Normal-hearing Adult Listeners Research Articles

Acoustic- Versus Intelligibility-Based Assessment of Subjective Listening Difficulty Measured With the Repeat-Recall Test

Objectives: To contrast interpretations of listening effort ratings when judged against acoustic- versus intelligibility-based normative references. Design: Existing data collected from 66 normal-hearing adult listeners, comprising 2730 trials of the Repeat-Recall Test, were used to establish norms of subjective listening effort ratings for six ranges of intelligibility. Data from 21 aided hearing-impaired listeners were then used to contrast intelligibility-based norms against acoustic-based norms when interpreting listening effort ratings measured in omnidirectional and directional microphone conditions. Results: Whereas acoustic-based norms effectively demonstrated reduced effort for directional versus omnidirectional microphone modes, intelligibility-based references controlled for listeners’ performance biases and improved the consistency with which subjective ratings were ranked across the two microphone conditions. Conclusions: The choice of normative reference should be carefully considered when judging listening effort ratings from hearing-impaired individuals against those of their normal-hearing peers. Whereas acoustic-based references may be more useful for evaluating the benefits of hearing aid technology, intelligibility-based references may be better suited to identifying listeners with poor subjective experiences for speech-in-noise related to factors beyond intelligibility.

Intelligibility of Word-Initial Obstruent Consonants in Mandarin-Speaking Prelingually Deafened Children With Cochlear Implants.

This study assessed the intelligibility of obstruent consonants in prelingually deafened Mandarin-speaking children with cochlear implants (CIs). Twenty-two Mandarin-speaking children with normal hearing (NH) aged 3.25-10.0 years and 35 Mandarin-speaking children with CIs aged 3.77-15.0 years were recruited to produce a list of Mandarin words composed of 17 word-initial obstruent consonants in different vowel contexts. The children with CIs were assigned to chronological age-matched (CA) and hearing age-matched (HA) subgroups with reference to the NH controls. One hundred naïve NH adult listeners were recruited for a consonant identification task that consisted of a total of 2,663 stimulus tokens through an online research platform. For each child speaker, the consonant productions were judged by seven to 12 different adult listeners. An average percentage of consonants correct was calculated across all listeners for each consonant. The CI children in both the CA and HA subgroups showed lower intelligibility in their consonant productions than the NH controls. Among the 17 obstruents, both CI subgroups showed higher intelligibility for stops, but they demonstrated major problems with the sibilant fricatives and affricates and showed a different confusion pattern from the NH controls on these sibilants. Of the three places (alveolar, alveolopalatal, and retroflex) in Mandarin sibilants, both CI subgroups showed the lowest intelligibility and the greatest difficulties with alveolar sounds. For the NH children, there was a significant positive relationship between overall consonant intelligibility and chronological age. For the children with CIs, the best fit regression model revealed significant effects of chronological age and age at implantation, with their quadratic terms included. Mandarin-speaking children with CIs experience major challenges in the three-way place contrasts of sibilant sounds in consonant production. Chronological age and the combined effect of CI-related time variables play important roles in the development of obstruent consonants in the CI children.

Comparison of Speech, Spatial, and Qualities of Hearing Scale (SSQ) and the Abbreviated Profile of Hearing Aid Benefit (APHAB) Questionnaires in a Large Cohort of Self-Reported Normal-Hearing Adult Listeners.

The Speech, Spatial, and Qualities of Hearing Scale (SSQ) and the Abbreviated Profile of Hearing Aid Benefit (APHAB) are two most commonly used questionnaires in the audiology clinic to assess an individual's self-perception of their hearing ability. Here, we present the outcomes of these two questionnaires on a large group of self-reported normal hearing adult listeners. A total of 254 self-reported normal-hearing younger and older adults completed the SSQ and the APHAB questionnaire. The younger participants completed the questionnaires through Qualtrics, whereas the older participants completed the questionnaire through Qualtrics and a traditional pen-and-paper method. The younger listeners perceived a higher ability compared to the older adults in all the SSQ subscales (Speech, Spatial, and Qualities) and reported a lesser frequency of the problems in three of the four APHAB subscales (Ease of communication, Reverberation, and Background Noise). There was no significant difference in the frequency of the problems reported in the Aversiveness subscale. Self-reported normal-hearing listeners do not rate their listening ability at the top of the ability scale. Additionally, the large dataset presented here has a potential normative value for the SSQ and the APHAB questionnaires for self-reported normal-hearing adult listeners.

Objective Detection of the Speech Frequency Following Response (sFFR): A Comparison of Two Methods.

Speech frequency following responses (sFFRs) are increasingly used in translational auditory research. Statistically-based automated sFFR detection could aid response identification and provide a basis for stopping rules when recording responses in clinical and/or research applications. In this brief report, sFFRs were measured from 18 normal hearing adult listeners in quiet and speech-shaped noise. Two statistically-based automated response detection methods, the F-test and Hotelling’s T2 (HT2) test, were compared based on detection accuracy and test time. Similar detection accuracy across statistical tests and conditions was observed, although the HT2 test time was less variable. These findings suggest that automated sFFR detection is robust for responses recorded in quiet and speech-shaped noise using either the F-test or HT2 test. Future studies evaluating test performance with different stimuli and maskers are warranted to determine if the interchangeability of test performance extends to these conditions.

Amplitude modulation of background noise varies listeners’ spectral weights for sentence recognition

The band importance function that captures how the spectral weight varies across frequencies was estimated for sentence recognition in noises with steady-state or fluctuating temporal envelopes from ten young, normal-hearing adult listeners. The test sentences were from either the IEEE or AzBio corpus. The background noise was a 12-talker babble, either unmodulated or amplitude-modulated using an 8-Hz sinusoidal modulator. In the co-located condition, the noise was presented from the same loudspeaker as the target sentence in front of the listener (0°). In the spatially separated condition, the noise was presented simultaneously from two loudspeakers on either side of the target speaker (±90°). The co-located condition was replicated in a separated test session, at least one week from the first session, which demonstrated the reliability of the estimated band importance functions. With the introduction of amplitude modulation, an increase of spectral weight in the 2-kHz frequency band and a decrease of weight in the 250-Hz band was observed, which was consistent for the two test materials and for the two spatial placements of the noise. Compared to amplitude modulation, spatial separation between the target and noise had a less influence on the band importance function.

Enhancement of the Auditory Late Response (N1-P2) by Presentation of Stimuli From an Unexpected Location.

Passive electrophysiological protocols, such as the middle latency response and speech auditory brainstem response, are often advocated in the objective assessment of central auditory processing disorder (CAPD). However, few established electrophysiological protocols exist for CAPD assessment that have patients participate in active tasks which more closely approximate real-world listening. To this end, the present study used a discrimination task (i.e., oddball paradigm) to measure an enhancement of the auditory late response (N1-P2) that occurs when participants direct their auditory attention toward speech arising from an unexpected spatial location. To establish whether N1-P2 is enhanced when auditory attention is directed toward an unexpected location during a two-word discrimination task. In addition, it was also investigated whether any enhancements in this response were contingent on the stimulus being counted as part of the oddball paradigm. Prospective study with a repeated measures design. Ten normal hearing adults, with an age range of 18-24 years. The N1 and P2 latencies and peak-to-peak amplitudes were recorded during a P300 paradigm. A series of repeated measures of analysis of variance and a correlation analysis was performed. There was a significant effect of stimulus location, in which words arising from the unexpected location showed a larger N1-P2 peak-to-peak amplitude and an earlier N1 latency. This effect was seen regardless of whether or not participants had to count the word total in memory. These findings suggest that spatial enhancement of the N1-P2 is a fairly robust phenomenon in normal hearing adult listeners. Additional studies are needed to determine whether this enhancement is absent or reduced in patients with CAPD.

Effects of nonlinear frequency compression on the acoustic properties and recognition of speech sounds in Mandarin Chinese.

The present study examined the change in spectral properties of Mandarin vowels and fricatives caused by nonlinear frequency compression (NLFC) used in hearing instruments and how these changes affect the perception of speech sounds in normal-hearing listeners. Speech materials, including a list of Mandarin monosyllables in the form of /dV/ (12 vowels) and /Ca/ (five fricatives), were recorded from 20 normal-hearing, native Mandarin-speaking adults (ten males and ten females). NLFC was based on Phonak SoundRecover algorithms. The speech materials were processed with six different NLFC parameter settings. Detailed acoustic analysis revealed that the high front vowel /i/ and certain compound vowels containing /i/ demonstrated positional deviation in certain processed conditions in comparison to the unprocessed condition. All five fricatives showed acoustic changes in spectral features in all processed conditions. Fourteen Mandarin-speaking, normal-hearing adult listeners performed phoneme recognition with the six NLFC processing conditions. When the cut-off frequency was set relatively low, recognition of /s/ was detrimentally affected, whereas none of the NLFC processing configurations affected the other phonemes. The discrepancy between the considerable acoustic changes and the negligible adverse effects on perceptual outcomes is partially accounted for by the phonology system and phonotactic constraints in Mandarin.

Turn an Ear to Hear: How Hearing-Impaired Listeners Can Exploit Head Orientation to Enhance Their Speech Intelligibility in Noisy Social Settings.

Turning an ear toward the talker can enhance spatial release from masking. Here, with their head free, listeners attended to speech at a gradually diminishing signal-to-noise ratio and with the noise source azimuthally separated from the speech source by 180° or 90°. Young normal-hearing adult listeners spontaneously turned an ear toward the speech source in 64% of audio-only trials, but a visible talker’s face or cochlear implant (CI) use significantly reduced this head-turn behavior. All listener groups made more head movements once instructed to explore the potential benefit of head turns and followed the speech to lower signal-to-noise ratios. Unilateral CI users improved the most. In a virtual restaurant simulation with nine interfering noises or voices, hearing-impaired listeners and simulated bilateral CI users typically obtained a 1 to 3 dB head-orientation benefit from a 30° head turn away from the talker. In diffuse interference environments, the advice to U.K. CI users from many CI professionals and the communication guidance available on the Internet most often advise the CI user to face the talker head on. However, CI users would benefit from guidelines that recommend they look sidelong at the talker with their better hearing or implanted ear oriented toward the talker.

Perceived anger in clear and conversational speech: Effect of aging and hearing loss

Previous research suggests that young normal-hearing and older hearing-impaired adult listeners judge clear speech as sounding angry more often than conversational speech. Interestingly, older hearing-impaired listeners were less likely than young normal-hearing listeners to judge sentences as angry in both speaking styles. It was unknown, however, whether this difference in ratings of emotion were driven by the age or hearing status differences between the two groups. A secondary investigation showed that young adult listeners with a simulated hearing loss that matched the older hearing-impaired group rated emotions nearly identically to the young normal-hearing group, suggesting no effect of hearing loss on ratings of emotion. The simulated hearing loss failed to account for other auditory factors or psychological processes associated with aging that may have account for the group differences. The present study carried out the same emotional rating task using clear and conversational speech sentences (a...

Investigating the role of supra-threshold auditory processing and cognitive abilities in presbyacusis

Anecdotal evidence and experimental investigations indicate that older people experience increased speech-perception difficulties, especially in noisy environments. Since peripheral hearing sensitivity declines with age, lower speech intelligibility can often be explained by a reduction in audibility. However, aided speech-perception in hearing-impaired listeners frequently falls short of the performance level that would be expected based on the audibility of the speech signal. Given that many of these listeners are older, poor performance may be partly caused by age-related changes in supra-threshold auditory and/or cognitive processes that are not captured by an audiometric assessment. The presentation will discuss experimental evidence obtained from clinically normal-hearing adult listeners showing that auditory temporal processing, cognition, and speech-in-noise perception are indeed linked and, independently of hearing loss, decline across the adult lifespan. These findings highlight the need to take...

Spatial release from masking in children with bilateral cochlear implants and with normal hearing: Effect of target-interferer similarity.

In complex auditory environments, it is often difficult to separate a target talker from interfering speech. For normal hearing (NH) adult listeners, similarity between the target and interfering speech leads to increased difficulty in separating them; that is, informational masking occurs due to confusability of the target and interferers. This study investigated performance of children with bilateral cochlear implants (BiCIs) when target and interferers were either same-sex (male) talkers, or different-sex talkers (male target, female interferer). Comparisons between children with BiCIs and NH, when matched for age, were also conducted. Speech intelligibility was measured for target and interferers spatially co-located, or spatially separated with the interferers positioned symmetrically (+90° and -90°) or asymmetrically (both at +90°, right). Spatial release from masking (SRM) was computed as the difference between co-located and separated conditions. Within group BiCI comparisons revealed that in the co-located condition speech intelligibility was worse with the same-sex vs different-sex stimuli. There was also a trend for more SRM with the same-sex vs different-sex stimuli. When comparing BiCI to NH listeners, SRM was larger for the NH groups, suggesting that NH children are better able to make use of spatial cues to improve speech understanding in noise.

Melodic Contour Training and Its Effect on Speech in Noise, Consonant Discrimination, and Prosody Perception for Cochlear Implant Recipients.

Cochlear implant (CI) recipients generally have good perception of speech in quiet environments but difficulty perceiving speech in noisy conditions, reduced sensitivity to speech prosody, and difficulty appreciating music. Auditory training has been proposed as a method of improving speech perception for CI recipients, and recent efforts have focussed on the potential benefits of music-based training. This study evaluated two melodic contour training programs and their relative efficacy as measured on a number of speech perception tasks. These melodic contours were simple 5-note sequences formed into 9 contour patterns, such as “rising” or “rising-falling.” One training program controlled difficulty by manipulating interval sizes, the other by note durations. Sixteen adult CI recipients (aged 26–86 years) and twelve normal hearing (NH) adult listeners (aged 21–42 years) were tested on a speech perception battery at baseline and then after 6 weeks of melodic contour training. Results indicated that there were some benefits for speech perception tasks for CI recipients after melodic contour training. Specifically, consonant perception in quiet and question/statement prosody was improved. In comparison, NH listeners performed at ceiling for these tasks. There was no significant difference between the posttraining results for either training program, suggesting that both conferred benefits for training CI recipients to better perceive speech.

Neural Coding of Phonemic Fricative Contrast With and Without Hearing Aid

To determine whether auditory event-related potentials (ERPs) to a phonemic fricative contrast ("s" and "sh") show significant differences in listening conditions with or without a hearing aid and whether the aided condition significantly alters a listener's ERP responses to the fricative speech sounds. The raw EEG data were collected using a 64-channel system from 10 healthy adult subjects with normal hearing. The fricative stimuli were digitally edited versions of naturally produced syllables, /sa/ and /∫a/. The evoked responses were derived in unaided and aided conditions by using an alternating block design with a passive listening task. Peak latencies and amplitudes of the P1-N1-P2 components and the N1' and P2'' peaks of the acoustic change complex (ACC) were analyzed. The evoked N1 and N1' responses to the fricative sounds significantly differed in the unaided condition. The fricative contrast also elicited distinct N1-P2 responses in the aided condition. While the aided condition increased and delayed the N1 and ACC responses, significant differences in the P1-N1-P2 and ACC components were still observed, which would support fricative contrast perception at the cortical level. Despite significant alterations in the ERP responses by the aided condition, normal-hearing adult listeners showed distinct neural coding patterns for the voiceless fricative contrast, "s" and "sh," with or without a hearing aid.

Melody Recognition in Dichotic Listening With or Without Frequency-Place Mismatch

The purpose of the study was to examine recognition of degraded melodic stimuli in dichotic listening with or without frequency-place mismatch. Melodic stimuli were noise vocoded with various number-of-channel conditions in a dichotic and monaural processor. In the dichotic zipper processor, the odd-indexed channels were tonotopically matched and presented to the left ear while the even-indexed channels were tonotopically matched or upward shifted in frequency and presented to the right ear. In the monaural processor, all channels either unshifted or shifted were presented to the left ear alone. Familiar melody recognition was measured in 16 normal-hearing adult listeners. Performance for dichotically presented melodic stimuli did not differ from that for monaurally presented stimuli even with low spectral resolution (8 channels). With spectral shift introduced in one ear, melody recognition decreased with increasing spectral shift in a nonmonotonic fashion. With spectral shift, melody recognition in dichotic listening was either not different or superior in a few cases relative to the monaural condition. With no spectral shift, cohesive fusion of dichotically presented melodic stimuli did not seem to depend on spectral resolution. In spectrally shifted conditions, listeners may have suppressed the partially shifted channels in the right ear and selectively attended only to the unshifted ones, resulting in dichotic advantages for melody recognition in some cases.

Speech understanding in adults and children for sentences with cochlear-implant simulated spectral degradation and shallow insertion depth

While previous studies have compared cochlear-implant simulated (i.e., vocoded) speech understanding between adults and children, they have been acute experiments that have not considered long-term adaptation or training effects. Normal-hearing adult listeners demonstrate significant improvement in vocoded speech understanding with training, particularly if there is simulated frequency-to-place mismatch. The purpose of this study was to compare how adults and children adapt to eight-channel sine-vocoded speech with 0, 3, and 6 mm of frequency-to-place mismatch. Twenty adults (>18 yrs) and ten children (8–10 yrs) were trained on vocoded speech understanding over a four-hour period. The stimuli were a closed set of 40 simple words from which five-word nonsense sentences were constructed. Speech understanding was measured in 45-trial blocks where no feedback was provided, followed by 30-trial blocks where visual and auditory feedback was provided. High variability existed within both groups. On average, children performed worse than adults. Over the first five testing/training blocks, children improved at a slower rate than adults. Some children showed minimal improvement over the testing, whereas most of the adults showed noticeable improvement. These results suggest that adults have developed neural mechanisms that can more effectively adapt to and process degraded and frequency-shifted speech.

Influence of cochlear implantation on sentence intelligibility and duration

Cochlear implants (CI) allow children with hearing loss (HL) to achieve speech perception and production outcomes that make their spoken speech understandable to normal hearing adult listeners. This capability is characterize by wide variability of scores. In order to understand the factors that contribute to the overall variability, we investigated the effects of duration of cochlear implantation on speech intelligibility and sentence duration over time. Participants were 105 children implanted between the ages of 2 and 4 and tested at 2 time points there they were 8 and 16 years old. Participants repeated McGarr sentences, which vary in length from 3 to 5 to 7 syllables. Recording were analyze using acoustic software to designate the beginning and end of each sentence in listeners who only heard one sentence from one child. Speech intelligibility scores were related statistically to the duration of each sentence. Durations of sentences that approximated that of normal hearing listeners were those with high intelligibility judgment. In addition, it appears that the children with the longest experience of CI use continue to improve their intelligibility. [Sponsored by NIH.]

The Effects of Auditory Short-Term Training in Passive Oddball Paradigm with Novel Stimuli

Background and ObjectivesThe purpose of this study was to determine how human neural activity might be changed through auditory short-term training when listening to novel stimuli.Subjects and MethodsAmong the twenty young normal hearing adult listeners who participated, ten were randomly assigned to a training group and ten were assigned to a non-training group as a control. Two synthesized novel stimuli were used: /su/ and /∫u/. Both stimuli similarly sounded like /su/, but had two different onset transition frequencies and fricative pole frequencies. In the experiment, behavioral identification test (i.e., /su/ vs. /∫u/) and the mismatch negativity (MMN) were measured before and after training for the training group. To gauge the training effect, the listeners in the training group were taught by discrimination and identification of two novel stimuli for about 20 minutes.ResultsThe results showed that scores for the behavioral test increased significantly after auditory short-term training. Also, onset latency, duration, and area of the MMN were significantly changed when elicited by the training stimuli.ConclusionsThese findings indicated that auditory short-term training could change human neural activity, suggesting future clinical applications for auditory training.

Gender Identification in Younger and Older Adults

The aim of this study was to investigate potential effects of age on the ability of normal-hearing (NH) adult listeners to utilize spectral and temporal cues when performing a voice gender identification task. Ten younger and 10 older NH adult listeners were measured on their ability to correctly identify the speaker gender of six different vowel tokens (H-/vowel/-D) when spoken by eight speakers (four male and four female). Spectral (number of channels) and temporal cues (low-pass cut-off frequency for temporal envelope extraction) were systematically manipulated using noiseband vocoding techniques; stimuli contained 1, 4, 8, 16, or 32 spectral channels, while the low-pass cut-off frequency of the temporal envelope filter was 20, 50, 100, 200, or 400 Hz. Furthermore, the fundamental frequencies (F0s) of the vowel tokens were manipulated to create two conditions: "Expanded" (large range of F0 values) and "Compressed" (small range of F0 values). In general, younger listeners performed better than the older listeners but only when stimuli were spectrally degraded. For both the Expanded and Compressed conditions, the overall performance of the younger listeners was better than that of the older listeners, suggesting age-related deficits in both spectral and temporal processing. Furthermore, a significant interaction between age group and temporal envelope cues revealed that older listeners received less benefit from increasing temporal envelope information compared with the benefit observed among younger listeners. In particular, the performance of the younger NH group (collapsed across number of channels), but not the older NH group, improved as the temporal envelope cut-off frequency was increased from 50 to 400 Hz. The results reported here support previous findings of senescent declines in perceiving spectrally reduced speech and temporal amplitude modulation processing. These results suggest that when F0 values are similar to one another, younger listeners can use temporal cues alone to glean voice-pitch information but older listeners exhibit a lessened ability to use such cues. Previous studies have demonstrated the importance of temporal envelope cues in periodicity perception (e.g., gender recognition) by cochlear implant listeners. The results of this study suggest that aging affects the use of such cues, and consequently gender recognition might be poorer among older cochlear implant recipients.

Auditory Mismatch Negativity: Detecting Spectral Contrasts in a Modulated Noise

The ability to detect sinusoidal spectral envelope from an unmodulated (flat) spectrum has shown a strong correlation with speech perception in quiet and noisy listening conditions in normal hearing, hearing-impaired, and cochlear implant users. In this study, the mismatch negativity (MMN) was collected from 10 normal-hearing adult listeners and used to determine if modulation detection thresholds derived electrophysiologically correlate with the psychophysically measured spectral modulation detection thresholds. MMNs were present for most participants with spectral contrasts of 10 and 20 dB, suggesting that the MMN may be a promising neurophysiologic measure of spectral envelope perception when nonbehavioral measures are desired.

Dichotic Speech Recognition Using CVC Word and Nonsense CVC Syllable Stimuli

The effects of stimulus material, lexical content, and response condition on dichotic speech recognition performance characteristics were examined for normal-hearing young adult listeners. No previous investigation has systematically examined the effects of stimulus material with constant phonetic content but varied lexical content across three response conditions typically used to evaluate binaural auditory processing abilities. To examine how dichotic speech recognition performance varies for stimulus materials with constant phonetic content but varied lexical content across the free recall, directed recall right, and directed recall left response conditions. Dichotic speech recognition was evaluated using consonant-vowel-consonant (CVC) word and nonsense CVC syllable stimuli administered in the free recall, directed right, and directed left response conditions, a repeated measures experimental design. Thirty normal-hearing young adults (15 male, 15 female) served as participants. Participants ranged in age from 18 to 31 yr and were all right-handed. Participants engaged in monaural speech recognition and dichotic speech recognition tasks. Percent correct recognition per ear, as well as ear advantage for dichotic speech recognition, were calculated and evaluated using a repeated measures analysis of variance (ANOVA) statistical procedure. Dichotic speech recognition performance for nonsense CVC syllables was significantly poorer than performance for CVC words, suggesting that lexical content impacts performance on dichotic speech recognition tasks. Performance also varied across response condition, which is consistent with previous studies of dichotic speech recognition. Lexical content of stimulus materials impacts performance characteristics for dichotic speech recognition tasks in the normal-hearing young adult population. The use of nonsense CVC syllable material may provide a way to assess dichotic speech recognition performance while potentially lessening the effects of lexical content on performance.