Amplification Self-Adjustment: Controls and Repeatability.

OBJECTIVES: This study was a continuation of work on an explore-and-select approach to the self-adjustment of amplification. Goals were to determine (i) the effect of changing the number of adjustment controls from three to two, (ii) the effect of changing the initial adjustment from overall output to high-frequency output, (iii) individual repeatability, (iv) the effect on phoneme recognition of increasing and decreasing overall output relative to the starting and adjusted conditions, and (v) listener reactions to, and opinions of, the self-adjustment procedure. DESIGN: Twenty-two adults with hearing loss, 10 of whom were hearing aid users, adjusted level and spectrum of connected speech to preference, using three configurations of number and order of adjustment parameters. The three adjustments were replicated to give a total of six. Presentation was monaural, in quiet, using the ear with the better threshold at 2 kHz. The starting condition was a generic prescription for a typical mild-to-moderate hearing loss. Real ear output spectra were measured for the 6 self-adjustments, the generic starting condition, and the individual NAL-NL2 prescriptions for speech at 65 dB SPL. Monaural phoneme recognition in monosyllables was assessed, in quiet, at levels of -14, -7, 0 and +7 dB relative to both the starting and the self-adjusted conditions. Participants completed a questionnaire and their comments on each question were transcribed. RESULTS: Changing the number of listener controls from 3 to 2 reduced mean adjustment time by around 50% but had negligible effect on group-mean output response. Starting adjustment with high-frequency output rather than overall output resulted in a 2 to 3 dB reduction of group-mean self-adjusted output below 1 kHz. Individual self-adjustments were within ±5 dB of NAL-NL2 prescription (for a 65 dB SPL speech input) for two-thirds of the participants in the high frequencies and for just over half in the low frequencies. In six self-adjustments, individuals self-adjusted, on average, to within ±4 dB of their own mean in both high and low frequencies. There was no evidence that these findings differed for hearing aid users and nonusers. Changes of overall output by ±7 dB after self-adjustment did not significantly affect group mean phoneme recognition. Preference for number and order of self-adjustment differed among participants, as did opinions on self-fitting of hearing aids. CONCLUSIONS: These findings support the conclusion that, for many adults with hearing loss, an explore-and-select procedure for self-adjustment of amplification leads to output values that are repeatable within a few dB, are relatively immune to the number and order of adjustment parameters, and place the average listener well along the plateau of a phoneme recognition versus amplitude function.

Subjective criteria underlying noise-tolerance in the presence of speech.

OBJECTIVE: The objective was to determine the relative contribution of four criteria (loudness, annoyance, distraction, speech interference) to participants' noise-tolerance thresholds (NTT). DESIGN: While listening to speech in noise set at the highest signal-to-noise ratio at which noise became unacceptable (noise tolerance threshold), participants completed paired-comparison judgments of loudness, annoyance, distraction, and speech interference to determine the noise domain(s) that were most important in their noise tolerance judgments. Participants also completed absolute ratings of the noise using the same noise domains, which were combined with the paired comparison data for analysis. STUDY SAMPLE: Sixty-three adults with normal hearing participated. RESULTS: For the entire group, speech interference and distraction were the largest contributors to noise tolerance. A cluster analysis indicated three distinct groups: criteria were dominated by either annoyance (33%); distraction (48%), or speech interference (19%). Significant differences in NTT among the groups revealed the highest mean NTT for the annoyance group and lowest NTT for the speech interference group. CONCLUSION: The majority of participants based NTTs on criteria related to the noise itself (annoyance or distraction) and had greater noise sensitivity than the smaller group of participants who focused more on speech intelligibility in the noise.

Autonomic Nervous System Reactivity During Speech Repetition Tasks: Heart Rate Variability and Skin Conductance.

Cognitive and emotional challenges may elicit a physiological stress response that can include arousal of the sympathetic nervous system (fight or flight response) and withdrawal of the parasympathetic nervous system (responsible for recovery and rest). This article reviews studies that have used measures of electrodermal activity (skin conductance) and heart rate variability (HRV) to index sympathetic and parasympathetic activity during auditory tasks. In addition, the authors present results from a new study with normal-hearing listeners examining the effects of speaking rate on changes in skin conductance and high-frequency HRV (HF-HRV). Sentence repetition accuracy for normal and fast speaking rates was measured in noise using signal to noise ratios that were adjusted to approximate 80% accuracy (+3 dB fast rate; 0 dB normal rate) while monitoring skin conductance and HF-HRV activity. A significant increase in skin conductance level (reflecting sympathetic nervous system arousal) and a decrease in HF-HRV (reflecting parasympathetic nervous system withdrawal) were observed with an increase in speaking rate indicating sensitivity of both measures to increased task demand. Changes in psychophysiological reactivity with increased auditory task demand may reflect differences in listening effort, but other person-related factors such as motivation and stress may also play a role. Further research is needed to understand how psychophysiological activity during listening tasks is influenced by the acoustic characteristics of stimuli, task demands, and by the characteristics and emotional responses of the individual.

Hearing Impairment and Cognitive Energy: The Framework for Understanding Effortful Listening (FUEL).

The Fifth Eriksholm Workshop on "Hearing Impairment and Cognitive Energy" was convened to develop a consensus among interdisciplinary experts about what is known on the topic, gaps in knowledge, the use of terminology, priorities for future research, and implications for practice. The general term cognitive energy was chosen to facilitate the broadest possible discussion of the topic. It goes back to who described the effects of attention on perception; he used the term psychic energy for the notion that limited mental resources can be flexibly allocated among perceptual and mental activities. The workshop focused on three main areas: (1) theories, models, concepts, definitions, and frameworks; (2) methods and measures; and (3) knowledge translation. We defined effort as the deliberate allocation of mental resources to overcome obstacles in goal pursuit when carrying out a task, with listening effort applying more specifically when tasks involve listening. We adapted Kahneman's seminal (1973) Capacity Model of Attention to listening and proposed a heuristically useful Framework for Understanding Effortful Listening (FUEL). Our FUEL incorporates the well-known relationship between cognitive demand and the supply of cognitive capacity that is the foundation of cognitive theories of attention. Our FUEL also incorporates a motivation dimension based on complementary theories of motivational intensity, adaptive gain control, and optimal performance, fatigue, and pleasure. Using a three-dimensional illustration, we highlight how listening effort depends not only on hearing difficulties and task demands but also on the listener's motivation to expend mental effort in the challenging situations of everyday life.

Effects of hearing loss on heart rate variability and skin conductance measured during sentence recognition in noise.

OBJECTIVE: The purpose of the study was to determine the effects of hearing loss and noise on (1) two autonomic nervous system measures associated with stress (skin conductance and heart rate variability) and on (2) subjective ratings of workload/stress. The authors hypothesized that hearing loss would increase psychophysiological and subjective reactivity to noise during speech recognition tasks. Both psychophysiological and subjective indicators of workload/stress were expected to increase with a reduction in signal-to-noise ratio. DESIGN: Sentence recognition in the presence of babble noise was assessed in 15 adults with clinically normal hearing and 18 adults with sensorineural hearing loss. Mean sentence recognition was equalized for the two groups using an adaptive procedure to estimate 80% recognition of words in sentences. Sentences were then presented in quiet and at four fixed signal-to-noise ratios: -6, -3, 0, and +3 dB relative to the individually determined signal-to-noise thresholds. Electrocardiography and skin conductance recordings were obtained during each listening condition. The high-frequency spectral component of heart rate variability was extracted from the electrocardiographic recordings as a measure of parasympathetic nervous system activity. Subjective ratings of effort, mental demand, stress, and perceived performance were obtained after each listening condition using the National Aeronautics and Space Administration Task Load Index. RESULTS: Recognition scores referenced to the adaptive threshold were similar for the two groups. Participants with hearing loss showed a decrease in high-frequency heart rate variability at lower signal-to-noise ratios, whereas those with normal hearing did not. Skin conductance levels were not sensitive to changes in signal-to-noise ratio. However, overall skin conductance reactivity to noise (relative to quiet) was higher for those with hearing loss than for those with normal hearing. In contrast to the psychophysiological findings, there were no significant differences between subjective ratings for the two groups. CONCLUSIONS: Listeners with hearing loss show greater autonomic nervous system reactivity to babble noise during speech recognition than do listeners with normal hearing, when recognition performance is equal. The findings are consistent with the conclusion that listeners with hearing loss experience increased effort and/or stress during speech recognition in noise.

Effects of fundamental frequency and vocal-tract length cues on sentence segregation by listeners with hearing loss.

The purpose was to determine the effect of hearing loss on the ability to separate competing talkers using talker differences in fundamental frequency (F0) and apparent vocal-tract length (VTL). Performance of 13 adults with hearing loss and 6 adults with normal hearing was measured using the Coordinate Response Measure. For listeners with hearing loss, the speech was amplified and filtered according to the NAL-RP hearing aid prescription. Target-to-competition ratios varied from 0 to 9 dB. The target sentence was randomly assigned to the higher or lower values of F0 or VTL on each trial. Performance improved for F0 differences up to 9 and 6 semitones for people with normal hearing and hearing loss, respectively, but only when the target talker had the higher F0. Recognition for the lower F0 target improved when trial-to-trial uncertainty was removed (9-semitone condition). Scores improved with increasing differences in VTL for the normal-hearing group. On average, hearing-impaired listeners did not benefit from VTL cues, but substantial inter-subject variability was observed. The amount of benefit from VTL cues was related to the average hearing loss in the 1-3-kHz region when the target talker had the shorter VTL.

Subjective and psychophysiological indexes of listening effort in a competing-talker task.

BACKGROUND: The effects of noise and other competing backgrounds on speech recognition performance are well documented. There is less information, however, on listening effort and stress experienced by listeners during a speech-recognition task that requires inhibition of competing sounds. PURPOSE: The purpose was (a) to determine if psychophysiological indexes of listening effort were more sensitive than performance measures (percentage correct) obtained near ceiling level during a competing speech task, (b) to determine the relative sensitivity of four psychophysiological measures to changes in task demand, and (c) to determine the relationships between changes in psychophysiological measures and changes in subjective ratings of stress and workload. RESEARCH DESIGN: A repeated-measures experimental design was used to examine changes in performance, psychophysiological measures, and subjective ratings in response to increasing task demand. STUDY SAMPLE: Fifteen adults with normal hearing participated in the study. The mean age of the participants was 27 (range: 24-54). DATA COLLECTION AND ANALYSIS: Psychophysiological recordings of heart rate, skin conductance, skin temperature, and electromyographic (EMG) activity were obtained during listening tasks of varying demand. Materials from the Dichotic Digits Test were used to modulate task demand. The three levels of task demand were single digits presented to one ear (low-demand reference condition), single digits presented simultaneously to both ears (medium demand), and a series of two digits presented simultaneously to both ears (high demand). Participants were asked to repeat all the digits they heard, while psychophysiological activity was recorded simultaneously. Subjective ratings of task load were obtained after each condition using the National Aeronautics and Space Administration Task Load Index questionnaire. Repeated-measures analyses of variance were completed for each measure using task demand and session as factors. RESULTS: Mean performance was higher than 96% for all listening tasks. There was no significant change in performance across listening conditions for any listener. There was, however, a significant increase in mean skin conductance and EMG activity as task demand increased. Heart rate and skin temperature did not change significantly. There was no strong association between subjective and psychophysiological measures, but all participants with mean normalized effort ratings of greater than 4.5 (i.e., effort increased by a factor of at least 4.5) showed significant changes in skin conductance. CONCLUSIONS: Even in the absence of substantial performance changes, listeners may experience changes in subjective and psychophysiological responses consistent with the activation of a stress response. Skin conductance appears to be the most promising measure for evaluating individual changes in psychophysiological responses during listening tasks.

Hearing Aid Self-Adjustment: Effects of Formal Speech-Perception Test and Noise.

While listening to recorded sentences with a sound-field level of 65 dB SPL, 24 adults with hearing-aid experience used the "Goldilocks" explore-and-select procedure to adjust level and spectrum of amplified speech to preference. All participants started adjustment from the same generic response. Amplification was provided by a custom-built Master Hearing Aid with online processing of microphone input. Primary goals were to assess the effects of including a formal speech-perception test between repeated self-adjustments and of adding multitalker babble (signal-to-noise ratio +6 dB) during self-adjustment. The speech test did not affect group-mean self-adjusted output, which was close to the National Acoustics Laboratories' prescription for Non-Linear hearing aids. Individuals, however, showed a wide range of deviations from this prescription. Extreme deviations at the first self-adjustment fell by a small but significant amount at the second. The multitalker babble had negligible effect on group-mean self-selected output but did have predictable effects on word recognition in sentences and on participants' opinion regarding the most important subjective criterion guiding self-adjustment. Phoneme recognition in monosyllabic words was better with the generic starting response than without amplification and improved further after self-adjustment. The findings continue to support the efficacy of hearing aid self-fitting, at least for level and spectrum. They do not support the need for inclusion of a formal speech-perception test, but they do support the value of completing more than one self-adjustment. Group-mean data did not indicate a need for threshold-based prescription as a starting point for self-adjustment.

A comparison of presentation levels to maximize word recognition scores.

BACKGROUND: While testing suprathreshold word recognition at multiple levels is considered best practice, studies on practice patterns do not suggest that this is common practice. Audiologists often test at a presentation level intended to maximize recognition scores, but methods for selecting this level are not well established for a wide range of hearing losses. PURPOSE: To determine the presentation level methods that resulted in maximum suprathreshold phoneme-recognition scores while avoiding loudness discomfort. RESEARCH DESIGN: Performance-intensity functions were obtained for 40 participants with sensorineural hearing loss using the Computer-Assisted Speech Perception Assessment. Participants had either gradually sloping (mild, moderate, moderately severe/severe) or steeply sloping losses. Performance-intensity functions were obtained at presentation levels ranging from 10 dB above the SRT to 5 dB below the UCL (uncomfortable level). In addition, categorical loudness ratings were obtained across a range of intensities using speech stimuli. Scores obtained at UCL - 5 dB (maximum level below loudness discomfort) were compared to four alternative presentation-level methods. The alternative presentation-level methods included sensation level (SL; 2 kHz reference, SRT reference), a fixed-level (95 dB SPL) method, and the most comfortable loudness level (MCL). For the SL methods, scores used in the analysis were selected separately for the SRT and 2 kHz references based on several criteria. The general goal was to choose levels that represented asymptotic performance while avoiding loudness discomfort. The selection of SLs varied across the range of hearing losses. RESULTS: Scores obtained using the different presentation-level methods were compared to scores obtained using UCL - 5 dB. For the mild hearing loss group, the mean phoneme scores were similar for all presentation levels. For the moderately severe/severe group, the highest mean score was obtained using UCL - 5 dB. For the moderate and steeply sloping groups, the mean scores obtained using 2 kHz SL were equivalent to UCL - 5 dB, whereas scores obtained using the SRT SL were significantly lower than those obtained using UCL - 5 dB. The mean scores corresponding to MCL and 95 dB SPL were significantly lower than scores for UCL - 5 dB for the moderate and the moderately severe/severe group. CONCLUSIONS: For participants with mild to moderate gradually sloping losses and for those with steeply sloping losses, the UCL - 5 dB and the 2 kHz SL methods resulted in the highest scores without exceeding listeners' UCLs. For participants with moderately severe/severe losses, the UCL - 5 dB method resulted in the highest phoneme recognition scores.

Evaluation of cellular phone technology with digital hearing aid features: effects of encoding and individualized amplification.

PURPOSE: To compare multichannel amplification within a cellular phone system to a standard cellular phone response. RESEARCH DESIGN: Three cellular phone speech-encoding strategies were evaluated: a narrow-band (3.5 kHz upper cutoff) enhanced variable-rate coder (EVRC), a narrow-band selectable mode vocoder (SMV), and a wide-band SMV (7.5 kHz cutoff). Because the SMV encoding strategies are not yet available on phones, the processing was simulated using a computer. Individualized-amplification settings were created using NAL-NL1 (National Acoustic Laboratories--Non-linear 1) targets. Overall gain was set at preferred listening levels for both the individualized-amplification setting and the standard cellular phone setting for each of the three encoders. Phoneme-recognition scores and subjective ratings (listening effort, overall quality) were obtained in quiet and in noise. Stimuli were played from loudspeakers in one room, picked up by a microphone connected to a (transmitting) computer, and sent over the Internet to a receiving computer in an adjacent room, where the signal was amplified and delivered monaurally. STUDY SAMPLE: Fourteen participants with hearing loss. RESULTS: Phoneme scores and subjective ratings were significantly higher for the individualized-amplification setting than for the standard setting in both quiet and noise. There were no significant differences among the cellular phone encoding strategies for any measure.

Temporal intraspeech masking of plosive bursts: effects of hearing loss and frequency shaping.

PURPOSE: The purposes were (a) to compare masking of consonant bursts by adjacent vowels for listeners with and without hearing loss and (b) to determine the extent to which the temporal intraspeech masking can be reduced by a simulated hearing-aid frequency-response shaping. METHOD: Fourteen adults with sensorineural hearing loss and 10 with normal hearing participated. Seven of the participants with hearing loss had flat or gradually sloping audiograms, and 7 had steeply sloping losses. Stimuli consisted of 3 consonant bursts (/t/, /p/, /k/) presented in isolation and in vowel-consonant-vowel combinations using the vowel /a/ with formant transition information removed. Normal-hearing listeners were tested using unfiltered stimuli. Listeners with hearing loss were tested using unfiltered stimuli and stimuli filtered to approximate a hearing aid frequency response prescribed by NAL-R. All listeners were tested under earphones at the most comfortable level for the vowel stimulus. Temporal intraspeech masking was quantified as the threshold shift produced by the adjacent vowels. RESULTS: Average intraspeech masking for listeners with steeply sloping hearing loss was significantly higher than that of normal-hearing listeners and those with flat/gradually sloping losses. Greater intraspeech masking was observed for /t/ and /p/ than for /k/. On average, frequency shaping significantly reduced the amount of intraspeech masking for listeners with steeply sloping hearing losses. Even with appropriate amplification/spectral shaping, however, temporal intraspeech masking remained greater than normal for several individuals. CONCLUSION: Findings suggest that some individuals with steeply sloping losses may need additional signal processing to supplement frequency shaping to overcome the effect of temporal intraspeech masking.

Hearing aid maximum output and loudness discomfort: are unaided loudness measures needed?

The purpose of this study was to evaluate a clinical protocol for setting hearing aid maximum output (MPO) in adult users. The protocol consisted of matching prescriptive targets for MPO followed by aided loudness validation and adjustment. Twenty-eight adults fit with multichannel hearing aids during the previous two years were recalled for unaided loudness measures. During the recall visit, unaided frequency-specific loudness discomfort levels were measured for frequencies between 250 and 3000 Hz. These values were converted to real-ear levels by adding individually measured real-ear dial differences. Real-ear saturation responses (RESR) were measured using a 90 dB pure-tone sweep and compared to the real-ear loudness discomfort levels. All participants completed the APHAB Aversiveness scale and Munro-Patel loudness questionnaire. A subset of participants (n = 20) completed the Profile of Aided Loudness. The average RESR-UCL difference was -5.7 dB, and the maximum difference was 15 dB. For all but one participant, the average RESR values (.5-3 kHz) were either less than or no more than 5 dB above the LDLs, and the aided APHAB Aversiveness scores were below the 80th percentile. There were no significant correlations between the scores on the loudness questionnaires and the differences between RESR and LDL values. Results suggest that unaided LDL measures may be redundant if aided loudness validation measures are completed.

Autonomic Nervous System Responses to Hearing-Related Demand and Evaluative Threat.

PURPOSE: This paper consists of 2 parts. The purpose of Part 1 was to review the potential influence of internal (person-related) factors on listening effort. The purpose of Part 2 was to present, in support of Part 1, preliminary data illustrating the interactive effects of an external factor (task demand) and an internal factor (evaluative threat) on autonomic nervous system measures. METHOD: For Part 1, we provided a brief narrative review of motivation and stress as modulators of listening effort. For Part 2, we described preliminary data from a study using a repeated-measures (2 × 2) design involving manipulations of task demand (high, low) and evaluative threat (high, low). The low-demand task consisted of repetition of sentences from a narrative. The high-demand task consisted of answering questions about the narrative, requiring both comprehension and recall. During the high evaluative threat condition, participants were filmed and told that their video recordings would be evaluated by a panel of experts. During the low evaluative threat condition, no filming occurred; participants were instructed to "do your best." Skin conductance (sympathetic nervous system activity) and heart rate variability (HRV, parasympathetic activity) were measured during the listening tasks. The HRV measure was the root mean square of successive differences of adjacent interbeat intervals. Twelve adults with hearing loss participated. RESULTS: Skin conductance increased and HRV decreased relative to baseline (no task) for all listening conditions. Skin conductance increased significantly with an increase in evaluative threat, but only for the more demanding task. There was no significant change in HRV in response to increasing evaluative threat or task demand. CONCLUSIONS: Listening effort may be influenced by factors other than task difficulty, as reviewed in Part 1. This idea is supported by the preliminary data indicating that the sympathetic nervous system response to task demand is modulated by social evaluative threat. More work is needed to determine the relative contributions of motivation and emotional stress on physiological responses during listening tasks.

Talker separation and sequential stream segregation in listeners with hearing loss: patterns associated with talker gender.

The purpose of this paper was to examine the relations between the ability to separate simultaneous sentences spoken by talkers of different gender and the ability to separate pitch patterns in a sequential stream segregation task. Simultaneous sentence pairs consisting of 1 sentence spoken by a male talker and 1 sentence spoken by a female talker were presented to 11 listeners with sensorineural hearing loss. Listeners were asked to repeat both sentences and were scored on the number of words repeated correctly. Separate scores were obtained for the male and female sentences. Sequential stream segregation was then measured using series of tones consisting of a fixed frequency (A) and a varying frequency tone (B). Tone series were presented in an ABA_ABA_... pattern starting at a varying frequency either below (ascending pattern) or above (descending pattern) the frequency of the fixed 1000 Hz tone. Fusion thresholds, defined as the frequency separation at which listeners could no longer perceptually separate the tones A and B, were obtained for both ascending and descending patterns. There was no significant difference between ascending and descending fusion thresholds based on the group data, but substantial individual differences were observed. Speech recognition scores for the male talker were strongly related to ascending fusion thresholds, but not descending thresholds. In contrast, speech recognition scores for the female talker were strongly related to the descending thresholds, but not the ascending thresholds. For both the male and female talkers, better recognition scores were associated with lower (nearer to normal) fusion thresholds. Results suggest that the importance of streaming in the perceptual separation of talkers may depend on the nature of the information provided by the changing pitch stream.

Limiting high-frequency hearing aid gain in listeners with and without suspected cochlear dead regions.

The purpose of this study was to compare threshold-matched ears with and without suspected cochlear dead regions in terms of the speech perception benefit from high-frequency amplification. The Threshold Equalizing Noise Test (TEN) was used to assess the presence of dead regions. Speech perception was measured while participants were wearing a hearing aid fit to approximate DSL[i/o] targets. Consonant identification of nonsense vowel-consonant-vowel combinations was measured in quiet using a forced-choice procedure. Phoneme recognition was measured at signal-to-noise ratios ranging from 0 to +15 dB using the Computer-Assisted Speech Perception Assessment test (CASPA). Recognition scores were obtained for unfiltered stimuli and stimuli that were low-pass filtered at the estimated boundary of the suspected dead regions, 1/2 octave above and 1 octave above the boundary. Filter settings for the ears without suspected dead regions were the same as settings of the threshold-matched counterpart. In quiet and in low levels of noise, speech perception scores were significantly higher for the wide-band (unfiltered) condition than for the filtered conditions, and performance was similar for the ears with and without suspected dead regions. In high levels of noise, mean scores were highest in the wide-band condition for the ears without suspected dead regions, but performance reached an asymptote for the ears with suspected dead regions. These results suggest that patients with cochlear dead regions may experience speech perception benefit from wide-band high-frequency gain in quiet and low levels of noise, but not in high levels of noise.