Benefits of Text Supplementation on Sentence Recognition and Subjective Ratings With and Without Facial Cues for Listeners With Normal Hearing.

OBJECTIVES: Recognizing speech through telecommunication can be challenging in unfavorable listening conditions. Text supplementation or provision of facial cues can facilitate speech recognition under some circumstances. However, our understanding of the combined benefit of text and facial cues in telecommunication is limited. The purpose of this study was to investigate the potential benefit of text supplementation for sentence recognition scores and subjective ratings of spoken speech with and without facial cues available. DESIGN: Twenty adult females (M = 24 years, range 21 to 29 years) with normal hearing performed a sentence recognition task and also completed a subjective rating questionnaire in 24 conditions. The conditions varied by integrity of the available facial cues (clear facial cues, slight distortion facial cues, great distortion facial cues, no facial cues), signal-to-noise ratio (quiet, +1 dB, -3 dB), and text availability (with text, without text). When present, the text was an 86 to 88% accurate transcription of the auditory signal presented at a 500 ms delay relative to the auditory signal. RESULTS: The benefits of text supplementation were largest when facial cues were not available and when the signal-to-noise ratio was unfavorable. Although no recognition score benefit was present in quiet, recognition benefit was significant in all levels of background noise for all levels of facial cue integrity. Moreover, participant subjective ratings of text benefit were robust and present even in the absence of recognition benefit. Consistent with previous literature, facial cues were beneficial for sentence recognition scores in the most unfavorable signal-to-noise ratio, even when greatly distorted. It is interesting that, although all levels of facial cues were beneficial for recognition scores, participants rated a significant benefit only with clear facial cues. CONCLUSIONS: The benefit of text for auditory-only and auditory-visual speech recognition is evident in recognition scores and subjective ratings; the benefit is larger and more robust for subjective ratings than for scores. Therefore, text supplementation might provide benefit that extends beyond speech recognition scores. Combined, these findings support the use of text supplementation in telecommunication, even when facial cues are concurrently present, such as during teleconferencing or watching television.

How directional microphones affect speech recognition, listening effort and localisation for listeners with moderate-to-severe hearing loss.

OBJECTIVE: The purpose of this study was to evaluate the effects of directional microphone use on laboratory measures of sentence recognition, listening effort and localisation. An additional purpose of this study was to evaluate the effects of asymmetric directional microphone use on the same laboratory measures. DESIGN: Three hearing aid conditions were evaluated: (1) bilateral omnidirectional microphones, (2) bilateral directional microphones and (3) asymmetric microphones (directional microphone for only one hearing aid). Sentence recognition performance was evaluated using a connected speech test. Listening effort was evaluated using a dual-task paradigm with a response time-based secondary task requiring word categorisation. Localisation was examined using a complex task requiring localisation and recall of speech originating from one of four loudspeakers in the horizontal plane (-60°, -45°, +45°, +60°). STUDY SAMPLE: Eighteen adults (M = 61.8 years) with symmetrical, moderate-to-severe hearing loss participated. RESULTS: Performance on each task was analysed separately using a repeated measures analysis of variance. Results revealed directional benefits for sentence recognition and listening effort, but microphone setting did not affect localisation. Performance was equivalent with symmetric and asymmetric directional configurations. CONCLUSIONS: Bilateral and asymmetric directional microphone configurations equally improved sentence recognition and listening effort; neither affected localisation or recall.

Child-Adult Differences in Using Dual-Task Paradigms to Measure Listening Effort.

PURPOSE: The purpose of the project was to investigate the effects modifying the secondary task in a dual-task paradigm to measure objective listening effort. To be specific, the complexity and depth of processing were increased relative to a simple secondary task. METHOD: Three dual-task paradigms were developed for school-age children. The primary task was word recognition. The secondary task was a physical response to a visual probe (simple task), a physical response to a complex probe (increased complexity), or word categorization (increased depth of processing). Sixteen adults (22-32 years, M = 25.4) and 22 children (9-17 years, M = 13.2) were tested using the 3 paradigms in quiet and noise. RESULTS: For both groups, manipulations of the secondary task did not affect word recognition performance. For adults, increasing depth of processing increased the calculated effect of noise; however, for children, results with the deep secondary task were the least stable. CONCLUSIONS: Manipulations of the secondary task differentially affected adults and children. Consistent with previous findings, increased depth of processing enhanced paradigm sensitivity for adults. However, younger participants were more likely to demonstrate the expected effects of noise on listening effort using a secondary task that did not require deep processing.

The Effects of Directional Processing on Objective and Subjective Listening Effort.

Purpose: The purposes of this investigation were (a) to evaluate the effects of hearing aid directional processing on subjective and objective listening effort and (b) to investigate the potential relationships between subjective and objective measures of effort. Method: Sixteen adults with mild to severe hearing loss were tested with study hearing aids programmed with 3 settings: omnidirectional, fixed directional, and bilateral beamformer. A dual-task paradigm and subjective ratings were used to assess objective and subjective listening effort, respectively, in 2 signal-to-noise ratios. Testing occurred in rooms with either low or moderate reverberation. Results: Directional processing improved subjective and objective listening effort, although benefit for objective effort was found only in moderate reverberation. Subjective reports of work and tiredness were more highly correlated with word recognition performance than objective listening effort. However, subjective ratings about control were significantly correlated with objective listening effort. Conclusions: Directional microphone technology in hearing aids has the potential to improve listening effort in moderately reverberant environments. In addition, subjective questions that probe a listener's desire to exercise control may be a viable method for eliciting ratings that are significantly related to objective listening effort.

The effect of changing the secondary task in dual-task paradigms for measuring listening effort.

OBJECTIVES: The purpose of this study was to evaluate the effect of changing the secondary task in dual-task paradigms that measure listening effort. Specifically, the effects of increasing the secondary task complexity or the depth of processing on a paradigm's sensitivity to changes in listening effort were quantified in a series of two experiments. Specific factors investigated within each experiment were background noise and visual cues. DESIGN: Participants in Experiment 1 were adults with normal hearing (mean age 23 years) and participants in Experiment 2 were adults with mild sloping to moderately severe sensorineural hearing loss (mean age 60.1 years). In both experiments, participants were tested using three dual-task paradigms. These paradigms had identical primary tasks, which were always monosyllable word recognition. The secondary tasks were all physical reaction time measures. The stimulus for the secondary task varied by paradigm and was a (1) simple visual probe, (2) a complex visual probe, or (3) the category of word presented. In this way, the secondary tasks mainly varied from the simple paradigm by either complexity or depth of speech processing. Using all three paradigms, participants were tested in four conditions, (1) auditory-only stimuli in quiet, (2) auditory-only stimuli in noise, (3) auditory-visual stimuli in quiet, and (4) auditory-visual stimuli in noise. During auditory-visual conditions, the talker's face was visible. Signal-to-noise ratios used during conditions with background noise were set individually so word recognition performance was matched in auditory-only and auditory-visual conditions. In noise, word recognition performance was approximately 80% and 65% for Experiments 1 and 2, respectively. RESULTS: For both experiments, word recognition performance was stable across the three paradigms, confirming that none of the secondary tasks interfered with the primary task. In Experiment 1 (listeners with normal hearing), analysis of median reaction times revealed a significant main effect of background noise on listening effort only with the paradigm that required deep processing. Visual cues did not change listening effort as measured with any of the three dual-task paradigms. In Experiment 2 (listeners with hearing loss), analysis of median reaction times revealed expected significant effects of background noise using all three paradigms, but no significant effects of visual cues. CONCLUSIONS: None of the dual-task paradigms were sensitive to the effects of visual cues. Furthermore, changing the complexity of the secondary task did not change dual-task paradigm sensitivity to the effects of background noise on listening effort for either group of listeners. However, the paradigm whose secondary task involved deeper processing was more sensitive to the effects of background noise for both groups of listeners. While this paradigm differed from the others in several respects, depth of processing may be partially responsible for the increased sensitivity. Therefore, this paradigm may be a valuable tool for evaluating other factors that affect listening effort.

Increasing motivation changes subjective reports of listening effort and choice of coping strategy.

OBJECTIVE: The purpose of this project was to examine the effect of changing motivation on subjective ratings of listening effort and on the likelihood that a listener chooses either a controlling or an avoidance coping strategy. DESIGN: Two experiments were conducted, one with auditory-only (AO) and one with auditory-visual (AV) stimuli, both using the same speech recognition in noise materials. Four signal-to-noise ratios (SNRs) were used, two in each experiment. The two SNRs targeted 80% and 50% correct performance. Motivation was manipulated by either having participants listen carefully to the speech (low motivation), or listen carefully to the speech and then answer quiz questions about the speech (high motivation). STUDY SAMPLE: Sixteen participants with normal hearing participated in each experiment. Eight randomly selected participants participated in both. RESULTS: Using AO and AV stimuli, motivation generally increased subjective ratings of listening effort and tiredness. In addition, using auditory-visual stimuli, motivation generally increased listeners' willingness to do something to improve the situation, and decreased their willingness to avoid the situation. CONCLUSIONS: These results suggest a listener's mental state may influence listening effort and choice of coping strategy.

High-frequency amplification and sound quality in listeners with normal through moderate hearing loss.

PURPOSE: One factor that has been shown to greatly affect sound quality is audible bandwidth. Provision of gain for frequencies above 4-6 kHz has not generally been supported for groups of hearing aid wearers. The purpose of this study was to determine if preference for bandwidth extension in hearing aid processed sounds was related to the magnitude of hearing loss in individual listeners. METHOD: Ten participants with normal hearing and 20 participants with mild-to-moderate hearing loss completed the study. Signals were processed using hearing aid-style compression algorithms and filtered using two cutoff frequencies, 5.5 and 9 kHz, which were selected to represent bandwidths that are achievable in modern hearing aids. Round-robin paired comparisons based on the criteria of preferred sound quality were made for 2 different monaurally presented brief sound segments, including music and a movie. RESULTS: Results revealed that preference for either the wider or narrower bandwidth (9- or 5.5-kHz cutoff frequency, respectively) was correlated with the slope of hearing loss from 4 to 12 kHz, with steep threshold slopes associated with preference for narrower bandwidths. CONCLUSION: Consistent preference for wider bandwidth is present in some listeners with mild-to-moderate hearing loss.

The effect of digital phase cancellation feedback reduction systems on amplified sound quality.

The effect of feedback reduction (FBR) systems on sound quality recorded from two commercially available hearing aids was evaluated using paired comparison judgments by 16 participants with mild to severe sloping hearing loss. These comparisons were made with the FBR systems on and off without audible feedback and while attempting to control for differences in gain and clinical fitting factors. Wilcoxon signed rank test analyses showed that the participants were unable to differentiate between signals that had been recorded with the FBR systems on and off within the same hearing aid. However, significant between-instrument differences in sound quality were identified. The results support the activation of the FFT-phase cancellation FBR systems evaluated herein without concern for a noticeable degradation of sound quality.

Speech recognition for unilateral and bilateral cochlear implant modes in the presence of uncorrelated noise sources.

OBJECTIVE: The purpose of the current investigation was to compare speech recognition in noise for bilateral and unilateral modes within postlingually deafened, adult bilateral cochlear implant recipients. In addition, it was of interest to evaluate the time course of the bilateral speech-recognition advantage and the effect of changing signal-to-noise ratio (SNR) on the magnitude of the bilateral advantage. DESIGN: In the first experiment, 16 postlingually deafened adults who were bilaterally implanted with the MED-EL C40+ cochlear device were evaluated in unilateral left, unilateral right, and bilateral conditions 4 to 7 mo after activation. Speech recognition in the presence of five spatially separated, uncorrelated noise sources was evaluated using both a single fixed SNR of +10 dB and an adaptive-SNR method. In a follow-up study, a subset of 10 participants was re-evaluated using an identical fixed-SNR method 12 to 17 mo after activation to examine the time course of speech-recognition performance in both unilateral and bilateral modes at a single SNR. A third study was performed with a subset of six participants to examine performance over a range of SNRs. In this study, speech recognition was measured 12 to 17 mo after activation in quiet and at +5, +10, +15, and +20 dB SNRs using the same five uncorrelated noise sources. RESULTS: The speech-recognition data revealed a significant bilateral advantage of 3.3 dB using the adaptive-SNR method. A significant bilateral advantage of 9% was also measured using a fixed +10 dB SNR. Results from the second study revealed that experience resulted in a significant (11 to 20%) increase in speech-recognition-in-noise performance for both unilateral and bilateral modes; however, the magnitude of the bilateral advantage was not affected by experience. Results from the third study revealed the largest bilateral advantage at the poorest SNR evaluated. In addition, performance in quiet was significantly better than that measured in the presence of noise, even at the +20 dB SNR. CONCLUSIONS: The results of these experiments support a small but significant bilateral speech-recognition-in-noise advantage for cochlear implant recipients in an environment with multiple noise sources. This advantage is presumed to be attributable to the combined effects of binaural squelch and diotic summation. Although experience generally improved speech-recognition-in-noise performance in both unilateral and bilateral modes, a consistent bilateral advantage (approximately 10%) was measured at 4 to 7 mo and at 12 to 17 mo postactivation.

Directional hearing aid benefit in listeners with severe hearing loss.

The purpose of this investigation was to examine the potential for directional hearing aid benefit in listeners with severe hearing loss at multiple SNRs for both auditory only and audio-visual presentation modes. Speech recognition performance was measured using the connected speech test at six SNRs individually determined for each subject in order to avoid floor and ceiling effects. The results revealed significant directional benefit was present at all tested SNRs in the presence of visual information. For auditory only presentations, significant directional benefit was only present at the least positive SNR. The largest directional benefit was measured at the poorest tested SNR for both auditory only and audiovisual presentation modes. The results of this study generally support small but significant directional for listeners with severe hearing loss benefit in a difficult listening environment both with and without the presence of visual information.