Pure-tone audiogram: measuring auditory sensitivity over the age

In this study a pure tone audiogram was developed under the Matlab® mathematical software. Audiogram measurements were performed to 35 subjects belonging to the female and male and aged between 10 and 88 years old. Some of the subjects with more advanced age had hearing problems over the course of age, however, none of them was carrying any type of hearing aid. The threshold of the Sound Pressure Level (SPL) was recorded under 12 pure tones between 125 Hz and 15 kHz. The developed pure-tone audiogram confirmed its ability to produce auditory brainstem responses (ABRs). Statistical analysis of the SPL threshold shows no differences between genders and confirms the correlation between age and loss of sensitivity, more accentuated for higher frequency tones. A strong loss of sensitivity was observed after the decade of 60 years old

Individual differences in auditory brainstem response wave characteristics : relations to different aspects of peripheral hearing loss

Little is known about how outer hair cell loss interacts with noise-induced and age-related auditory nerve degradation (i.e., cochlear synaptopathy) to affect auditory brainstem response (ABR) wave characteristics. Given that listeners with impaired audiograms likely suffer from mixtures of these hearing deficits and that ABR amplitudes have successfully been used to isolate synaptopathy in listeners with normal audiograms, an improved understanding of how different hearing pathologies affect the ABR source generators will improve their sensitivity in hearing diagnostics. We employed a functional model for human ABRs in which different combinations of hearing deficits were simulated and show that highfrequency cochlear gain loss steepens the slope of the ABRWave-V latency versus intensity and amplitude versus intensity curves. We propose that grouping listeners according to a ratio of these slope metrics (i.e., the ABR growth ratio) might offer a way to factor out the outer hair cell loss deficit and maximally relate individual differences for constant ratios to other peripheral hearing deficits such as cochlear synaptopathy. We compared the model predictions to recorded click-ABRs from 30 participants with normal or high-frequency sloping audiograms and confirm the predicted relationship between the ABR latency growth curve and audiogram slope. Experimental ABR amplitude growth showed large individual differences and was compared with the Wave-I amplitude, Wave-V/I ratio, or the interwaveI-W latency in the same listeners. The model simulations along with the ABR recordings suggest that a hearing loss profile depicting the ABR growth ratio versus the Wave-I amplitude or Wave-V/I ratio might be able to differentiate outer hair cell deficits from cochlear synaptopathy in listeners with mixed pathologies

Current Trends in Audiological Practices and Implications for Developing Countries

This paper examines the current trends in audiological practices in Nigeria, as it makes case for compulsory use of electro- physiological tests in determining the hearing potentials of children in the country, as against the use of behavioural audiometric strategy which requires the active participation of the patients. Varieties of electro- physiological tests such as Auditory Brainstem Response Test (ABR), Oto- Acoustic Emission, and modern advances such as cochlear implants and auditory brainstem implants for Neuro- Fibromatosis type 2 (NF2) as practiced in developed countries were explained. These current trends in audiological practices should serve as a catalyst to stimulate the developing countries in managing hearing and speech disorders. Keywords: Audiological practices, Developing countries, Audiological investigations, Audiological  Managemen

Utilization of the chirp stimulus in auditory brainstem response measurements

Välittömästi äänistimulusta seuraavaa, aivorungosta lähtöisin olevaa sähköistä aktiviteettia kutsutaan auditoriseksi aivorunkovasteeksi (ABR, auditory brainstem response). ABR:ää käytetään laajalti kuulon objektiiviseen testaamiseen. Siinä missä perinteisessä äänesaudiometriassa koehenkilön tulee vastata testiääniin ennalta määrätyllä tavalla, ABR voidaan mitata ilman koehenkilön aktiivista osallistumista. Hiljattain ABR-mittauksia varten on kehitetty uudenlainen stimulus: chirp. Chirpin tarkoituksena on tuottaa suurempi ABR-amplitudi lisäämällä sisäkorvan karvasolujen aktiviteetin yhtäaikaisuutta. 1,5 - 2-kertaisia parannuksia onkin raportoitu verrattuna perinteisiin stimuluksiin. Tässä työssä perinteisiä click- ja tone burst -stimuluksia on vertailtu vastaaviin laajakaistaiseen chirpiin ja taajuusspesifeihin kapeakaistaisiin chirpeihin. ABR-kynnystasoja vertailtiin myös toisella objektiivisella metodilla, ASSR:llä saatuihin kynnystasoihin. Vasteet mitattiin kuudelta normaalikuuloiselta ja viideltä huonokuuloiselta koehenkilöltä Interacousticsin Eclipse-järjestelmällä. Perinteisten ja chirp-stimulusten eroja tutkittiin vertailemalla normaalikuuloisilta mitattujen vasteiden amplitudeja. Myös kaikilta koehenkilöiltä mitattuja kynnysarvoja verrattiin äänesaudiometrialla määriteltyihin kuulokynnyksiin. Tulosten perusteella perinteisten stimulusten ja vastaavien chirp stimulusten välillä ei löytynyt tilastollisesti merkitseviä eroja. ASSR- ja ABR-kynnysarvojen luotettava vertailu ei myöskään ollut mahdollista johtuen saatujen kynnysarvojen pienestä määrästä. Johtopäätöksissä todettiin, että tuloksiin on todennäköisesti vaikuttanut tutkimuksessa käytettyjen kuulokkeiden tyyppi. Aiemmissa, chirpin paremmuuden kannalla olleissa tutkimuksissa, mittaukset tehtiin käyttäen toista kuulokemallia. Myös kuulonaleneman vaikutukset chirp stimuluksella suoritettuihin ABR-mittauksiin ovat huonosti tunnettuja, antaen aihetta jatkotutkimuksille.The electrical activity originating from the auditory structures of the brainstem is called the auditory brainstem response (ABR). The ABR is used widely for objective assessment of the hearing system. Whereas traditional pure tone audiometry requires the test subject to respond to probe tones in a predefined manner, the ABR can be recorded without any active participation of the subject. Recently, a new kind of stimulus has been developed for ABR measurements. This stimulus, called chirp, aims at increasing the ABR amplitude by promoting synchronous firing of the hair cells in the inner ear. 1,5 - 2 times higher ABR amplitudes have indeed been recorded using the chirp when compared to traditional stimuli. In this thesis, traditional click and tone burst stimuli were compared to corresponding chirp variants; the broadband chirp and frequency-specific narrowband chirps. Also, the ABR results were compared to those obtained by another objective method, the auditory steady-state response (ASSR). Responses were obtained from six normal-hearing subjects and five hard-of-hearing subjects using the Eclipse platform from Interacoustics. In normal-hearing subjects, the ABR amplitudes were compared between traditional and chirp stimuli. In all subjects, ABR and ASSR thresholds were compared to the behavioral thresholds. Results failed to show significant differences between traditional stimuli and corresponding chirp variants. Also, comparison of and ASSR thresholds could not be done reliably because of the small number of obtained thresholds. It was concluded that the results were influenced by the type of the insert earphones used in this study. Previous results in favour of the chirp have been obtained using a different type of earphones. Also, it was suggested that the influence of hearing loss on chirp-elicited ABRs be investigated in the future

Hearing Loss and the Elderly - A Primer

Hearing impairment, is very common among the elderly. In many of them it can be so disabling that it affects normal day to day activities, impairs communication and puts them at risk of social isolation and psychological problems. Fortunately, while it cannot be reversed most times, hearing loss in the elderly can be so well managed that the elderly can enjoy a good quality of life. This article is a review on presbycusis (age-related hearing loss), the physiology and management as a means of sensitizing medical personnel and those working with the elderly

Hearing Ability with Age in Northern European Women: A New Web-Based Approach to Genetic Studies

Age-related hearing impairment (ARHI) affects 25–40% of individuals over the age of 65. Despite the high prevalence of this complex trait, ARHI is still poorly understood. We hypothesized that variance in hearing ability with age is largely determined by genetic factors. We collected audiologic data on females of Northern European ancestry and compared different audiogram representations. A web-based speech-to-noise ratio (SNR) hearing test was compared with pure-tone thresholds to see if we could determine accurately hearing ability on people at home and the genetic contribution to each trait compared. Volunteers were recruited from the TwinsUK cohort. Hearing ability was determined using pure-tone audiometry and a web-based hearing test. Different audiogram presentations were compared for age-correlation and reflection of audiogram shape. Using structural equation modelling based on the classical twin model the heritability of ARHI, as measured by the different phenotypes, was estimated and shared variance between the web-based SNR test and pure-tone audiometry determined using bivariate modelling. Pure-tone audiometric data was collected on 1033 older females (age: 41–86). 1970 volunteers (males and females, age: 18–85) participated in the SNR. In the comparison between different ARHI phenotypes the difference between the first two principle components (PC1–PC2) best represented ARHI. The SNR test showed a sensitivity and specificity of 89% and 80%, respectively, in comparison with pure-tone audiogram data. Univariate heritability estimates ranged from 0.70 (95% CI: 0.63–0.76) for (PC1–PC2) to 0.56 (95% CI: 0.48–0.63) for PC2. The genetic correlation of PC1–PC2 and SNR was −0.67 showing that the 2 traits share variances attributed to additive genetic factors. Hearing ability showed considerable heritability in our sample. We have shown that the SNR test provides a useful surrogate marker of hearing. This will enable a much larger sample to be collected at a fraction of the cost, facilitating future genetic association studies

Effects of moderate-level sound exposure on behavioral thresholds in chinchillas

Normal audiometric thresholds following noise exposure have generally been considered as an indication of a recovered cochlea and intact peripheral auditory system, yet recent animal work has challenged this classic assumption. Moderately noise-exposed animals have been shown to have permanent loss of synapses on inner hair cells (IHCs) and permanent damage to auditory nerve fibers (ANFs), specifically the low-spontaneous rate fibers (low-SR), despite normal electrophysiological thresholds. Loss of cochlear synapses, known as cochlear synaptopathy, disrupts auditory-nerve signaling, which may result in perceptual speech deficits in noise despite normal audiometric thresholds. Perceptual deficit studies in humans have shown evidence consistent with the idea of cochlear synaptopathy. To date, there has been no direct evidence linking cochlear synaptopathy and perceptual deficits. Our research aims to develop a cochlear synaptopathy model in chinchilla, similar to previously established mouse and guinea pig models, to provide a model in which the effects of cochlear synaptopathy on behavioral and physiological measures of low-frequency temporal coding can be explored. ^ Positive-reinforcement operant-conditioning was used to train animals to perform auditory detection behavioral tasks for four frequencies: 0.5, 1, 2, and 4 kHz. Our goal was to evaluate the detection abilities of chinchillas for tone-in-noise and sinusoidal amplitude modulated (SAM) tone behavioral tasks, which are tasks thought to rely on low-SR ANFs for encoding. Testing was performed before and after exposure to an octave-band noise exposure centered at 1 kHz for 2 hours at 98.5 dB SPL. This noise exposure produced the synaptopathy phenotype in naïve chinchillas, based on auditory-brainstem responses (ABRs), otoacoustic emissions (OAEs) and histological analyses. Threshold shift and inferred synaptopathy was determined from ABR and OAE measures in our behavioral animals. ^ Overall, we have shown that chinchillas, similar to mice and guinea pigs, can display cochlear synaptopathy phenotype following moderate-level sound exposure. This finding was seen in naïve exposed chinchillas, but our results suggest the susceptibility to noise can vary between naïve and behavioral cohorts because minimal physiological evidence for synaptopathy was observed in the behavioral group. Hearing sensitivity determined by a tone-in-quiet behavioral task on normal hearing chinchillas followed trends reported previously, and supported the lack of permanent threshold shift following moderate noise exposure. As we expected, thresholds determined in a tone-in-noise behavioral task were higher than thresholds measured in quiet. Behavioral thresholds measured in noise after moderate noise exposure did not show threshold shifts relative to pre-exposure thresholds in noise. As expected, chinchillas were more sensitive at detecting fully modulated SAM-tone signals than less modulated, with individual modulation depth thresholds falling within previously reported mammalian ranges. ^ Although we have only been able to confirm cochlear synaptopathy in pilot assays with naïve animals so far (i.e., not in the pilot behavioral animals), this project has developed an awake protocol for moderate-level noise exposure, an extension to our lab’s previous experience with high-level permanent damage noise exposure under anesthesia. Also, we successfully established chinchilla behavioral training and testing protocols on several auditory tasks, a new methodology to our laboratory, which we hope will ultimately allow us to identify changes in auditory perception resulting from moderate-level noise exposure

Prevalence of High-Frequency Notched Audiometric Configurations Among University Music Students and Faculty

The present study determines the prevalence of audiometric notched configurations suggestive of noise-induced hearing loss (NIHL) among students and faculty at the University of Northern Colorado (UNC) School of Music. The prevalence of NIHL was determined by analyzing the results of 233 hearing evaluations that were administered during Fall semester music student orientation. High-frequency notches were characterized by evaluating the hearing thresholds at 3, 4, or 6 kHz being 10 dB or worse than the thresholds at 2 and 8 kHz, as defined by Wilson and McArdle, (2013). The prevalence of high-frequency audiometric notches was examined in terms of notch depth, notch frequency, and ear symmetry and how such prevalence varied as a function of sex and instrument type. Results indicated that an overall occurrence of notched high-frequency hearing loss was 56.7% (n = 132). Unilateral notches (65.9%) were more common than bilateral notches (34.1%), and notches occurred most frequently at 6 kHz amongst males. Vocalists (22.7%, n = 30) and woodwind instrument musicians (20.5%, n = 27) had the highest prevalence of notches. This study supports the need to implement a comprehensive hearing loss prevention program at the UNC School of Music and supports the continued provision of hi-fidelity hearing protection to incoming freshman students

The search for noise-induced cochlear synaptopathy in humans:Mission impossible?

Animal studies demonstrate that noise exposure can permanently damage the synapses between inner hair cells and auditory nerve fibers, even when outer hair cells are intact and there is no clinically relevant permanent threshold shift. Synaptopathy disrupts the afferent connection between the cochlea and the central auditory system and is predicted to impair speech understanding in noisy environments and potentially result in tinnitus and/or hyperacusis. While cochlear synaptopathy has been demonstrated in numerous experimental animal models, synaptopathy can only be confirmed through post-mortem temporal bone analysis, making it difficult to study in living humans. A variety of non-invasive measures have been used to determine whether noise-induced synaptopathy occurs in humans, but the results are conflicting. The overall objective of this article is to synthesize the existing data on the functional impact of noise-induced synaptopathy in the human auditory system. The first section of the article summarizes the studies that provide evidence for and against noise-induced synaptopathy in humans. The second section offers potential explanations for the differing results between studies. The final section outlines suggested methodologies for diagnosing synaptopathy in humans with the aim of improving consistency across studies