Gary Kidd

Preliminary analyses of interrelations among variables that correlate with measures of speech perception by aided listeners with mild-to-moderately-severe age-related hearing loses are described. The SPATS Group of nearly 120 hearing-aid users was trained in quiet and noise to identify syllable-constituents and to identify words in simple sentences. The Listen Group of about 60 aided listeners listened for an equal amount of time to recorded narratives. All were given audiometric, working memory, intelligence tests, a battery of psycho-acoustic tests, and a battery of speech-perception tests prior to training. The audiometric and speech perception tests were repeated after training and again after a 3-month retention period. Prior to training, there were large individual differences speech perception scores that could only be partially accounted for by the severity of audiometric loss. Training appears to be more effective for the SPATS Group than for the Listen Group. While improvements with training were generally modest, those who were very good or very poor initially tended to show little or no improvement, while those with middling scores tended to show more improvement. Sentence scores are highly correlated with syllable-constituent scores and with the use of context, and the use of context is correlated with working memory. (Miller and Watson are stockholders in communication Disorders Technology, Inc., and may profit from sales of some the software used in this study.)

Successful speech understanding requires the listener to accurately anticipate the temporal onsets of individual words in running speech. The present study investigated listeners’ sensitivity to temporal deviations in sentences with natural or modified speech timing. Subjects listened to sentences in which a portion of speech preceding the final word was replaced by a silent gap. On each trial, an intact sentence was presented, followed by two versions of the sentence with a silent gap: one with the correct timing for the gap (i.e., equal to the duration of the missing speech) and one with altered gap timing (longer or shorter than the missing speech). Listeners judged which version had the altered timing. An adaptive procedure was used to estimate thresholds for the detection of altered timing for early-onset (shortened gap) and late-onset (lengthened gap) final words. In separate conditions, the rhythm of the sentence preceding the gap was either unaltered or rate-modulated according to a sinusoidal modulator. Results showed that the ability to identify the correct gap timing was adversely affected by the manipulation of sentence rhythm, and in both intact and altered rhythmic contexts, listeners were better at detecting early final word onsets than late onsets.

Schizophrenia spectrum disorder (SZ) is associated with deficits in auditory perception as well as auditory verbal hallucinations (AVH). However, the relationship between auditory feature perception and auditory verbal hallucinations (AVH), one of the most commonly occurring symptoms in psychosis, has not been well characterized. This study evaluated perception of a broad range of auditory features in SZ and determined whether current AVHs relate to auditory feature perception. Auditory perception, including frequency, intensity, duration, pulse-train and temporal order discrimination, as well as an embedded tone task, was assessed in both AVH (n = 20) and non-AVH (n = 24) SZ individuals and in healthy controls (n = 29) with the Test of Basic Auditory Capabilities (TBAC). The Hamilton Program for Schizophrenia Voices Questionnaire (HPSVQ) was used to assess the experience of auditory hallucinations in patients with SZ. Findings suggest that compared to controls, the SZ group had greater deficits on an array of auditory features, with non-AVH SZ individuals showing the most severe degree of abnormality. IQ and measures of cognitive processing were positively associated with performance on the TBAC for all SZ individuals, but not with the HPSVQ scores. These findings indicate that persons with SZ demonstrate impaired auditory perception for a broad range of features. It does not appear that impaired auditory perception is associated with recent auditory verbal hallucinations, but instead associated with the degree of intellectual impairment in SZ.

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 Speech Intelligibility Index (SII) assumes additivity of the importance of acoustically independent bands of speech. To further evaluate this assumption, open-set speech recognition was measured for words and sentences, in quiet and in noise, when the speech stimuli were presented to the listener in selected frequency bands. The filter passbands were constructed from various combinations of 20 bands having equivalent (0.05) importance in the SII framework. This permitted the construction of a variety of equal-SII band patterns that were then evaluated by nine different groups of young adults with normal hearing. For monosyllabic words, a similar dependence on band pattern was observed for SII values of 0.4, 0.5, and 0.6 in both quiet and noise conditions. Specifically, band patterns concentrated toward the lower and upper frequency range tended to yield significantly lower scores than those more evenly sampling a broader frequency range. For all stimuli and test conditions, equal SII values did not yield equal performance. Because the spectral distortions of speech evaluated here may not commonly occur in everyday listening conditions, this finding does not necessarily represent a serious deficit for the application of the SII. These findings, however, challenge the band-independence assumption of the theory underlying the SII.

Background: The sooner people receive treatment for hearing loss (HL), the quicker they are able to recognize speech and to master hearing aid technology. Unfortunately, a majority of people with HL wait until their impairments have progressed from moderate to severe levels before seeking auditory rehabilitation. To increase the number of individuals with HL who pursue and receive auditory rehabilitation, it is necessary to improve methods for identifying and informing these people via widely accessible hearing screening procedures. Screening for HL is the first in a chain of events that must take place to increase the number of patients who enter the hearing health-care system. New methods for hearing screening should be readily accessible through a common medium (e.g., telephone or computer) and should be relatively easy and quick for people to self-administer. Purpose: The purpose of this study was to assess a digits-in-noise (DIN) hearing screening test that was delivered via personal computer. Research design: Participants completed the Hearing Handicap Inventory for Adults (HHIA) questionnaire, audiometric testing in a sound booth, and computerized DIN testing. During the DIN test, sequences of three spoken digits were presented in noise via headphones at varying signal-to-noise ratios (SNRs). Participants entered each three-digit sequence they heard using an on-screen keypad. Study sample: Forty adults (16 females, 24 males) participated in the study, of whom 20 had normal hearing and 20 had HL (pure-tone average [PTA] thresholds for 0.5, 1, 2, and 4 kHz >25 dB HL). Data collection and analysis: DIN SNR and PTA data were analyzed and compared for each ear tested. Receiver operating characteristic curves based on these data were plotted. A measure of overall accuracy of a screening test is the area under the receiver operating characteristic curve (AUC). This measures the average true positive rate across false positives at varying DIN SNR cutoffs. Larger values of the AUC indicate, on average, more accurate screening tests. HHIA responses were analyzed and compared to PTA and DIN SNR results using Pearson correlation statistics. Results: HHIA scores were positively correlated with audiometric PTA and DIN SNR results (p < 0.001 for all correlations). For an HL criterion of one or more frequencies from 0.25 to 8 kHz >25 dB HL, the AUC for the DIN test was 0.95. When a criterion of hearling level was set at one or more frequencies from 0.25 to 8 kHz >20 dB HL, the AUC for the DIN test was 0.96. Conclusions: The computer version of the DIN test demonstrated excellent sensitivity and specificity for our sample of 40 participants. AUC results (≥0.95) suggest that this DIN test administered via computer should be very useful for adult hearing screening.

When listening to speech in the presence of competing sounds that render portions of a speech signal inaudible or unrecognizable, the ability to utilize partial speech information is crucial for speech understanding. To better understand this ability, we have been examining word recognition with different patterns of missing information (portions of speech replaced by silence) in words and sentences. Although we find that the major determinant of word recognition is the proportion of missing information, the location of glimpses and the pattern and predictability of glimpses can also influence performance. However, these effects depend on the presence or absence of a sentence context and the predictability of the target word within the sentence. With isolated words, the onset information is most important for recognition. For words in sentences, the importance of word onsets is diminished and depends on the amount of context provided by the sentence. When the pattern of interruptions throughout a sentence is manipulated, a predictable pattern of glimpses facilitates word recognition in a highly predictable sentence context, but not in a low-predictable context. The implications of these findings for theories of speech understanding under difficult listening conditions will be discussed. [Work supported by NIH (NIA and NIDCD).]

Objective: The Dutch digits-in-noise test (NL DIN) and the American-English version (US DIN) are speech-in-noise tests for diagnostic and clinical usage. The present study investigated differences between NL DIN and US DIN speech reception thresholds (SRTs) for a group of native Dutch-speaking listeners. Design: In experiment 1, a repeated-measures design was used to compare SRTs for the NL DIN and US DIN in steady-state noise and interrupted noise for monaural, diotic, and dichotic listening conditions. In experiment 2, a subset of these conditions with additional speech material (i.e. US DIN triplets without inter-digit coarticulation/prosody) was used. Study sample: Experiment 1 was conducted with 16 normal-hearing Dutch students. Experiment 2 was conducted with nine different students. Results: No significant differences between SRTs measured with the NL DIN and US DIN were found in steady-state noise. In interrupted noise the US DIN SRTs were significantly better in monaural and diotic listening conditions. Experiment 2 demonstrated that these better SRTs cannot be explained by the combined effect of inter-digit coarticulation and prosody in the American-English triplets. Conclusions: The NL DIN and US DIN are highly comparable and valuable tests for measuring auditory speech recognition abilities. These tests promote across-language comparisons of results.