Greater Hearing Loss Research Articles

The Auditory Steady State Response in Individuals with Neurological Insult of the Central Auditory Nervous System

The auditory steady state response (ASSR) has recently gained attention with respect to estimates of hearing sensitivity and configuration of hearing loss. The present investigation compared behavioral thresholds to estimated ASSR thresholds in subjects with confirmed CANS lesions to determine if this population can be accurately evaluated with ASSR techniques. Comparisons were made between the experimental group and a normal control group matched for age and hearing sensitivity. ASSR thresholds were obtained for the carrier frequencies of 500 and 2000 Hz with a 46 Hz modulation rate and compared to behavioral thresholds. Within and between group comparisons were made. The control group demonstrated strong correlation between their behavioral and estimated ASSR thresholds which significantly contrasted the neurological group. Additionally, individuals with neurological impairment of the CANS exhibited elevated thresholds that were on average 24 dB greater at 2000 Hz than their behavioral thresholds. These results suggest that individuals with neurological insult may appear as hearing impaired or having greater hearing loss than is actually present. As a result, the ASSR may demonstrate the potential to assist in the detection of CANS dysfunction.

A Look at AR in the Last Decade

A Look at AR in the Last Decade

Correlation of hearing impairment with site of tympanic membrane perforation

Objective: This prospective study was done to assess the level of preoperative hearing impairment in different sites of pars tensa perforation in patients with chronic suppurative otitis media (CSOM) tubo-tympanic type undergoing myringoplasty. Materials and Methods: A total of 50 patients were recruited from the outpatient Department of Otorhinolaryngology and Head and Neck Surgery from June 2003 to May 2004. Cases of CSOM tubo-tympanic type with dry central perforation, with conductive type of hearing loss were subjected to myringoplasty. Preoperative audiometric evaluations were done. Just prior to operation, examination under microscope was performed. Exact site of perforation was noted. During operation, those found to have ossicular discontinuity or fixation were excluded from this study. Results: It was observed that the greatest hearing loss was found in big central (45dB) and posterior central (43dB); whereas least in those of anterior central (31dB) and central malleolar (34dB) perforations. The average hearing loss at 500Hz, 1000Hz and 2000Hzwas 46.40 dB, 30.90 dB and 31.9 dB respectively. This showed that the hearing loss is maximum at the lowest frequencies and minimum as the frequencies increase. Conclusion: This study shows that the posterior-central perforations cause more hearing loss than anterior-central ones. The hearing loss is maximum at the lowest frequencies and minimum as the frequencies increase. Journal of Institute of Medicine Vol.27(2) 2005

The effects of hearing loss on the contribution of high- and low-frequency speech information to speech understanding. II. Sloping hearing loss

The speech understanding of persons with sloping high-frequency (HF) hearing impairment (HI) was compared to normal hearing (NH) controls and previous research on persons with "flat" losses [Hornsby and Ricketts (2003). J. Acoust. Soc. Am. 113, 1706-1717] to examine how hearing loss configuration affects the contribution of speech information in various frequency regions. Speech understanding was assessed at multiple low- and high-pass filter cutoff frequencies. Crossover frequencies, defined as the cutoff frequencies at which low- and high-pass filtering yielded equivalent performance, were significantly lower for the sloping HI, compared to NH, group suggesting that HF HI limits the utility of HF speech information. Speech intelligibility index calculations suggest this limited utility was not due simply to reduced audibility but also to the negative effects of high presentation levels and a poorer-than-normal use of speech information in the frequency region with the greatest hearing loss (the HF regions). This deficit was comparable, however, to that seen in low-frequency regions of persons with similar HF thresholds and "flat" hearing losses suggesting that sensorineural HI results in a "uniform," rather than frequency-specific, deficit in speech understanding, at least for persons with HF thresholds up to 60-80 dB HL.

Effects of industrial solvents on hearing and balance: A review

Industrial hearing loss has generally been associated with noise exposure, but there is a growing awareness that industrial solvents can have an adverse effect on the auditory and vestibular systems in man. Both animal experiments and human studies point to an ototoxic effect of industrial solvents, as well as some central auditory and vestibular disturbances. This review examines the research from the last four decades in an attempt to get an overview of the available evidence. Research shows that industrial solvents are ototoxic in rats. The majority of the solvents studied cause a loss of auditory sensitivity in the mid-frequencies in rats, affecting outer hair cells in the order OHC 3 > OHC 2 > OHC 1 . Inner hair cells are generally unaffected. Spiral ganglion cells are most vulnerable to trichloroethylene. Simultaneous exposure to solvents and noise results in a synergistic effect; the pattern of trauma mirrors that due to solvent exposure rather than noise, but is more enhanced. There is a critical level when synergy occurs. The effects of solvents on the vestibular system are neurotoxic and influence the vestibulo-oculomotor system in both animals and humans; humans also present with problems in postural sway. There is a strong suggestion from human studies that solvents are ototoxic in man, but findings show that both the peripheral and central auditory pathways can be affected. Hearing losses can be in the high frequency region or can affect a wider range of frequencies. Hearing loss and balance disturbances can occur at levels below permitted levels of exposure. The synergistic effect of combined exposure to solvents and noise has also been noted in humans, resulting in greater hearing losses than would be expected from exposure to noise and solvents alone. The findings from both human and animal studies indicate that exposure to industrial solvents or to industrial solvents and noise can have an adverse effect on hearing and balance. The implications for industry and hearing conservation are far reaching.

A Multicenter Evaluation of How Many Infants With Permanent Hearing Loss Pass a Two-Stage Otoacoustic Emissions/Automated Auditory Brainstem Response Newborn Hearing Screening Protocol

Ninety percent of all newborns in the United States are now screened for hearing loss before they leave the hospital. Many hospitals use a 2-stage protocol for newborn hearing screening in which all infants are screened first with otoacoustic emissions (OAE). No additional testing is done with infants who pass the OAE, but infants who fail the OAE next are screened with automated auditory brainstem response (A-ABR). Infants who fail the A-ABR screening are referred for diagnostic testing to determine whether they have permanent hearing loss (PHL). Those who pass the A-ABR are considered at low risk for hearing loss and are not tested further. The objective of this multicenter study was to determine whether a substantial number of infants who fail the initial OAE and pass the A-ABR have PHL at approximately 9 months of age. Seven birthing centers with successful newborn hearing screening programs using a 2-stage OAE/A-ABR screening protocol participated. During the study period, 86634 infants were screened for hearing loss at these sites. Of those infants who failed the OAE but passed the A-ABR in at least 1 ear, 1524 were enrolled in the study. Data about prenatal, neonatal, and socioeconomic factors, plus hearing loss risk indicators, were collected for all enrolled infants. When the infants were an average of 9.7 months of age, diagnostic audiologic evaluations were done for 64% of the enrolled infants (1432 ears from 973 infants). Twenty-one infants (30 ears) who had failed the OAE but passed the A-ABR during the newborn hearing screening were identified with permanent bilateral or unilateral hearing loss. Twenty-three (77%) of the ears had mild hearing loss (average of 1 kHz, 2 kHz, and 4 kHz < or =40-decibel hearing level). Nine (43%) infants had bilateral as opposed to unilateral loss, and 18 (86%) infants had sensorineural as opposed to permanent conductive hearing loss. If all infants were screened for hearing loss using the 2-stage OAE/A-ABR newborn hearing screening protocol currently used in many hospitals, then approximately 23% of those with PHL at approximately 9 months of age would have passed the A-ABR. This happens in part because much of the A-ABR screening equipment in current use was designed to identify infants with moderate or greater hearing loss. Thus, program administrators should be certain that the screening program, equipment, and protocols are designed to identify the type of hearing loss targeted by their program. The results also show the need for continued surveillance of hearing status during childhood.

Heat shock factor 1-deficient mice exhibit decreased recovery of hearing following noise overstimulation

Heat shock proteins (Hsps) can enhance cell survival in response to stress. Heat shock factor 1 (Hsf1) is the major transcription factor that regulates stress-inducible Hsp expression. We previously demonstrated the presence of Hsf1 in the rodent cochlea and also demonstrated that a heat shock known to precondition the cochlea against noise trauma results in Hsf1 activation in the rodent cochlea. In the present study, we used an Hsf1-deficient (Hsf1-/- mouse model to determine whether eliminating the Hsf1-dependent stress pathway would influence hearing loss and/or recovery from a moderate-intensity noise. Hsf1-/- mice and their normal littermates (Hsf1+/+) were exposed to a 98-dB, broadband (2-20 kHz) noise for 2 hr, and auditory brainstem response thresholds were measured at three frequencies (4, 12, and 20 kHz) 3 hr, 3 days, and 2 weeks after noise. Hsf1-/- mice had greater hearing loss than Hsf1+/+ mice, with significant differences in recovery observed at all frequencies tested by 2 weeks after noise. Increased outer hair cell loss was also observed in Hsf1-/- mice following noise. These studies provide evidence for the importance of Hsf1 in cochlear protection, recovery, and/or repair following noise overstimulation.

Farm Noise Emissions During Common Agricultural Activities

Noise injury in agriculture is a significant yet often unrecognized problem. Many farmers, farm workers, and family members are exposed to noise levels above recommended levels and have greater hearing loss than their non-farming contemporaries. The aim of this study was to gather up-to-date information on farm noise levels and to enhance the quality of information available to assist farmers in reducing noise exposure and meeting Occupational Health and Safety (OHS) regulations regarding noise management. Farm visits were conducted on 48 agricultural establishments that produce a range of commodities. Noise levels were measured at the ears of operators and bystanders involved in typical activities on farms. The average and peak noise levels were measured for 56 types of machinery or sites of farming activity, totaling 298 separate items and activities. Common noise hazards identified included firearms, tractors without cabs, workshop tools, small motors (e.g., chainsaws, augers, pumps), manual handling of pigs, shearing sheds, older cabbed tractors, and heavy machinery such as harvesters, bulldozers, and cotton module presses. We found that use of firearms without hearing protection presents a pressing hearing health priority. However, farming activities involving machinery used for prolonged periods also present significant risks to farmers' hearing health. Noise management strategies on the farm are essential in order to prevent noise injury among farmers.

You don't hear with your ears

You don't hear with your ears

CHARGE Syndrome: A Window of Opportunity for Audiologic Intervention

To detail the clinical features of 22 new patients with a syndrome characterized by ocular coloboma, heart defects, atretic choanae, retarded growth or development, genital hypoplasia, and ear anomalies or hearing loss (CHARGE) seen in a tertiary academic medical center; compare auditory brainstem response (ABR) thresholds and behavioral hearing test results; identify a "window of opportunity" for audiologic intervention; review the literature regarding hearing results in CHARGE syndrome; and review the relationship between facial palsy and sensorineural hearing loss. Clinical data were gathered to examine 1) the variety of hearing results, 2) the average age at the time of hearing loss identification in 22 children with CHARGE using electrophysiologic and behavioral test methods, 3) the usefulness of the ABR as an early indicator of hearing sensitivity for a select group composed of children from the present study and from an earlier report from the same institution, and 4) the value of congenital facial paralysis as a predictor of sensorineural hearing loss in CHARGE children seen in the authors' institution since 1983. All children had 4 or more acronymic features, including colobomatous defects or choanal atresia. Ear anomalies/hearing loss occurred at least as frequently as other primary features. A total of 81% of patients had hearing loss; in this subset, 1 child had a mild degree of loss, and the remaining children had moderate or greater losses. The average age at which ABR confirmed hearing status was 3.8 months, whereas for behavioral testing, that age was 24.7 months, a statistically significant difference. In a select group of 16 children, no statistical differences existed when comparing threshold results of early electrophysiologic testing with behavioral test findings obtained at a later date. Contingency analysis suggests that congenital facial paralysis and sensorineural hearing loss are related. Hearing loss is prevalent in children with CHARGE syndrome. Within a wide range of results exists a propensity for moderate or greater hearing loss in children with sensorineural or mixed impairments. Congenital facial palsy seems to be a valid statistical predictor of sensorineural hearing loss and can be a useful device in audiologic decision making. A "window of opportunity" for audiologic intervention exists in the first few months of life. Primary care providers are encouraged to recognize the need for immediate, early audiologic referral of their patients suspected to have CHARGE. Evaluation of hearing sensitivity during infancy and, when appropriate, provision of amplification are important components in the process of auditory habilitation. These efforts are in keeping with various professional guidelines that call for early detection of hearing loss and subsequent prompt intervention to minimize effects on infant development.

Female MRL.MpJ- Fas lpr autoimmune mice have greater hearing loss than males

Although women make up approximately 60–70% of the patients with autoimmune hearing loss, little is known about the impact of gender on this cochlear disease. To explore this relationship of gender and autoimmune inner ear disease, an evaluation was made of cochlear function in male and female autoimmune MRL.MpJ- Fas lpr mice. Autoimmune disease and hearing loss onset occur at 3–4 months of age, so mice were tested with auditory brainstem response audiometry at 3, 6, and 9 months of age to identify potential gender differences in thresholds. Sera also were analyzed for differences in the autoimmune factors of immune complexes, anti-nuclear antibodies, and hematocrits. By 9 months of age the surviving mice showed a dramatic gender difference. Female mice had thresholds 25–45 dB higher than males at 4, 8, and 16 kHz, although male thresholds at 32 kHz had risen sufficiently to be statistically similar to those for females. No gender differences were seen in any of the systemic autoimmune factors. These findings of worse hearing in female autoimmune mice parallel a reported female preponderance in clinical immune hearing disorders. This potential gender influence in autoimmune inner ear disease must be better understood for effective evaluation and treatment of this disorder.

Detection and intensity discrimination of brief tones as a function of duration by hearing-impaired listeners

For normal listeners, difference limens for intensity (DLs) for Gaussian-shaped tone pulses are largest at medium pulse durations (corresponding to about five cycles of the tonal carrier) when the pedestals are 10 dB above threshold, either in quiet or in a pink noise background. One explanation for this is that worst performance occurs when the internal representation of the tone pulses is most compact in time and frequency, affording minimal opportunity for ‘multiple looks’ (Van Schijndel et al., J. Acoust. Soc. Am. 105 (1999) 3425–3435). However, the mid-duration worsening is largest for medium overall levels, suggesting an involvement of compression on the basilar membrane (BM), which is also greatest at medium levels (Baer et al., J. Acoust. Soc. Am. 106 (1999) 1907–1916). If this is so, the mid-duration worsening should be reduced when BM compression is reduced by outer hair cell damage. To test this, subjects with sensorineural hearing losses were tested using 1-kHz or 4-kHz Gaussian-shaped tone pulses, in quiet or in pink noise that raised thresholds by 10–20 dB. For subjects with mild losses, poorest performance was sometimes found for medium durations. For more severe losses, intensity DLs tended to improve monotonically or remain roughly constant with increasing duration. Performance overall tended to be better for subjects with greater hearing losses. The results are more consistent with an explanation based on BM compression than with an explanation based on multiple looks.

Using conjoint analysis to examine the importance of hearing aid attributes.

To introduce conjoint analysis (CA) as a method to explain choice decisions of hearing aid users and to measure the contributions of different hearing aid attributes involved. The study was conducted using CA, a method that is well established in marketing, but has not been used for hearing aid research. CA examines the contributions (importance) various attributes make to overall preference judgements. It is based on the premises that objects (i.e., hearing aids) can be described as different combinations of several attributes. The relative importance of the attributes is estimated from integral judgements of hypothetical hearing aids. The advantages of CA are a more realistic presentation of complete products instead of isolated attributes and the consideration of trade-offs between the features. The following attributes selected from 12 features in a prestudy were included in the application: speech perception in quiet, speech perception in noise, handling, sound quality, localization, and feedback. 93 randomly chosen experienced hearing aid wearers participated in the survey. It was found that the attributes concerning speech perception were by far most important. Speech discrimination in quiet and in noise were almost equally significant and contributed with 56% to the preference decisions of the subjects. The remaining attributes showed values in the range of 10% to 12%. When comparing various subgroups dependent on age, sex, hearing loss, satisfaction, etc., significant differences concerning the preferences were found. Elder and female subjects attached greater importance of the attribute "handling" whereas younger patients judged "speech in noise" more important. In general, subjects with greater hearing loss considered speech intelligibility in quiet to be more important than in noisy surroundings. Moreover, sound quality seems to be a significant indicator for satisfaction with the hearing aid. This study proposes CA as a survey technique to examine individual preferences for hearing aids. Several assumptions about the importance of hearing aid features for different groups of users could be confirmed quantitatively. Segmentation showed valid results depending on socio-demographic and user-specific parameters. The method used and the results are of interest for audiologists as well as the hearing aid industry. They provide valuable tools for future hearing aid design and should be considered in the development of self-assessment inventories.

発症後進行した突発性難聴

We analyzed 14 patients who showed a further progression of hearing loss after an initial examination of 214 patients with sudden deafness. They were divided into 2 groups based on the type of hearing loss progression. Group I consisted of six patients who displayed a rapid progression after increased hearing loss had begun. Group II consisted of eight patients who showed transient hearing improvement before an increase in hearing loss. The clinical features of the 14 patients were from a earlier visit to the clinics experiencing dizziness and/or vertigo with less recovery of hearing loss than the other patients. However, more than 60% of the 14 patients showed complete recovery or a marked hearing improvement. The predominant type of hearing loss was high tone loss at the initial audiological assessment in both groups. The flat type hearing loss was usually noted at the time when the patients experienced their greatest hearing loss. Although the details of the etiology of hearing loss progression remain unclear, group I was thought to be the slow type sudden deafness, whereas the deterioration of hearing loss in group II may be due to a circulatory disturbance of the inner ear.

Hearing screening for school children with otitis media using otoacoustic emission measures

This study aimed to investigate the feasibility of using a technique other than pure-tone screening audiometry for the identification of slight or greater hearing loss in an urban population of indigenous Australian primary school children. Indigenous children have a higher prevalence of conductive hearing loss, associated with otitis media, than non-indigenous children in the same schools. Transient otoacoustic emission procedures were used as an alternative identification technique to pure tone screening audiometry. The otoacoustic emission results were compared with pure tone audiometry findings for the 150 Aboriginal and Torres Strait Islander children involved in the study. Comparison was made with pure tone audiometry for otoacoustic emission screening accuracy (in determining hearing loss >15 dB HL average) and also test practicality in urban school environments. Transient otoacoustic emission recording was found to show potential as a means of identifying slight or greater levels of hearing loss in a school environment. Test time was typically brief (less than 2 minutes per ear) and child acceptance of the otoacoustic emission procedure was good. Screening accuracy varied greatly with pass/fail criterion used, ranging from 16.2% to 83.8% sensitivity and from 20.7% to 93.1% specificity. With further development, transient otoacoustic emission screening techniques may reach a level of accuracy where such a procedure could be used as an alternative to traditional pure tone audiometric screening.

Hearing Loss Prevalence and Risk Factors Among Sierra Leonean Children

To determine hearing loss prevalence among a group of Third World children, to describe the physical examination and audiometric findings in the hearing-impaired children, and to assess the association of hearing loss with several known risk factors. It was hypothesized that chronic otorrhea would be the risk factor most strongly associated with hearing loss. Community screening program to identify and evaluate hearing-impaired children. Case-control analysis of hearing loss risk factors. A survey taker, blinded to the children's hearing status, ascertained risk factors. Rural community in eastern province of Sierra Leone, West Africa. Population-based sample of 2015 children aged 5 to 15 years. Risk factor analysis was performed in 184 children and an equal number of matched controls. Hearing loss determined according to World Health Organization, Geneva, Switzerland, definition. A total of 184 (9.1%) of 2015 children were found to have mild or greater hearing loss. The prevalence of bilateral profound hearing impairment was 4.0 per 1000. We assessed physical examination and audiometric findings. The risk factor most strongly associated with hearing loss was a history of otorrhea persisting longer than 1 month (odds ratio, 23.3; 95% confidence limits, 12.11, 45.40). A high prevalence of hearing loss was identified. Much of this impairment may result from chronic untreated or unrecognized ear infections. Further community-based studies of hearing-impaired children are necessary for planning preventive and curative programs.

Acoustic-Phonetic Context Considerations for Speech Recognition Testing of Hearing-Impaired Listeners

To test for differences in the identification of consonants in carrier sentences versus in VCVs extracted from the sentences, as a function of listeners' hearing-loss categories: moderate, severe, profound. To examine whether pauses inserted in the sentences will facilitate identification of the consonants. Voiced stops and fricatives were identified by 11 listeners with moderate hearing losses and by 7 listeners with severe losses (between subjects design) for the conditions of consonants in sentences and in VCVs extracted from the sentences (repeated measures). Nine of these listeners also identified the consonants in the sentences with pauses. Six normal-hearing listeners were tested for the consonants in the extracted VCVs and the sentences. Voiceless stops and fricatives were identified by 4 listeners with profound losses, 18 with severe losses, and 8 with moderate losses (between subjects) for the conditions of extracted VCVs and the sentences (repeated measures). All listeners were selected on the basis of their hearing levels. The listeners with moderate to severe hearing loss identified the voiced stops and fricatives more poorly when the syllables were in the carrier sentences than when extracted. Insertion of the pauses in the sentence did not improve performance significantly. The normal hearing listeners showed no differences in consonant identification between the two conditions, perhaps due to "ceiling effects". The voiceless stops and fricatives were also identified more poorly when in the extracted VCVs than in the carrier sentences by other listeners with moderate to profound hearing loss. Listeners with moderate or greater hearing loss can show poorer identification of consonants that are embedded midway in carrier sentences than when the acoustically identical consonants are in VCVs extracted from the sentences. The performance reduction for the consonants in sentences is not relieved from insertion of brief artificial pauses in the sentences. Further research is needed determine whether hearing-impaired listeners' identification of consonants in target words of clinical word recognition tests is facilitated when the words are extracted from carrier phrases.

Oto-traumatic effects of computer simulated magnetic coil impulse noise: analysis of mechanisms.

The brief impulse noise artifacts of 1.0 ms or less generated by some magnetic coils used in extracranial magnetic stimulation may induce acoustic trauma. We investigated the effects of these magnetic coil acoustic artifacts (MCAA) on the inner ear by exposing rabbits to computer stimulated impulse noise designed to mimic the impulse noise of the coil in spectrum and acoustic energy. The simulated impulse noise stimuli (50 impulses) were varied in maximum peak sound pressure (160, 157, and 155 dB re: 20 muPascal), rise-time (100 microseconds and 1,000 microseconds) and duration. The frequency spectrum of the simulated impulse noises were kept constant at 0.5 kHz to 7 kHz with peak energy in the 2-5 kHz range. The results indicated that the simulated magnetic coil impulse noise caused extensive cochlear damage and permanent threshold shifts largely equal to those induced by the MCAA. The MCAA created slightly greater PTS than the simulated impulse of the same peak sound pressure. Each of the 3 experimental stimuli induced similar PTS in the auditory range of 0.5 to 16 kHz, with the higher peak sound pressure stimuli (157 and 160 dB) causing greatest hearing loss. Increasing the rise-time of the simulated brief impulse noise from 100 microseconds to 1,000 microseconds did not reduce the level of PTS significantly. The results suggest that for brief acoustic signals of around 1 ms or less, the peak pressure and spectral content rather than the rise-time and duration were the important factors in the development of noise-induced hearing loss.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of Submaximal Exercise and Noise Exposure on Hearing Loss

A recent Scandinavian study reported that persons cycling at moderate intensity for 10 min suffered hearing loss when the exercise was accompanied by noise. The noise consisted of a 1/3 octave band-filtered noise with a 2000 Hz center frequency at 104 dB SPL. In the present study, adults cycled at 50 rev.min-1 against a force that elicited an oxygen cost equal to 70% of VO2max--an intensity frequently recommended in exercise prescriptions--with and without noise administered via headphones. Repeated measures ANOVA with three factors revealed that although a temporary hearing loss occurred following exercise-and-noise, a similar and slightly greater hearing loss occurred following noise-only. Hearing sensitivity was not significantly altered by exercise-only (p greater than .05). In general, hearing loss values were greatest between 3000 and 4000 Hz. In conclusion, temporary hearing loss was driven by noise exposure, not exercise. However, persons who choose to exercise with personal headphones or in a noisy environment should be aware of potential premature hearing loss.

Recognition of synthetic speech by hearing-impaired elderly listeners.

The Modified Rhyme Test (MRT), recorded using natural speech and two forms of synthetic speech, DECtalk and Votrax, was used to measure both open-set and closed-set speech-recognition performance. Performance of hearing-impaired elderly listeners was compared to two groups of young normal-hearing adults, one listening in quiet, and the other listening in a background of spectrally shaped noise designed to simulate the peripheral hearing loss of the elderly. Votrax synthetic speech yielded significant decrements in speech recognition compared to either natural or DECtalk synthetic speech for all three subject groups. There were no differences in performance between natural speech and DECtalk speech for the elderly hearing-impaired listeners or the young listeners with simulated hearing loss. The normal-hearing young adults listening in quiet out-performed both of the other groups, but there were no differences in performance between the young listeners with simulated hearing loss and the elderly hearing-impaired listeners. When the closed-set identification of synthetic speech was compared to its open-set recognition, the hearing-impaired elderly gained as much from the reduction in stimulus/response uncertainty as the two younger groups. Finally, among the elderly hearing-impaired listeners, speech-recognition performance was correlated negatively with hearing sensitivity, but scores were correlated positively among the different talker conditions. Those listeners with the greatest hearing loss had the most difficulty understanding speech and those having the most trouble understanding natural speech also had the greatest difficulty with synthetic speech.