Exploring Use of the Coordinate Response Measure in a Multitalker Babble Paradigm.

Purpose: Three experiments examined the use of competing coordinate response measure (CRM) sentences as a multitalker babble. Method: In Experiment I, young adults with normal hearing listened to a CRM target sentence in the presence of 2, 4, or 6 competing CRM sentences with synchronous or asynchronous onsets. In Experiment II, the condition with 6 competing sentences was explored further. Three stimulus conditions (6 talkers saying same sentence, 1 talker producing 6 different sentences, and 6 talkers each saying a different sentence) were evaluated with different methods of presentation. Experiment III examined the performance of older adults with hearing impairment in a subset of conditions from Experiment II. Results: In Experiment I, performance declined with increasing numbers of talkers and improved with asynchronous sentence onsets. Experiment II identified conditions under which an increase in the number of talkers led to better performance. In Experiment III, the relative effects of the number of talkers, messages, and onset asynchrony were the same for young and older listeners. Conclusions: Multitalker babble composed of CRM sentences has masking properties similar to other types of multitalker babble. However, when the number of different talkers and messages are varied independently, performance is best with more talkers and fewer messages.

The effects of dosage and duration of auditory training for older adults with hearing impairment.

This study explored a range of training dosages and durations for a word-based auditory-training procedure for older adults with hearing impairment. Three groups received a different "dose": 2x/week; 3x/week; no training. Fifteen training sessions comprised a "cycle" which was repeated three times for each dosage. Groups that completed training performed significantly better than controls for speech-in-noise materials included in the training regimen, with no significant difference observed between the 2x or 3x/week training groups. Based on these results, as well as prior literature on learning theory, training 2x or 3x/week for 5-15 weeks appears to be sufficient to yield training benefits with this training regimen.

Telephone screening tests for functionally impaired hearing: current use in seven countries and development of a US version.

BACKGROUND: An estimated 36 million US citizens have impaired hearing, but nearly half of them have never had a hearing test. As noted by a recent National Institutes of Health/National Institute on Deafness and Other Communication Disorders (NIH/NIDCD) Working Group, "In the United States (in contrast to many other nations) there are no readily accessible low cost hearing screening programs…" (Donahue et al, 2010, p. 2). Since 2004, telephone administered screening tests utilizing three-digit sequences presented in noise have been developed, validated, and implemented in seven countries. Each of these tests has been based on a test protocol conceived by Smits and colleagues in The Netherlands. PURPOSE: Investigators from Communication Disorders Technology, Inc., Indiana University, and VU University Medical Center of Amsterdam agreed to collaborate in the development and validation of a screening test for hearing impairment suitable for delivery over the telephone, for use in the United States. This test, utilizing spoken three-digit sequences (triplets), was to be based on the design of Smits and his colleagues. RESEARCH DESIGN: A version of the digits-in-noise test was developed utilizing digit triplets spoken in Middle American dialect. The stimuli were individually adjusted to speech-to-noise ratio (SNR) values yielding 50% correct identification, on the basis of data collected from a group of 10 young adult listeners with normal hearing. A final set of 64 homogeneous stimuli were selected from an original 160 recorded triplets. Each test consisted of a series of 40 triplets drawn at random, presented in a noise background. The SNR threshold for 50% correct identification of the triplets was determined by a one-down, one-up adaptive procedure. The test was implemented by telephone, and administered to listeners with varying levels of hearing impairment. The listeners were then evaluated with pure-tone tests and other audiometric measures as clinically appropriate. STUDY SAMPLE: Ninety participants included 72 who were volunteers from the regular client population at the Indiana University Hearing Clinic, and 18 who were recruited with a newspaper ad offering a free hearing test. Of the 90 participants, 49 were later determined to have mean pure-tone thresholds greater than 20 dB hearing level (HL). DATA COLLECTION AND ANALYSIS: The primary data analyses were correlations between telephone test thresholds and other measures, including pure-tone thresholds and speech recognition tests, collected for the same participants. RESULTS: The correlation between the telephone test and pure-tone thresholds (r = 0.74) was within the range of correlations observed with successful telephone screening tests in use in other countries. Thresholds based on the average of only 21 trials (trials five through 25 of the 40-trial tracking history) yielded sensitivity and specificity values of 0.80 and 0.83, respectively, using pure-tone average((0.5, 1.0, 2.0 kHz)) >20 dB HL as the criterion measure. CONCLUSIONS: This US version of the digits-in-noise telephone screening test is sufficiently valid to be implemented for use by the general public. Its properties are quite similar to those telephone screening tests currently in use in most European countries. Telephone tests provide efficient, easy to use, and valid screening for functional hearing impairment. The results of this test are a reasonable basis for advising those who fail to seek a comprehensive hearing evaluation by an audiologist.

The relative importance of consonant and vowel segments to the recognition of words and sentences: effects of age and hearing loss.

This study investigated the ability to use cues contained within vowel and consonant segments by older listeners with normal or impaired hearing. Spectral shaping restored audibility for the hearing-impaired group. Word and sentence materials were processed to contain primarily consonants or vowels by replacing segments with low-level speech-shaped noise. The proportion of the total duration of preserved speech was varied by manipulating the amount of transitional information contained within vowel and consonant segments. Older listeners performed more poorly than young listeners on all conditions except when listening to sentences with only the vowels preserved. Results confirmed a greater contribution to intelligibility of vowel segments in sentences, but not in words, for young normal-hearing, older normal-hearing, and older hearing-impaired listeners. Older listeners received a greater benefit than young listeners from vowels presented in a sentence context. Correlation analyses among the older listeners demonstrated an association between consonant and vowel performance in isolated words but not in sentences. In addition, the use of vowel cues in sentences was relatively independent of age and auditory sensitivity when audibility is ensured. Combined, results argue that older listeners are able to use essential cues carried by vowels for sentence intelligibility.

A correlational method to concurrently measure envelope and temporal fine structure weights: effects of age, cochlear pathology, and spectral shaping.

The speech signal may be divided into spectral frequency-bands, each band containing temporal properties of the envelope and fine structure. This study measured the perceptual weights for the envelope and fine structure in each of three frequency bands for sentence materials in young normal-hearing listeners, older normal-hearing listeners, aided older hearing-impaired listeners, and spectrally matched young normal-hearing listeners. The availability of each acoustic property was independently varied through noisy signal extraction. Thus, the full speech stimulus was presented with noise used to mask six different auditory channels. Perceptual weights were determined by correlating a listener's performance with the signal-to-noise ratio of each acoustic property on a trial-by-trial basis. Results demonstrate that temporal fine structure perceptual weights remain stable across the four listener groups. However, a different weighting typography was observed across the listener groups for envelope cues. Results suggest that spectral shaping used to preserve the audibility of the speech stimulus may alter the allocation of perceptual resources. The relative perceptual weighting of envelope cues may also change with age. Concurrent testing of sentences repeated once on a previous day demonstrated that weighting strategies for all listener groups can change, suggesting an initial stabilization period or susceptibility to auditory training.

Effect of fundamental-frequency and sentence-onset differences on speech-identification performance of young and older adults in a competing-talker background.

This study investigated the benefits of differences between sentences in fundamental frequency (F0) and temporal onset for sentence pairs among listener groups differing in age and hearing sensitivity. Two experiments were completed with the primary difference between experiments being the way in which the stimuli were presented. Experiment 1 used blocked stimulus presentation, which ultimately provided redundant acoustic cues to mark the target sentence in each pair, whereas Experiment 2 sampled a slightly more restricted stimulus space, but in a completely randomized presentation order. For both experiments, listeners were required to detect a cue word ("Baron") for the target sentence in each pair and to then identify the target words (color, number) that appeared later in the target sentence. Results of Experiment 1 showed that F0 or onset separation cues were beneficial to both cue-word detection and color-number identification performance. There were no significant differences across groups in the ability to detect the cue word, but groups differed in their ability to identify the correct color-number words. Elderly adults with impaired hearing had the greatest difficulty with the identification task despite the application of spectral shaping to restore the audibility of the speech stimuli. For the most part, the primary results of Experiment 1 were replicated in Experiment 2, although, in the latter experiment, all older adults, whether they had normal or impaired hearing, performed worse than young adults with normal hearing. From Experiment 2, the benefits received for a difference in F0 between talkers of 6 semitones were equivalent to those received for an onset asynchrony of 300 ms between sentences and, for such conditions, the combination of both sound-segregation cues resulted in an additive benefit.

Asynchronous vowel-pair identification across the adult life span for monaural and dichotic presentations.

PURPOSE: Temporal order abilities decrease with age. Declining temporal processing abilities may influence the identification of rapid vowel sequences. Identification patterns for asynchronous vowel pairs were explored across the life span. METHOD: Young, middle-aged, and older listeners completed temporal order tasks for pairs of 70-ms and 40-ms vowel stimuli. For a given vowel duration, naturally spoken vowels were equated for duration, intensity, and fundamental frequency. Listeners completed monaural and dichotic temporal order tasks that involved identifying the vowel pair in the correct order. The stimulus onset asynchrony that yielded 50% accuracy for identifying the vowel pair in the correct order was used to equate performance among listeners. Vowel identification response patterns were determined at this stimulus onset asynchrony threshold. RESULTS: Vowel identification patterns were largely consistent across age groups. Older listeners were influenced by the order of certain vowel pairs. Not all vowel pairs were identified equally well. Vowel dominance patterns were also observed, with /a/ being identified most accurately for the vowel pairs tested. Formant dynamics explained, in part, identification and confusion patterns. CONCLUSION: Vowel identification accuracy patterns were reasonably similar across the life span, regardless of presentation mode, vowel duration, or effect of considerable stimulus exposure. Large effects of vowel order were observed, particularly for older listeners.

Factors influencing recognition of interrupted speech.

This study examined the effect of interruption parameters (e.g., interruption rate, on-duration and proportion), linguistic factors, and other general factors, on the recognition of interrupted consonant-vowel-consonant (CVC) words in quiet. Sixty-two young adults with normal-hearing were randomly assigned to one of three test groups, "male65," "female65" and "male85," that differed in talker (male/female) and presentation level (65/85 dB SPL), with about 20 subjects per group. A total of 13 stimulus conditions, representing different interruption patterns within the words (i.e., various combinations of three interruption parameters), in combination with two values (easy and hard) of lexical difficulty were examined (i.e., 13×2=26 test conditions) within each group. Results showed that, overall, the proportion of speech and lexical difficulty had major effects on the integration and recognition of interrupted CVC words, while the other variables had small effects. Interactions between interruption parameters and linguistic factors were observed: to reach the same degree of word-recognition performance, less acoustic information was required for lexically easy words than hard words. Implications of the findings of the current study for models of the temporal integration of speech are discussed.

Auditory temporal-order processing of vowel sequences by young and elderly listeners.

This project focused on the individual differences underlying observed variability in temporal processing among older listeners. Four measures of vowel temporal-order identification were completed by young (N=35; 18-31 years) and older (N=151; 60-88 years) listeners. Experiments used forced-choice, constant-stimuli methods to determine the smallest stimulus onset asynchrony (SOA) between brief (40 or 70 ms) vowels that enabled identification of a stimulus sequence. Four words (pit, pet, pot, and put) spoken by a male talker were processed to serve as vowel stimuli. All listeners identified the vowels in isolation with better than 90% accuracy. Vowel temporal-order tasks included the following: (1) monaural two-item identification, (2) monaural four-item identification, (3) dichotic two-item vowel identification, and (4) dichotic two-item ear identification. Results indicated that older listeners had more variability and performed poorer than young listeners on vowel-identification tasks, although a large overlap in distributions was observed. Both age groups performed similarly on the dichotic ear-identification task. For both groups, the monaural four-item and dichotic two-item tasks were significantly harder than the monaural two-item task. Older listeners' SOA thresholds improved with additional stimulus exposure and shorter dichotic stimulus durations. Individual differences of temporal-order performance among the older listeners demonstrated the influence of cognitive measures, but not audibility or age.

Measures of hearing threshold and temporal processing across the adult lifespan.

Psychophysical data on hearing sensitivity and various measures of supra-threshold auditory temporal processing are presented for large groups of young (18-35 y), middle-aged (40-55 y) and older (60-89 y) adults. Hearing thresholds were measured at 500, 1414 and 4000 Hz. Measures of temporal processing included gap-detection thresholds for bands of noise centered at 1000 and 3500 Hz, stimulus onset asynchronies for monaural and dichotic temporal-order identification for brief vowels, and stimulus onset/offset asynchronies for the monaural temporal masking of vowel identification. For all temporal-processing measures, the impact of high-frequency hearing loss in older adults was minimized by a combination of low-pass filtering the stimuli and use of high presentation levels. The performance of the older adults was worse than that of the young adults on all measures except gap-detection threshold at 1000 Hz. Middle-aged adults performed significantly worse than the young adults on measures of threshold sensitivity and three of the four measures of temporal-order identification, but not for any of the measures of temporal masking. Individual differences are also examined among a group of 124 older adults. Cognition and age were found to be significant predictors, although only 10-27% of the variance could be accounted for by these predictors.

Classification and cue weighting of multidimensional stimuli with speech-like cues for young normal hearing and elderly hearing-impaired listeners.

OBJECTIVE: The purpose of this study was to investigate how young normal-hearing (YNH) and elderly hearing-impaired (EHI) listeners make use of redundant speech-like cues when classifying nonspeech sounds having multiple stimulus dimensions. DESIGN: A total of four experiments were conducted with 10 to 12 listeners per group in each experiment. There were 27 stimuli, making use of all possible combinations of three stimulus values along each of three cue dimensions. Stimuli were comprised of two brief sequential noise bursts separated by a temporal gap. Stimulus dimensions were: (1) the center frequency of the noise bursts; (2) the duration of the temporal gap separating the noise bursts; and (3) the direction of a frequency transition in the second noise burst. RESULTS: Experiment 1 verified that the stimulus values selected resulted in adjacent steps along each stimulus being easily discriminable [(P(c) > or = 90%]). In experiment 2, similarity judgments were obtained for all possible pairs of the 27 stimuli. Multidimensional scaling confirmed that the three acoustic dimensions existed as separate dimensions perceptually. In experiment 3, listeners were then trained to classify three exemplar stimuli. After the training, they were required to classify all 27 stimuli and these results led to the derivation of attentional weights for each stimulus dimension. Both groups focused their attention on the frequency-transition dimension during the classification task. Finally, experiment 4 demonstrated that the attentional weights derived in experiment 3 were reliable and that both EHI and YNH participants could be trained to shift their attention to a cue dimension (temporal-gap) not preferred in experiment 3, although older adults required much more training to achieve this shift in attention. CONCLUSION: For the speech-like, multidimensional acoustic stimuli used here, YNH and EHI listeners attended to the same dimensions of the stimuli when classifying them. In general, the EHI listeners required more time to acquire the ability to categorize the stimuli, and to change their focus to alternate stimulus dimensions.

Contribution of high frequencies to speech recognition in quiet and noise in listeners with varying degrees of high-frequency sensorineural hearing loss.

PURPOSE: The contribution of audible high-frequency information to speech-understanding performance in listeners with varying degrees of high-frequency sensorineural hearing loss was examined. METHOD: Thirty-six elderly hearing-impaired (EHI) and 24 young normal-hearing (YNH) listeners were tested in quiet (+20 dB speech-to-noise ratio [SNR]) and noise (+5 dB SNR) and under different bandpass conditions (narrow, 200-1600 Hz; midband, 200-3200 Hz; broadband, 200-6400 Hz), both without and with spectral shaping of the stimuli. Monosyllabic word-recognition performance was examined through use of both whole-word scoring and phoneme scoring. The 36 EHI listeners were divided into 3 groups of 12 listeners each, with the groups differing in the amount of high-frequency hearing loss. The 24 YNH participants were separated into 2 groups, each serving as a reference group for either the unshaped or spectrally shaped speech listening conditions. RESULTS: Results for spectrally shaped speech, in both quiet and noise, revealed that the 3 EHI groups performed equivalently in the different bandwidth conditions and demonstrated no change (increase or decrease) in word-recognition performance between the midband and broadband conditions. The YNH groups, however, demonstrated improved speech understanding attributable to the higher frequencies for the broadband condition in both the unshaped and shaped conditions. CONCLUSIONS: Data from the EHI listeners revealed that performance for unshaped speech was correlated moderately and negatively with degree of high-frequency hearing loss. Alternatively, recognition performance for shaped speech was related to neither the performance for unshaped speech nor the amount of high-frequency hearing loss.

Auditory speech recognition and visual text recognition in younger and older adults: similarities and differences between modalities and the effects of presentation rate.

PURPOSE: To examine age-related differences in auditory speech recognition and visual text recognition performance for parallel sets of stimulus materials in the auditory and visual modalities. In addition, the effects of variation in rate of presentation of stimuli in each modality were investigated in each age group. METHOD: A mixed-model design was used in which 3 independent groups (13 young adults with normal hearing, 10 elderly adults with normal hearing, and 16 elderly hearing-impaired adults) listened to auditory speech tests (a sentence-in-noise task, time-compressed monosyllables, and a speeded-spelling task) and viewed visual text-based analogs of the auditory tests. All auditory speech materials were presented so that the amplitude of the speech signal was at least 15 dB above threshold through 4000 Hz. RESULTS: Analyses of the group data revealed that when baseline levels of performance were used as covariates in the group analyses the only significant group difference was that both elderly groups performed worse than the young group on the auditory speeded-speech tasks. Analysis of individual data, using correlations, factor analysis, and linear regression, was generally consistent with the group data and revealed significant, moderate correlations of performance for similar tasks across modalities, but stronger correlations across tasks within a modality. This suggests that performance on these tasks was mediated both by a common underlying factor, such as cognitive processing, as well as modality-specific processing. CONCLUSION: Performance on measures of auditory processing of speech examined here was closely associated with performance on parallel measures of the visual processing of text obtained from the same participants. Young and older adults demonstrated comparable abilities in the use of contextual information in each modality, but older adults, regardless of hearing status, had more difficulty with fast presentation of auditory speech stimuli than young adults. There were no differences among the 3 groups with regard to the effects of presentation rate for the visual recognition of text, at least for the rates of presentation used here.

Auditory measures of selective and divided attention in young and older adults using single-talker competition.

In this study, two experiments were conducted on auditory selective and divided attention in which the listening task involved the identification of words in sentences spoken by one talker while a second talker produced a very similar competing sentence. Ten young normal-hearing (YNH) and 13 elderly hearing-impaired (EHI) listeners participated in each experiment. The type of attention cue used was the main difference between experiments. Across both experiments, several consistent trends were observed. First, in eight of the nine divided-attention tasks across both experiments, the EHI subjects performed significantly worse than the YNH subjects. By comparison, significant differences in performance between age groups were only observed on three of the nine selective-attention tasks. Finally, there were consistent individual differences in performance across both experiments. Correlational analyses performed on the data from the 13 older adults suggested that the individual differences in performance were associated with individual differences in memory (digit span). Among the elderly, differences in age or differences in hearing loss did not contribute to the individual differences observed in either experiment.

A comparison of two measures of hearing aid satisfaction in a group of elderly hearing aid wearers.

OBJECTIVE: The objective of this study was to compare the results of two measures of hearing aid satisfaction, an indirect measure (Satisfaction with Amplification in Daily Living, SADL; Cox & Alexander, 1999) and a direct measure (an expanded version of the MarkeTrak-IV survey; Kochkin, 1996), in a group of elderly hearing aid wearers. DESIGN: A total of 43 elderly hearing aid wearers completed both satisfaction measures (order counterbalanced across wearers) after 1 mo of wearing 2-channel wide dynamic range compression (WDRC) in-the-canal (ITC) hearing aids. A correlational research design was employed. RESULTS: The elderly hearing aid wearers in this study yielded results on each measure of hearing aid satisfaction that were generally consistent with those found previously in larger groups of similar samples. The correlation between each measure of satisfaction (r = 0.75) was positive, moderately strong, and significant (p < 0.01) for the global scores of the SADL and MarkeTrak-IV scales. CONCLUSIONS: Although different approaches to the measurement of satisfaction were followed in the development of the SADL (indirect approach) and the MarkeTrak-IV (direct measurement) scales, similar results were obtained with each scale. The 15-item SADL instrument, however, is much shorter than the MarkeTrak-IV instrument and, as a result, is more efficient to administer clinically.