Measures Of Hearing Sensitivity Research Articles

How the structures of the Risso’s Dolphin (Grampus griseus) affect sound propagation and reception

Like other odontocetes, Risso’s dolphins actively emit clicks and passively listen to the echoes during echolocation. However, Risso’s dolphin head anatomy differs from other odontocetes by a unique vertical cleft along the anterior surface of the forehead and a differently shaped lower jaw. In this study, 3D finite-element sound propagation and reception models were constructed based on CT data of a deceased Risso’s dolphin. Model results of sound propagation and reception were verified by finding good agreement with practical recording data from previous biosonar beam measurements and hearing sensitivity measurements. The cleft was filled with neighboring soft tissues, creating a hypothetical “cleftness” head. Comparison between sound travelling through a “cleftness” head versus an original head indicate that the distinctive cleft plays a limited role in biosonar sound propagation. Additionally, we digitally simulated the acoustic pathway for sounds to travel from the water into dolphin’s tympanoperiotic complexes (TPCs). The gular reception mechanism, previously discovered in Delphinus delphis and Ziphius cavirostris was also found in this species. Sound pressure levels and displacement (motion) of the TPCs were compared between the cases with/without the mandibular fats or mandible. The results demonstrate a wave-guiding role of the mandibular fats and a bone conductor role of the mandible to transfer acoustic energy to the TPCs.

Latencies of click-evoked auditory responses in a harbor porpoise exceed the time interval between subsequent echolocation clicks.

Most auditory evoked potential (AEP) studies in echolocating toothed whales measure neural responses to outgoing clicks and returning echoes using short-latency auditory brainstem responses (ABRs) arising a few ms after acoustic stimuli. However, little is known about longer-latency cortical AEPs despite their relevance for understanding echo processing and auditory stream segregation. Here, we used a non-invasive AEP setup with low click repetition rates on a trained harbor porpoise to test the long-standing hypothesis that echo information from distant targets is completely processed before the next click is emitted. We reject this hypothesis by finding reliable click-related AEP peaks with latencies of 90 and 160 ms, which are longer than 99% of click intervals used by echolocating porpoises, demonstrating that some higher-order echo processing continues well after the next click emission even during slow clicking. We propose that some of the echo information, such as range to evasive prey, is used to guide vocal-motor responses within 50-100 ms, but that information used for discrimination and auditory scene analysis is processed more slowly, integrating information over many click-echo pairs. We conclude by showing theoretically that the identified long-latency AEPs may enable hearing sensitivity measurements at frequencies ten times lower than current ABR methods.

Scaling of ear morphology across 127 bird species and its implications for hearing performance

The dimensions of auditory structures among animals of varying body size can have implications for hearing performance. Larger animals often have a hearing range focused on lower frequencies than smaller animals, which may be explained by several anatomical mechanisms in the ear and their scaling relationships. While the effect of size on ear morphology and hearing performance has been explored in some mammals, anurans and lizards, much less is known about the scaling relationships for the single-ossicle, internally-coupled ears of birds. Using micro- and nano-CT scans of the tympanic middle and inner ears of 127 ecologically and phylogenetically diverse bird species, spanning more than 400-fold in head mass (2.3 to 950 g), we undertook phylogenetically-informed scaling analyses to test whether 12 morphological traits, of functional importance to hearing, maintain their relative proportions with increasing head mass. We then extended our analysis by regressing these morphological traits with measures of hearing sensitivity and range to better understand morphological underpinnings of hearing performance. We find that most auditory structures scale together in equal proportions, whereas columella length increases disproportionately. We also find that the size of several auditory structures is associated with increased hearing sensitivity and frequency hearing limits, while head mass did not explain these measures. Although both birds and mammals demonstrate proportional scaling between auditory structures, the consequences for hearing in each group may diverge due to unique morphological predictors of auditory performance.

No Reduction in the 226-Hz Probe Tone Acoustic Reflex Amplitude Following Severe Inner Hair Cell Loss in Chinchillas.

The relationship between the middle ear acoustic reflex (AR) and inner hair cell (IHC) loss is currently unknown. Given that IHC are believed to convey nearly all acoustic information to the central auditory nervous system, it has been assumed that loss of IHC would significantly impact the AR. To evaluate this relationship, we assessed the presence and amplitude of the AR in chinchillas before and after treatment with carboplatin, an anticancer drug that reliably and selectively destroys IHC in this species. Baseline measures of hearing sensitivity, including auditory brainstem response (ABR) thresholds and distortion product otoacoustic emissions (DPOAE), were assessed and then re-evaluated following carboplatin treatment. Post-carboplatin ABR thresholds and DPOAE were found to be unchanged or slightly elevated; results were consistent with published reports. Our main hypothesis was that loss of IHC would abolish the reflex or significantly reduce its amplitude. Contrary to our hypothesis, the ipsilateral 226-Hz AR continued to be reliably elicited following carboplatin treatment. Post-mortem histological analysis confirmed significant IHC loss (65-85 %), but no measurable loss of outer hair cells (OHCs). Given that loss of IHC alone does not significantly reduce the 226-Hz AR, our results suggest that few IHC are needed to maintain the 226-Hz AR response. These results suggest additional studies are needed to better understand the role of IHC in the reflex arc, present opportunities to further study the reflex pathway, and could change how we use the clinical AR as a potential diagnostic tool for IHC dysfunction, including those related to IHC synaptopathy.

Comparison of Auditory Steady-State Responses With Conventional Audiometry in Older Adults.

Behavioral measures, such as pure-tone audiometry (PTA), are commonly used to determine hearing thresholds, however, PTA does not always provide reliable hearing information in difficult to test individuals. Therefore, objective measures of hearing sensitivity that require little-to-no active participation from an individual are needed to facilitate the detection and treatment of hearing loss in difficult to test people. Investigation of the reliability of the auditory steady-state response (ASSR) for measuring hearing thresholds in older adults is limited. This study aimed to investigate if ASSR can be a reliable, objective measure of frequency specific hearing thresholds in older adults. Hearing thresholds were tested at 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz in 50 participants aged between 60 and 85 years old, using automated PTA and ASSR. Hearing thresholds obtained from PTA and ASSR were found to be significantly correlated (p < .001) in a cohort consisting of participants with normal hearing or mild hearing loss. ASSR thresholds were significantly higher as compared to PTA thresholds, but for the majority of cases the difference remained within the clinically acceptable range (15 dB). This study provides some evidence to suggest that ASSR can be a valuable tool for estimating objective frequency-specific hearing thresholds in older adults and indicate that ASSR could be useful in creating hearing treatment plans for older adults who are unable to complete behavioral PTA. Further research on older adults is required to improve the methodological features of ASSR to increase consistency and reliability, as well as minimize some of the limitations associated with this technique.

Fish hearing and how it is best determined

Abstract Hearing, as defined by numerous investigators of vertebrate hearing, involves not only detection of a sound, but the ability to respond to the sound behaviourally. Thus, in order to understand what a fish (or any animal) hears, it is important to use behavioural methods that allow an animal to “tell the investigator” which sounds are detected and which are not. However, since the 1980’s, most studies that suggest they are measuring fish hearing have used electrophysiological approaches to measure the response of the ear or lower levels of the central auditory system to sounds. In this paper, we argue that these electrophysiological measures do not represent hearing since they do not indicate what sounds a fish can potentially respond to behaviourally. Thus, while the electrophysiological measures provide some useful and interesting insights into fish sound detection mechanisms, the most valid measures of hearing sensitivity, and understanding which sounds (anthropogenic or otherwise) that fish are able to respond to, are obtained using behavioural studies. We also argue that these studies must be done in carefully designed acoustic setups so that the nature of the stimulus to which the fish responds is appropriate and well understood.

Combining Cochlear Analysis and Auditory Evoked Potentials in a Beluga Whale With High-Frequency Hearing Loss.

Correlations between inner ear morphology and auditory sensitivity in the same individual are extremely difficult to obtain for stranded cetaceans. Animals in captivity and rehabilitation offer the opportunity to combine several techniques to study the auditory system and cases of hearing impairment in a controlled environment. Morphologic and auditory findings from two beluga whales (Delphinapterus leucas) in managed care are presented. Cochlear analysis of a 21-year-old beluga whale showed bilateral high-frequency hearing loss. Specifically, scanning electron microscopy of the left ear revealed sensory cell death in the first 4.9 mm of the base of the cochlea with scar formation. Immunofluorescence microscopy of the right ear confirmed the absence of hair cells and type I afferent innervation in the first 6.6 mm of the base of the cochlea, most likely due to an ischemia. Auditory evoked potentials (AEPs) measured 1.5 years prior this beluga's death showed a generalized hearing loss, being more pronounced in the high frequencies. This individual might have had a mixed hearing loss that would explain the generalized hearing impairment. Conversely, based on AEP evaluation, her mother had normal hearing and subsequent cochlear analysis did not feature any apparent sensorineural pathology. This is believed to be the first study to compare two cochlear analysis techniques and hearing sensitivity measurements from AEPs in cetaceans. The ability to combine morphological and auditory data is crucial to validate predictions of cochlear frequency maps based on morphological features. In addition, our study shows that these three complementary analysis techniques lead to comparable results, thus improving our understanding of how hearing impairment can be detected in stranding cases.

Auditory threshold in fishes: Towards international standard measurement procedures

Fish rely on their auditory system for survival to detect and interpret sounds in their surroundings, especially those originating from predators, prey, and conspecifics. The sensitivity of fish hearing can be impaired, for example, by masking or temporary threshold shifts. To understand and quantify the impact of noise in the oceans, we need a quantitative and comparable understanding of fishes’ impaired and unimpaired hearing sensitivities to sound pressure and sound particle motion. Historically, hearing sensitivities were measured to generate an audiogram for a fish species of interest. Therefore, audiograms are only available for a few individuals representing a few species. Crucially, differences between measurement protocols leave existing audiograms mostly incomparable. The goldfish (Carassius auratus) is a species for which many audiograms have been measured and the reported hearing thresholds exceed a 40 dB spread, largely attributed to differences in methodology rather than in hearing sensitivity [Ladich & Fay, 2013; Maruska & Sisneros, 2016]. These large differences indicate a need to harmonize measurement procedures. Standardization of hearing sensitivity measurements is therefore essential if we are to achieve environmental management goals in the United States, Europe, and worldwide. We propose a path that leads to the development of suitable international standards.

Selective Inner Hair Cell Dysfunction in Chinchillas Impairs Hearing-in-Noise in the Absence of Outer Hair Cell Loss.

Poorer hearing in the presence of background noise is a significant problem for the hearing impaired. Ototoxic drugs, ageing, and noise exposure can damage the sensory hair cells of the inner ear that are essential for normal hearing sensitivity. The relationship between outer hair cell (OHC) loss and progressively poorer hearing sensitivity in quiet or in competing background noise is supported by a number of human and animal studies. In contrast, the effect of moderate inner hair cell (IHC) loss or dysfunction shows almost no impact on behavioral measures of hearing sensitivity in quiet, when OHCs remain intact, but the relationship between selective IHC loss and hearing in noise remains relatively unknown. Here, a moderately high dose of carboplatin (75mg/kg) that produced IHC loss in chinchillas ranging from 40 to 80% had little effect on thresholds in quiet. However, when tested in the presence of competing broadband (BBN) or narrowband noise (NBN), thresholds increased significantly. IHC loss >60% increased signal-to-noise ratios (SNRs) for tones (500-11,300Hz) in competing BBN by 5-10dB and broadened the masking function under NBN. These data suggest that IHC loss or dysfunction may play a significant role in listening in noise independent of OHC integrity and that these deficits may be present even when thresholds in quiet are within normal limits.

Evaluating the Use of an Assistive Listening Device for Communication Efficiency Using the Diapix Task: A Pilot Study

Objective: The present study aimed to investigate the effects of assistive listening device (ALD) use on communication efficiency in groups of elderly adults with and without hearing impairment during a structured language sampling task. The relationship between self-perceived hearing handicap and communication efficiency was also explored. Method: Twenty-two subjects completed measures of hearing sensitivity, perceived hearing handicap, cognition, and a language sample. One half of the hearing-impaired participants and one half of the normal-hearing group were randomly assigned to use an ALD during a structured conversation task with a naïve partner. Results: The Hearing Loss/No ALD group had significantly more breakdowns than the Hearing Loss/With ALD group. Further, the Hearing Loss/With ALD group performed statistically similar to the two groups without hearing loss. For the normal-hearing groups as well as the Hearing Loss/No ALD group, self-perceived hearing handicap was significantly correlated with the number of communication breakdowns. Conclusion: The results lent preliminary support for the use of ALDs in the management of hearing loss. A case for functional assessment of communication was made to better illuminate causes of perceived communication handicap in the aural rehabilitation of elderly persons with hearing impairment.

California sea lion (Zalophus californianus) aerial hearing sensitivity measured using auditory steady-state response and psychophysical methods

Although electrophysiological methods of measuring the hearing sensitivity of pinnipeds are not yet as refined as those for dolphins and porpoises, they appear to be a promising supplement to traditional psychophysical procedures. In order to further standardize electrophysiological methods with pinnipeds, a within-subject comparison of psychophysical and auditory steady-state response (ASSR) measures of aerial hearing sensitivity was conducted with a 1.5-yr-old California sea lion. The psychophysical audiogram was similar to those previously reported for otariids, with a U-shape, and thresholds near 10 dB re 20 μPa at 8 and 16 kHz. ASSR thresholds measured using both single and multiple simultaneous amplitude-modulated tones closely reproduced the psychophysical audiogram, although the mean ASSR thresholds were elevated relative to psychophysical thresholds. Differences between psychophysical and ASSR thresholds were greatest at the low- and high-frequency ends of the audiogram. Thresholds measured using the multiple ASSR method were not different from those measured using the single ASSR method. The multiple ASSR method was more rapid than the single ASSR method, and allowed for threshold measurements at seven frequencies in less than 20 min. The multiple ASSR method may be especially advantageous for hearing sensitivity measurements with otariid subjects that are untrained for psychophysical procedures.

Aerial audiograms of Steller and California sea lions measured using auditory steady-state response methods.

Detection of aerial vocal signals by conspecifics is important in the reproductive behavior of the otariid pinnipeds. However, aerial hearing sensitivity measurements have only been obtained for a few otariid individuals that were trained to participate in behavioral experiments. In order to expand upon this small data set, auditory steady-state response (ASSR) methods were used to examine the aerial hearing sensitivity of Steller and California sea lions. Although ASSR thresholds were elevated relative to behavioral thresholds reported for otariids, the ASSR audiograms of the majority of individuals were similar to each other and to behavioral audiograms in terms of relative sensitivity. A marked reduction in sensitivity with increasing frequency regularly occurred between 16 and 32 kHz, indicating a consistent high-frequency cutoff. The reliability of the ASSR audiograms for both species suggests that behavioral aerial audiograms that exist for a few Steller and California sea lion individuals can be appropriately extrapolated to larger populations. The similarity of the ASSR audiograms among the Steller and California sea lions supports the notion that the otariid pinnipeds form a functional hearing group, with similar aerial hearing in terms of sensitivity and frequency range of hearing. [Work supported by ONR and NOAA Ocean Acoustics Program.]

A comparison of behavioral and electrophysiological measures of aerial hearing sensitivity in a Steller sea lion (Eumetopias jubatus).

A number of studies with odontocete cetaceans have demonstrated that hearing sensitivity measurements using electrophysiological auditory steady‐state responses (ASSRs) can provide an efficient means of estimating a subject’s behavioral audiogram. Expansion of ASSR methods to another marine mammal group, the otariid pinnipeds (sea lions and fur seals), holds the potential to increase the number of otariid individuals and species for which hearing sensitivity data are available. A within‐subject comparison of ASSR and behavioral measures of aerial hearing sensitivity was conducted with an individual of the largest otariid species, the Steller sea lion. Psychophysical methods were used to obtain an unmasked aerial audiogram at 13 frequencies spanning a range of 0.125 to 34 kHz. Corresponding ASSR thresholds measured at frequencies of 1, 2, 5, 10, 20, and 32 kHz had differences (relative to behavioral thresholds) ranging from 1 dB at 20 kHz to 30 dB at 1 kHz. Overall, the ASSR audiogram was a fairly accurate predictor of the behavioral audiogram at frequencies of 2 kHz and above. Our results suggest that ASSR methods can be appropriately applied to otariid pinnipeds in estimating aerial sensitivity at frequencies of approximately 2 kHz and above.

Inner ear anatomy is a proxy for deducing auditory capability and behaviour in reptiles and birds.

Inferences of hearing capabilities and audition-related behaviours in extinct reptiles and birds have previously been based on comparing cochlear duct dimensions with those of living species. However, the relationship between inner-ear bony anatomy and hearing ability or vocalization has never been tested rigorously in extant or fossil taxa. Here, micro-computed tomographic analysis is used to investigate whether simple endosseous cochlear duct (ECD) measurements can be fitted to models of hearing sensitivity, vocalization, sociality and environmental preference in 59 extant reptile and bird species, selected based on their vocalization ability. Length, rostrocaudal/mediolateral width and volume measurements were taken from ECD virtual endocasts and scaled to basicranial length. Multiple regression of these data with measures of hearing sensitivity, vocal complexity, sociality and environmental preference recovered positive correlations between ECD length and hearing range/mean frequency, vocal complexity, the behavioural traits of pair bonding and living in large aggregations, and a negative correlation between ECD length/rostrocaudal width and aquatic environments. No other dimensions correlated with these variables. Our results suggest that ECD length can be used to predict mean hearing frequency and range in fossil taxa, and that this measure may also predict vocal complexity and large group sociality given comprehensive datasets.

Unilateral Tinnitus Caused by Cerumen Impaction and Stochastic Resonance

Objectives: The objectives of this study were: (i) To investigate hearing lost in patients with tinnitus caused by cerumen impaction before and after cerumen removal and its relationship to the tinnitus. (ii) To discuss possible role of synaptic noise by mechanism of stochastic resonance. Methods: Nine patients, who had unilateral tinnitus and cerumen impaction, were selected for the study. Standard audiometric evaluation was performed, including case history, and measures of hearing sensitivity at 0.25-8 kHz. The testing protocol had three response tasks: threshold testing, loudness matching, and pitch matching. The time after cerumen removal to the end of tinnitus was measured. Results: In all patients the tinnitus disappeared in 20 minutes after cerumen removal. Control audiometry five minutes after cerumen removal showed recovery of normal hearing. Conclusion: Fast dissipation of tinnitus after cerumen removal and recovery of normal hearing shows possible connection between mechanism of weak signal enhancement for example by mechanism of stochastic resonance and tinnitus. Such a mechanism may also explain presence of tinnitus in individuals with intact auditory perception. Study conducted at Otorhinolaryngology Outpatient Clinic, Rychnov nad Kneznou The work has been supported by the research grant of the Faculty of Chemical Engineering of the Institute of Chemical Technology, Prague No. MSM 6046137306.

A portable system for marine mammal auditory-evoked potential measurements

Limitations to behavioral measures of hearing sensitivity in marine mammals include the time and expense typically required to train subjects. These limitations have resulted in limited subjects and lingering questions regarding intraspecific variability. An alternative to behavioral methods is the electrophysiological method, where passive electrodes are used to measure auditory-evoked potentials (AEPs) generated by the brain in response to sound stimuli. Marine mammal AEP measurements have been limited by the complexity of the technique and the limited applicability of commercially available AEP systems. In this paper, a portable, laptop computer-based system for marine mammal AEP measurements will be presented. The system features commercial off-the-shelf components, including a data acquisition PC card, biopotential amplifier, and programmable attenuator. The system is housed in a rugged, shock-resistant case. Custom software is used to present sound stimuli, record evoked responses, and analyze the resulting data. The system has been used to measure auditory brainstem responses to clicks and tone pips and envelope following responses to amplitude-modulated tones in bottlenose dolphins. Preliminary data obtained with the system will be presented and compared to behavioral hearing measures. [Work supported by the ILIR at SPAWARSYSCEN-SD and the ONR.]

Hearing loss, control, and demographic factors influencing hearing aid use among older adults.

Preference for non-use of hearing aids among older adults who are candidates for amplification remains to be explained. Clinical studies have examined the contribution of consumer attitudes, behaviors, and life circumstances to this phenomenon. The present study extends the interests of earlier investigators in that it examines psychological control tendencies in combination with hearing loss and demographic variables among older adults who elected to accept (adherents) or ignore (nonadherents) advice from hearing professionals to acquire and use hearing aids. One hundred thirty-one individuals participated by completing measures of hearing, hearing handicap, psychological control, depression, and ego strength. Participants were asked to provide demographic information and personal opinions regarding hearing aid use. Adherence group and gender differences were noted on measures of hearing sensitivity, psychological control, and demographic factors. Female adherents demonstrated greater hearing loss and poorer word recognition ability but less hearing handicap, higher internal locus of control, higher ego strength, and fewer depressive tendencies than female nonadherents. They reported demographic advantages. Female adherents assumed responsibility for effective communication. Although male adherents and nonadherents did not differ significantly demographically, male adherents were more accepting of their hearing loss, took responsibility for communication problems, and found hearing aids less stigmatizing. Implications for clinical practice and future clinical investigations are identified and discussed. Results are expected to be of interest to clinicians, clinical investigators, and health care policymakers.

Cochlear implantation: relationships with research on auditory deprivation and acclimatization.

This paper reviews research on cochlear implantation relevant to deprivation and acclimatization with acoustical hearing aids. The term "deprivation" is used in its everyday sense to refer to the bilateral absence of acoustic stimulation. Results are reviewed from several sources, with detailed evidence presented from three groups of postlingually deafened adult patients and one group of prelingually deafened child patients, all implanted at the University of Iowa. Outcomes from implantation reveal consistent effects of deprivation, evidenced by significant negative correlations between accuracy of speech perception and the duration of profound/total deafness before implantation. Outcomes also show acclimatization in the form of significant improvements in performance over time after implantation. For adult patients, the level of performance measured shortly after implantation on average is about half the level measured eventually. Individually, 80% of the adult patients implanted in Iowa show significant performance improvements with time. On average, performance reached asymptote after 30 to 40 mo of implant use, although individual differences in the rate and amount of improvement are large. Absolute accuracy of speech perception with implants by adults is believed to be related to preoperative measures in three domains: 1) the number and physiological responsiveness of auditory ganglion cells and nerve fibers, indexed by measures of hearing sensitivity, duration of deafness, and age; 2) the responsiveness of the central nervous system, indexed by measures of cognitive and linguistic ability, and possibly also by age and duration of deafness; and 3) the motivation to learn to use the implant. Preliminary analyses suggest that the measures in the first domain are more strongly associated with the immediate benefit from implantation than with the subsequent improvement in performance over time.

Anesthesia effects: auditory brain-stem response

Auditory brain-stem responses (ABRs) were measured in the awake state and with ketamine and xylazine anesthesia in adult gerbils. Surface recorded vertex-positive components of the ABR were analyzed with respect to the awake and anesthetized states as a function of stimulus frequency. ABR thresholds were not altered with ketamine/xylazine. Small increases in peak latency were associated with anesthesia for all components except wave P1. Increases in absolute latency were progressively greater for successive peaks, reaching an average shift of 0.41 msec for wave P6. Amplitude changes with anesthesia were more variable, with increases generally seen for waves P4 and P6. Significant anesthesia effects on peak latency and amplitude were independent of stimulus frequency. These data confirm previously reported ABR sensitivity to non-barbiturate anesthesia. Direct comparisons of ABR interpeak intervals or amplitude ratios from awake versus anesthetized animals must account for the effects of barbiturate and non-barbiturate agents. However, the stability of response threshold and the small magnitude of latency and amplitude changes with a ketamine and xylazine regimen demonstrate that accurate electrophysiological measures of hearing sensitivity and auditory brain-stem activity can be obtained in anesthetized animals, provided that temperature and other parameters are maintained within normal physiological limits.

Factors which affect measures of speech audibility with hearing aids.

Speech audibility may be defined as that proportion of a speech spectrum which is above a person's threshold. To optimize speech audibility with a hearing aid, several measures are needed. These include quantification of a speech spectrum, measures of hearing sensitivity, and measures of the "real ear" gain of the hearing aid. Some procedural factors must be considered to obtain adequate measures in a typical clinical setting. Those considered here are: (1) a modified Articulation Index to quantify a speech spectrum, (2) specification of hearing sensitivity with a narrowband sound field reference where the out-of-band rejection rate of the sound field stimulus is greater than twice the slope of the hearing loss, and (3) use of functional gain (measured directly or estimated using earphone and sound field results provided that the sound field stimulus has the required characteristics for measuring hearing sensitivity in the sound field) as a measure of the real ear gain of the hearing aid. Guidelines are given for the practical measurement of speech audibility in a typical clinical setting. The guidelines are appropriate for all measures of real ear gain including those obtained with all probe tube systems.