB vs 60.92 dB, p < 0.05) by preserving low frequency hearing capacity, compared to ceftriaxone monotherapy.ConclusionCombined adjuvant therapy with the non-bacteriolytic antibiotic daptomycin and the MMP inhibitor Trocade integrates the neuroprotective effects of both single adjuvants in experimental paediatric pneumococcal meningitis by reducing neuroinflammation and brain damage, thereby improving neurofunctional outcome. This strategy represents a promising therapeutic option to improve the outcome of paediatric patients suffering from pneumococcal meningitis.

Characterisation of upper airway obstructions using wide-band snoring sounds

Background: Obstructive sleep apnea (OSA) is associated with partial (hypopnea) and full (apnea) upper airway obstructions. The standard method for identifying these obstructions and leading to OSA diagnosis is overnight polysomnography (PSG). One of the important outcomes of PSG is the apnea-hypopnea index (AHI), which represents the average number of obstructions per hour, computed over the total duration of sleep. AHI is a single number summary of the dynamics of the upper airway during sleep. PSG is complicated, requires more than 20 body-contact sensors and is not available for population screening. There is a need for simple and automated technologies that can characterise the upper airways in more detail. In this paper, we address this need by proposing a method to identify individual apnea and hypopnea events via the analysis of breathing and snoring sounds collected through a microphone, which requires no physical contact with a subject. We also explore snoring and breathing sounds over a wide frequency band, exceeding the capacity of human hearing. Hypothesis: Our primary hypothesis is that snoring sounds carry sufficient information to characterise partial and full collapses of the upper airway in OSA. We also hypothesise that snoring sounds have a frequency spectrum extending beyond the human hearing range, and the spectrum's high-frequency components can provide critical information on airway collapses. Method: We recorded streams of respiratory sounds using a bedside microphone (4 Hz–100 kHz) from patients undergoing PSG studies in a sleep laboratory. Audio streams were divided into non-overlapping segments of 5 s durations. Segments containing partial or full snores were manually extracted for further investigation. Altogether we extracted 19,715 such segments from 18 subjects. We then obtained the power spectrum of each of the segments and estimated spectral energies in 16 frequency bands covering the range: 4 Hz–35 kHz. Significantly, when the upper airway narrows during or in the vicinity of apnea/hypopnea events, spectral energy tends to shift to higher frequencies. In this research, we developed indices which capture these energy shifts and function as surrogate measures of airway patency. We then calibrated proposed sound based indices using PSG derived apnea and hypopnea events. Our indices allowed us to individually pick apnea and hypopnea events and estimate a sound based AHI which we named the frequency spectrum index. Results: Our results indicated that snoring sounds extend to frequencies beyond the upper limit of the nominal hearing range, i.e. 20 kHz (p < 0.0001). At the patient level, the frequency spectrum index shows a correlation of r = 0.80 with the PSG based hypopnea index, with the highest correlation in the frequency band of 5–15 kHz. Similarly, the frequency spectrum index showed a correlation of r = 0.82 with the PSG based obstructive apnea index, where, interestingly, the highest correlation occurs in the 25–30 kHz band, which is outside the human range of hearing band. Conclusion: The snoring sound based frequency spectrum index has the potential to characterise full and partial closures of the upper airway. Snoring sounds are spread over a wide spectrum and critical information on the full closure of the upper airway is predominantly carried in frequencies beyond human hearing capacity.

The Transplantation of hBM-MSCs Increases Bone Neo-Formation and Preserves Hearing Function in the Treatment of Temporal Bone Defects - on the Experience of Two Month Follow Up.

Temporal bone reconstruction is a persisting problem following middle ear cholesteatoma surgery. Seeking to advance the clinical transfer of stem cell therapy we attempted the reconstruction of temporal bone using a composite bioartificial graft based on a hydroxyapatite bone scaffold combined with human bone marrow-derived mesenchymal stromal cells (hBM-MSCs). The aim of this study was to evaluate the effect of the combined biomaterial on the healing of postoperative temporal bone defects and the preservation of physiological hearing functions in a guinea pig model. The treatment's effect could be observed at 1 and 2months after implantation of the biomaterial, as opposed to the control group. The clinical evaluation of our results included animal survival, clinical signs of an inflammatory response, and exploration of the tympanic bulla. Osteogenesis, angiogenesis, and inflammation were evaluated by histopathological analyses, whereas hBM-MSCs survival was evaluated by immunofluorescence assays. Hearing capacity was evaluated by objective audiometric methods, i.e. auditory brainstem responses and otoacoustic emission. Our study shows that hBM-MSCs, in combination with hydroxyapatite scaffolds, improves the repair of bone defects providing a safe and effective alternative in their treatment following middle ear surgery due to cholesteatoma.

Hearing capacities and morphology of the auditory system in Serrasalmidae (Teleostei: Otophysi)

Like all otophysan fishes, serrasalmids (piranhas and relatives) possess a Weberian apparatus that improves their hearing capacities. We compared the hearing abilities among eight species of serrasalmids having different life-history traits: herbivorous vs. carnivorous and vocal vs. mute species. We also made 3D reconstructions of the auditory system to detect potential morphological variations associated with hearing ability. The hearing structures were similar in overall shape and position. All the species hear in the same frequency range and only slight differences were found in hearing thresholds. The eight species have their range of best hearing in the lower frequencies (50–900 Hz). In vocal serrasalmids, the range of best hearing covers the frequency spectrum of their sounds. However, the broad overlap in hearing thresholds among species having different life-history traits (herbivorous vs. carnivorous and vocal vs. non-vocal species) suggests that hearing ability is likely not related to the capacity to emit acoustic signals or to the diet, i.e. the ability to detect sounds is not associated with a given kind of food. The inner ear appears to be highly conservative in this group suggesting that it is shaped by phylogenetic history or by other kinds of constraints such as predator avoidance.

Avoidance of seismic survey activities by penguins

Seismic surveys in search for oil or gas under the seabed, produce the most intense man-made ocean noise with known impacts on invertebrates, fish and marine mammals. No evidence to date exists, however, about potential impacts on seabirds. Penguins may be expected to be particularly affected by loud underwater sounds, due to their largely aquatic existence. This study investigated the behavioural response of breeding endangered African Penguins Spheniscus demersus to seismic surveys within 100 km of their colony in South Africa, using a multi-year GPS tracking dataset. Penguins showed a strong avoidance of their preferred foraging areas during seismic activities, foraging significantly further from the survey vessel when in operation, while increasing their overall foraging effort. The birds reverted to normal behaviour when the operation ceased, although longer-term repercussions on hearing capacities cannot be precluded. The rapid industrialization of the oceans has increased levels of underwater anthropogenic noises globally, a growing concern for a wide range of taxa, now also including seabirds. African penguin numbers have decreased by 70% in the last 10 years, a strong motivation for precautionary management decisions, including the exclusion of seismic exploratory activities within at least 100 km of their breeding colonies.

Regular Exposure to Cowbells Affects the Behavioral Reactivity to a Noise Stimulus in Dairy Cows.

In alpine regions, cows are often equipped with bells during pasture season to ensure that farmers can locate them. Constant exposure to the chime of a bell may affect cows’ acoustic perception in general. The aim of this study is to test whether routine bell exposure affects the reactivity to a noise stimulus and might be associated with hearing impairment in cows. For the assessment, behavioral and cardiac indicators were used as indirect measures of hearing capacity. Cows that were either used to wearing a bell or not were exposed to a playback of low and high amplitude (=varying loudness). In addition, we tested whether wearing earplugs, mimicking hearing impairment, reduced the cows’ reactivity toward the playback. On 24 farms, half of them routinely using cowbells, 96 Brown Swiss cows were tested in a 2 × 2 factorial cross-over design (65 or 85 dB, without or with earplugs) in a balanced order. The effects of bell experience, amplitude, and earplugs on the latency to the first behavioral and cardiac response to a 5-s playback were analyzed using linear mixed-effects models, considering dependencies within the data set. Cows reacted faster without earplugs and when they were exposed to 85 dB compared with 65 dB. The proportion of cows leaving the feeding rack after onset of the playback was reduced by bell experience and earplugs and was increased when exposed to 85 dB compared with 65 dB. Exposure without earplugs to 85 dB but not to 65 dB increased heart rate. Heart rate and heart rate variability indicated increased sympathetic activation during the exposure to 85 dB compared with 65 dB. In general, behavioral and cardiac indicators did not indicate severe hearing impairment due to routine bell exposure. The 85-dB stimulus increased arousal and avoidance compared with the 65-dB stimulus, with bell experience and earplugs leading to a general decrease in avoidance of the stimulus. This may reflect an altered acoustic perception of the playback stimulus in dairy cows that are routinely exposed to bells.

Evaluation of transient-evoked otoacoustic emissions in a healthy 1 to 10 year pediatric cohort in Sub-Saharan Africa

ObjectiveTransient-evoked otoacoustic emissions (TEOAEs) monitor cochlear function. High pass rates have been reported for industrialized countries. Pass rates in low and middle income countries such as Sub-Saharan Africa are rare, essentially lower and available for children up to 4 years of age and frequently based on hospital recruitments.This study aims at providing additional TEOAE pass rates of a healthy Sub-Saharan cohort aged 1–10 years with data from Gabon, Ghana and Kenya. Potentially confounding factors (recruitment site, age) are taken into consideration. MethodsHealthy children were recruited in hospitals, schools and kindergartens. Inclusion criteria were age 1–10 years and normal otoscopic findings. Exclusion criteria were any sickness or physical ailment potentially impairing the hearing capacity. Five measurements per ear were performed with Capella Cochlear Emission Analyzer (MADSEN, Germany). An overall wave reproducibility of above 60% served as pass-criterion. Pass rates were compared between recruitment sites and age groups (1–5 and 6–10 years). ResultsOverall pass rate was 87.5% (n = 264; 231 passes vs. 33 fails). Of these 84.0% of hospital recruited children passed (n = 156; 131 passes vs. 25 fails), compared to 92.6% of community recruitments (n = 108; 100 passes vs. 8 fails), which was significantly different p = 0.039). If analyzed by age groups, this difference was only observed in children younger than 6 years (p = 0.007). ConclusionHospitals as recruitment sites for healthy controls seem to affect TEOAE pass rates. We advise for a cautious approach when recruiting healthy TEOAE control collectives under the age of 6 in a hospital setting. In children older than 6 years conventional pure-tone audiometry remains the standard method for hearing screening.

Spectrin βV adaptive mutations and changes in subcellular location correlate with emergence of hair cell electromotility in mammalians

The remarkable hearing capacities of mammals arise from various evolutionary innovations. These include the cochlear outer hair cells and their singular feature, somatic electromotility, i.e., the ability of their cylindrical cell body to shorten and elongate upon cell depolarization and hyperpolarization, respectively. To shed light on the processes underlying the emergence of electromotility, we focused on the βV giant spectrin, a major component of the outer hair cells' cortical cytoskeleton. We identified strong signatures of adaptive evolution at multiple sites along the spectrin-βV amino acid sequence in the lineage leading to mammals, together with substantial differences in the subcellular location of this protein between the frog and the mouse inner ear hair cells. In frog hair cells, spectrin βV was invariably detected near the apical junctional complex and above the cuticular plate, a dense F-actin meshwork located underneath the apical plasma membrane. In the mouse, the protein had a broad punctate cytoplasmic distribution in the vestibular hair cells, whereas it was detected in the entire lateral wall of cochlear outer hair cells and had an intermediary distribution (both cytoplasmic and cortical, but restricted to the cell apical region) in cochlear inner hair cells. Our results support a scenario where the singular organization of the outer hair cells' cortical cytoskeleton may have emerged from molecular networks initially involved in membrane trafficking, which were present near the apical junctional complex in the hair cells of mammalian ancestors and would have subsequently expanded to the entire lateral wall in outer hair cells.

The Category Subdivision Scale of Subjective Hearing Impairment a Screening Instrument for Reduced Hearing Capacity

Demographic development will lead to an aging working population. Therefore, dealing with age-related impairments like hearing impairment has become a central issue. Thus, there is need in a valid screening instrument for hearing impairment. So, a new simple method, the Category Subdivision Scale of Subjective Hearing Impairment (CSS-SHI), was tested. Data are collected within five different studies (236 employees): One pilot study and four studies to validate and replicate the results of the pilot study. In each study the participants first assessed their self-reported hearing impairment using the CSS-SHI and afterwards hearing capacity was measured by audiometry. The results show that self-reported hearing impairment measured with CSS-SHI correlates substantially with pure-tone audiometry. The CSS-SHI is a very fast and easy to use screening instrument that allows a valid statement about hearing impairment, also when the situation, sample size and/or environment do not allow the use of a pure-tone audiometry.