Selective attention in normal and impaired hearing

A common complaint among listeners with hearing loss (HL) is that they have difficulty communicating in common social settings. This article reviews how normal-hearing listeners cope in such settings, especially how they focus attention on a source of interest. Results of experiments with normal-hearing listeners suggest that the ability to selectively attend depends on the ability to analyze the acoustic scene and to form perceptual auditory objects properly. Unfortunately, sound features important for auditory object formation may not be robustly encoded in the auditory periphery of HL listeners. In turn, impaired auditory object formation may interfere with the ability to filter out competing sound sources. Peripheral degradations are also likely to reduce the salience of higher-order auditory cues such as location, pitch, and timbre, which enable normal-hearing listeners to select a desired sound source out of a sound mixture. Degraded peripheral processing is also likely to increase the time required to form auditory objects and focus selective attention so that listeners with HL lose the ability to switch attention rapidly (a skill that is particularly important when trying to participate in a lively conversation). Finally, peripheral deficits may interfere with strategies that normal-hearing listeners employ in complex acoustic settings, including the use of memory to fill in bits of the conversation that are missed. Thus, peripheral hearing deficits are likely to cause a number of interrelated problems that challenge the ability of HL listeners to communicate in social settings requiring selective attention.     

The role of spectral and temporal cues in vowel identification by listeners with impaired hearing.

This study examined the use of duration and formant frequency in the labeling of synthetic CVC stimuli forming a beet-bit continuum. Durational and F2 frequency cues to vowel identity varied systematically across stimuli. Subjects with normal hearing tended to rely primarily on F2 frequency in vowel labeling, whereas subjects with impaired hearing relied less on F2 information. This group difference was observed even for stimuli with large F2 differences, which were easily discriminated by all subjects. The effect of vowel duration on labeling was similar for both groups, with long-duration stimuli receiving more "beet" responses than short-duration stimuli across the F2 range. Psychoacoustic measures of frequency resolution and temporal resolution were poor predictors of a subject's use of formant information and duration information in labeling.     

Across-frequency comparison of temporal speech information by listeners with normal and impaired hearing.

Listeners with normal hearing (NH) and with sensorineural hearing impairment (HI) were tested on a speech-recognition task requiring across-frequency integration of temporal speech information. Listeners with NH correctly identified a majority of key words in everyday sentences when presented with a synchronous pair of speech-modulated tones at 750 and 3,000 Hz. They could tolerate small amounts (12.5 ms) of across-frequency asynchrony, but performance fell as the delay between bands was increased to 100 ms. Listeners with HI performed more poorly than those with NH when presented with synchronous across-frequency information. Further, performance of listeners with HI fell as a function of asynchrony more steeply than that of their NH counterparts. These results suggest that listeners with HI have particular difficulty comparing and effectively processing temporal speech information at different frequencies. The increased influence of asynchrony indicates that these listeners are especially hindered by slight disruptions in across-frequency information, which implies a less robust comparison mechanism. The results could not be attributed to differences in signal or sensation level, or in listener age, but instead appear to be related to the degree of hearing loss. This across-frequency deficit is unlikely to be attributed to known processing difficulties and may exist in addition to other known disruptions.     

Diotic loudness summation in normal and impaired hearing

Diotic loudness summation at 500 and 2000 Hz was measured in 10 normal-hearing and 10 cochlear-impaired listeners. Diotic stimuli were matched in loudness to monaural "standards" of 70, 80, and 90 dB SPL. Diotic loudness summation averaged about 9 dB at 500 Hz for both groups. At 2000 Hz, the hearing-impaired listeners showed reduced diotic loudness summation at the 70-and 80-dB levels, but showed normal diotic loudness summation (about 9 dB) at the 90-dB level. The results indicate that diotic loudness summation is normal in cochlear-impaired ears, provided that the stimuli are presented sufficiently above threshold.     

Diurnal changes in differential sensitivity and temporal resolution in morning-type and evening-type individuals with normal hearing

The present study attempts to determine diurnal changes by testing the differential sensitivity and temporal resolution in morning-type, evening-type, and intermediate-type individuals with normal hearing. Thirty participants with normal hearing were divided into morning-type, evening-type, and intermediate-type using “Morningness–Eveningness Questionnaire”. The tests of differential sensitivity and temporal resolution were administered to all the participants in the morning and evening, respectively. The differences in the test results between different timing across all the three groups were analyzed. The results of the study showed that there was a significant diurnal effect on psychoacoustic tests as morning-type individuals performed better when tested in morning and evening-type performed better when they were tested in evening. However, there was no diurnal effect found in intermediate group. The lack of inhibitory control and poor cognitive load in off peak time could have lead to poor scores. Thus, the variable of diurnal effects should be considered in further studies on psychoacoustic tests, especially in young adults. Furthermore, studies could be performed to explore diurnal effects on objective audiological tests in a larger group of population in the future.     

Binaural gap duration discrimination in listeners with impaired hearing and normal hearing

OBJECTIVE: This study was designed to measure the ability of listeners with and without sensorineural hearing loss to discriminate silent gaps between noise band markers of different frequencies presented in an anechoic and a reverberant listening environment. DESIGN: A two-interval, two-alternative, forced-choice paradigm was used to measure gap discrimination ability for six listeners with normal-hearing and six listeners with sensorineural hearing impairment. Marker stimuli were narrow bands of noise centered at frequencies from 500 to 7000 Hz. The center frequency of the leading marker was held constant at 2000 Hz and the center frequency of the trailing marker was varied randomly across runs. Stimuli were presented in two virtual listening environments (anechoic and reverberant). The listeners' task was to indicate which interval contained the marker pair separated by the larger silent gap. Gap discrimination was measured as a function of the center frequency of the trailing marker and as a function of listening environment. RESULTS: Gap discrimination thresholds (msec) varied as a function of the center frequency of the trailing marker. As the trailing marker frequency increased above and decreased below the leading marker frequency (2000 Hz), gap thresholds increased significantly. Hearing loss and listening environment did not have a significant effect on gap discrimination thresholds. Analysis of the gap discrimination functions revealed significantly steeper slopes for trailing marker frequencies below 2000 Hz than for trailing marker frequencies above 2000 Hz. A possible age effect was observed in the data and significant correlations were found between age and function slopes for several conditions. CONCLUSIONS: Gap discrimination becomes more difficult as the frequency disparity between leading and trailing noise bands increases. This pattern of results occurs independent of hearing loss but may be influenced by listener age.     

Auditory processing efficiency and temporal resolution in children and adults.

Children have higher auditory backward masking (BM) thresholds than adults. One explanation for this is poor temporal resolution, resulting in difficulty separating brief or rapidly presented sounds. This implies that the auditory temporal window is broader in children than in adults. Alternatively, elevated BM thresholds in children may indicate poor processing efficiency. In this case, children would need a higher signal-to-masker ratio than adults to detect the presence of a signal. This would result in poor performance on a number of psychoacoustic tasks but would be particularly marked in BM due to the compressive nonlinearity of the basilar membrane. The objective of the present study was to examine the competing hypotheses of "temporal resolution" and "efficiency" by measuring BM as a function of signal-to-masker interval in children and adults. The children had significantly higher thresholds than the adults at each of the intervals. Subsequent modeling and analyses showed that the data for both children and adults were best fitted using the same, fixed temporal window. Therefore, the differences in BM threshold between adults and children were not due to differences in temporal resolution but to reduced detection efficiency in the children.     

Auditory brainstem responses and usefulness of hearing aids in hearing impaired children with Cornelia de Lange syndrome

OBJECTIVE: To examine auditory brainstem evoked responses (ABRs) of children with Cornelia de Lange syndrome (CDLS) to evaluate hearing and the utility of hearing aids in hearing impaired cases. SUBJECTS AND METHODS: Thirteen Japanese infants and children with CDLS were studied. Behavioral observation audiometry and ABR were used to evaluate hearing. RESULT: Four different ABR patterns at 85 dB clicks were observed: no response in either ear (6 patients); clear ABRs in both ears (2 patients); no response in one ear but ABRs recorded in the other ear (3 patients); and no peaks after wave III in one ear and ABRs recorded in the other ear (2 patients). However, in 2 patients with no response in either ear at the first measurement, ABRs were recorded in one ear within 2 years. Three out of 13 patients exhibited better responses to sound through the use of hearing aids and auditory training. CONCLUSIONS: The fitting of hearing aids and early consistent training have a significant effect on auditory development in CDLS children in terms of making them aware of sound localization and the different types of environmental sound.     

Nonlinear properties of otoacoustic emissions in normal and impaired hearing

Click-evoked otoacoustic emissions (CEOAEs) exhibit nonlinearities in amplitude and time domains. The first objective of this study was to investigate whether there is any correlation between the temporal and amplitude nonlinearities of CEOAEs in normals. Additionally there is evidence that pathology affects the normal cochlear nonlinearity. The second objective was to investigate whether pathology affects the temporal nonlinear components. Conventional and maximum length sequence (MLS) CEOAEs were recorded in normal subjects and in patients with mild hearing loss. The slope of the input-output (I/O) function of the conventional CEOAE measured the amplitude nonlinearity. Two measures of temporal nonlinearity were the magnitude of the suppression that occurs with increase in stimulus rate and the amplitudes of the second and third order temporal interaction components (Volterra slices). The amplitude nonlinearity is well correlated with both the magnitude of the rate suppression and the amplitudes of the Volterra slices. The 'linear' CEOAE amplitude showed no differences between the normal and patient groups but the differences in the Volterra slices were substantial. This suggests that the first sign of damage to the cochlea is that the system becomes more linear. Hence the Volterra slices may provide a sensitive measure of cochlear damage.     

Evoked otoacoustic emissions in normal and hearing impaired adults and children

In adults and children, 203 normal ears, 124 cars with hearing-impairment and 37 ears with middle ear problems were studied concerning click-evoked oto-acoustic emissions. According to the results, this method by high specifity and sensitivity renders possible the recognition of low sensory hearing losses. Complete middle ear effusions too make themselves conspicuous by preventing the reception of these responses. The recording of click-evoked oto-acoustic emissions is a most promising auditory screening-method. A general use could essentially improve the early detection of hearing losses in infants. Additionally, in the pedaudiologic practice possibilities are indicated to employ this technique as a topodiagnostic instrument.     

Modulation detection interference in listeners with normal and impaired hearing.

Listeners were asked to detect amplitude modulation (AM) of a target (or signal) carrier that was presented in isolation or in the presence of an additional (masker) carrier. The signal was modulated at a rate of 10 Hz, and the masker was unmodulated or was modulated at a rate of 2, 10, or 40 Hz. Nine listeners had normal hearing, 4 had a bilateral hearing loss, and 4 had a unilateral hearing loss; those with a unilateral loss were tested in both ears. The listeners with a hearing loss had normal hearing at 1 kHz and a 30- to 40-dB loss at 4 kHz. The carrier frequencies were 984 and 3952 Hz. In one set of conditions, the lower frequency carrier was the signal and the higher frequency carrier was the masker. In the other set, the reverse was true. For the impaired ears, the carriers were presented at 70 dB SPL. For the normal ears, either the carriers were both presented at 70 dB SPL or the higher frequency carrier was reduced to 40 dB SPL to simulate the lower sensation level experienced by the impaired ears. There was considerable individual variability in the results, and there was no clear effect of hearing loss. These results suggest that a mild, presumably cochlear hearing loss does not affect the ability to process AM in one frequency region in the presence of competing AM from another region.     

Frequency selectivity and temporal resolution in normal and hearing-impaired listeners

Methods of measuring the frequency selectivity of the auditory system using masking techniques are outlined and described in terms of the concept of the auditory filter. The relationship between the auditory filter shape and excitation patterns is described. Evidence is reviewed showing that frequency selectivity is usually reduced in people with cochlear hearing losses. Methods of measuring the temporal resolution of the auditory system are also reviewed, and results are compared for normally hearing and hearing-impaired subjects. Temporal resolution is impaired in most but not all cases of sensorineural hearing loss. It is concluded that the loss of frequency and temporal resolution accompanying cochlear hearing loss is a major cause of the difficulties encountered by the hearing impaired in understanding speech in noisy situations.     

Validation of the LittlEARS Auditory Questionnaire in children with normal hearing

Objectives

With more children receiving cochlear implants during infancy, there is a need for validated assessments of pre-verbal and early verbal auditory skills. The LittlEARS^® Auditory Questionnaire is presented here as the first module of the LittlEARS^® test battery. The LittlEARS^® Auditory Questionnaire was developed and piloted to assess the auditory behaviour of normal hearing children and hearing impaired children who receive a cochlear implant or hearing aid prior to 24 months of age. This paper presents results from two studies: one validating the LittlEARS^® Auditory Questionnaire on children with normal hearing who are German speaking and a second validating the norm curves found after adaptation and administration of the questionnaire to children with normal hearing in 15 different languages.

Methods

Scores from a group of 218 German and Austrian children with normal hearing between 5 days and 24 months of age were used to create a norm curve. The questionnaire was adapted from the German original into English and then 15 other languages to date. Regression curves were found based on parental responses from 3309 normal hearing infants and toddlers. Curves for each language were compared to the original German validation curve.

Results

The results of the first study were a norm curve which reflects the age-dependence of auditory behaviour, reliability and homogeneity as a measure of auditory behaviour, and calculations of expected and critical values as a function of age. Results of the second study show that the regression curves found for all the adapted languages are essentially equal to the German norm curve, as no statistically significant differences were found.

Conclusions

The LittlEARS^® Auditory Questionnaire is a valid, language-independent tool for assessing the early auditory behaviour of infants and toddlers with normal hearing. The results of this study suggest that the LittlEARS^® Auditory Questionnaire could also be very useful for documenting children's progress with their current amplification, providing evidence of the need for implantation, or highlighting the need for follow-up in other developmental areas.     

听障婴幼儿听觉干预后短期听觉语言能力评估

目的探讨不同助听设备及康复时间与听障婴幼儿听觉语言能力的关系,初步分析国内研发的评估方法与国际通用评估方法的关系。方法共选取47例13-36月龄重度或极重度感音神经性聋婴幼儿为观察对象,按助听设备类型将其分为助听器组(25例)与人工耳蜗组(22例),采用《听力障碍儿童听觉、语言能力评估标准及方法》分别在听觉干预的不同阶段(听觉干预0个月、3个月、6个月、9个月和12个月)评估受试者言语听觉能力与语言能力,同时通过问卷方式获得其听觉行为分级标准(categories of au-ditory performance,CAP)、言语可懂度分级标准(speech intelligibility rating,SIR)、婴幼儿有意义听觉整合量表(infant-toddler meaningful auditory integration scale,IT-MAIS)、有意义言语使用量表(meaningful use ofspeech scale,MUSS)和《小龄儿童听觉发展问卷》(Littl EARS Auditory Questionnaire)得分。结果经重复测量方差分析显示,随着听觉干预时间的推移,重度或极重度感音神经性聋婴幼儿言语听觉和语言能力逐渐提高。助听器组和人工耳蜗组在一年内言语听觉和语言能力差异无统计学意义。运用相关性分析得知,言语识别率与CAP、IT-MAIS和Littl EARS得分之间分别具有显著的线性相关,语言年龄与SIR得分之间有显著的线性相关,与MUSS得分之间无显著的线性相关。结论重度或极重度感音神经性聋婴幼儿助听听阈进入言语香蕉图范围的前提下,助听设备对其一年内言语听觉和语言能力的影响不存在差异。国内研发的评估方法与国际通用评估方法有一定程度的关联,可互为参考,但不可完全相互替代。     

Auditory brainstem responses predict auditory nerve fiber thresholds and frequency selectivity in hearing impaired chinchillas

Noninvasive auditory brainstem responses (ABRs) are commonly used to assess cochlear pathology in both clinical and research environments. In the current study, we evaluated the relationship between ABR characteristics and more direct measures of cochlear function. We recorded ABRs and auditory nerve (AN) single-unit responses in seven chinchillas with noise-induced hearing loss. ABRs were recorded for 1-8 kHz tone burst stimuli both before and several weeks after 4 h of exposure to a 115 dB SPL, 50 Hz band of noise with a center frequency of 2 kHz. Shifts in ABR characteristics (threshold, wave I amplitude, and wave I latency) following hearing loss were compared to AN-fiber tuning curve properties (threshold and frequency selectivity) in the same animals. As expected, noise exposure generally resulted in an increase in ABR threshold and decrease in wave I amplitude at equal SPL. Wave I amplitude at equal sensation level (SL), however, was similar before and after noise exposure. In addition, noise exposure resulted in decreases in ABR wave I latency at equal SL and, to a lesser extent, at equal SPL. The shifts in ABR characteristics were significantly related to AN-fiber tuning curve properties in the same animal at the same frequency. Larger shifts in ABR thresholds and ABR wave I amplitude at equal SPL were associated with greater AN threshold elevation. Larger reductions in ABR wave I latency at equal SL, on the other hand, were associated with greater loss of AN frequency selectivity. This result is consistent with linear systems theory, which predicts shorter time delays for broader peripheral frequency tuning. Taken together with other studies, our results affirm that ABR thresholds and wave I amplitude provide useful estimates of cochlear sensitivity. Furthermore, comparisons of ABR wave I latency to normative data at the same SL may prove useful for detecting and characterizing loss of cochlear frequency selectivity.