Evelyn Davies-Venn

Effects of audibility and multichannel wide dynamic range compression on consonant recognition for listeners with severe hearing loss.

Objective: This study examined the effects of multichannel wide-dynamic range compression (WDRC) amplification and stimulus audibility on consonant recognition and error patterns. Design: Listeners had either severe or mild to moderate sensorineural hearing loss. Each listener was monaurally fit with a wearable hearing aid using typical clinical procedures, frequency-gain parameters, and a hybrid of clinically prescribed compression ratios for desired sensation level (Scollie et al., 2005) and NAL-NL (Dillon, 1999). Consonant-vowel nonsense syllables were presented in soundfield at multiple input levels (50, 65, 80 dB SPL). Test conditions were four-channel fast-acting WDRC amplification and a control compression limiting (CL) amplification condition. Listeners identified the stimulus heard from choices presented on an on-screen display. A between-subject repeated measures design was used to evaluate consonant recognition and consonant confusion patterns. Results: Fast-acting WDRC provided a considerable audibility advantage at 50 dB SPL, especially for listeners with severe hearing loss. Listeners with mild to moderate hearing loss received less audibility improvement from the fast-acting WDRC amplification, for conversational and high level speech, when compared with listeners with severe hearing loss. Analysis of WDRC benefit scores revealed that listeners had slightly lower scores with fast-acting WDRC amplification (relative to CL) when WDRC provided minimal improvement in audibility. The negative effect was greater for listeners with mild to moderate hearing loss compared with their counterparts with severe hearing loss. Conclusions: All listeners, but particularly the severe loss group, benefited from fast-acting WDRC amplification for low-level speech. For conversational and higher speech levels (i.e., when WDRC does not confer a significant audibility advantage), fast-acting WDRC amplification seems to slightly degrade performance. Listeners’ consonant confusion patterns suggest that this negative effect may be partly due to fast-acting WDRC-induced distortions, which alter specific consonant features. In support of this view, audibility accounted for a greater percentage of the variance in listeners’ performance with CL amplification compared with fast-acting WDRC amplification.

Comparing auditory filter bandwidths, spectral ripple modulation detection, spectral ripple discrimination, and speech recognition: Normal and impaired hearing

Some listeners with hearing loss show poor speech recognition scores in spite of using amplification that optimizes audibility. Beyond audibility, studies have suggested that suprathreshold abilities such as spectral and temporal processing may explain differences in amplified speech recognition scores. A variety of different methods has been used to measure spectral processing. However, the relationship between spectral processing and speech recognition is still inconclusive. This study evaluated the relationship between spectral processing and speech recognition in listeners with normal hearing and with hearing loss. Narrowband spectral resolution was assessed using auditory filter bandwidths estimated from simultaneous notched-noise masking. Broadband spectral processing was measured using the spectral ripple discrimination (SRD) task and the spectral ripple depth detection (SMD) task. Three different measures were used to assess unamplified and amplified speech recognition in quiet and noise. Stepwise multiple linear regression revealed that SMD at 2.0 cycles per octave (cpo) significantly predicted speech scores for amplified and unamplified speech in quiet and noise. Commonality analyses revealed that SMD at 2.0 cpo combined with SRD and equivalent rectangular bandwidth measures to explain most of the variance captured by the regression model. Results suggest that SMD and SRD may be promising clinical tools for diagnostic evaluation and predicting amplification outcomes.

Multi-microphone adaptive array augmented with visual cueing

We present the development of an audiovisual array that enables hearing aid users to converse with multiple speakers in reverberant environments with significant speech babble noise where their hearing aids do not function well. The system concept consists of a smartphone, a smartphone accessory, and a smartphone software application. The smartphone accessory concept is a multi-microphone audiovisual array in a form factor that allows attachment to the back of the smartphone. The accessory will also contain a lower power radio by which it can transmit audio signals to compatible hearing aids. The smartphone software application concept will use the smartphones built in camera to acquire images and perform real-time face detection using the built-in face detection support of the smartphone. The audiovisual beamforming algorithm uses the location of talking targets to improve the signal to noise ratio and consequently improve the users speech intelligibility. Since the proposed array system leverages a handheld consumer electronic device, it will be portable and low cost. A PC based experimental system was developed to demonstrate the feasibility of an audiovisual multi-microphone array and these results are presented.

Effect of musical training on EEG measures of spectro-temporal processing

Recent studies show that musical training enhances auditory processing abilities such as sensitivity to temporal fine structure and narrowband frequency resolution. Little is known about the effect of musical training on broadband spectro-temporal processing using rippled noise. This study evaluated whether musician enhancement in frequency resolution can be generalized to broadband spectro-temporal resolution using electrophysiological measures. We tested the hypothesis that musicians have enhanced broadband spectral resolution abilities compared to non-musicians. Spectral processing was measured using P1 N1 P2 responses to spectro-temporally modulated rippled noise. The test stimulus was spectro-temporally modulation wideband (4 octaves) rippled noise from 350 to 5600 Hz. EEG recordings were made using a 32-channel standard 10/20 configuration BioSemi system with a sampling rate of 4 kHz. For each condition, 1000 repetitions of the test stimuli were presented at 100% modulation with 2 Hz temporal modula...

The effects of carrier bandwidth and intensity on spectral ripple perception in listeners with hearing loss

Listeners with hearing loss often need to listen to speech signals at high intensities to ensure proper audibility. Spectral processing deteriorates at high intensities, but signal acoustics such as bandwidth and filtering can be used to mitigate this deterioration. This study evaluated the effect of carrier bandwidth on broadband spectral processing at high intensities for individuals with hearing loss. Spectral modulation detection thresholds were measured using a rippled noise carrier with varying bandwidths from 1 to 4 octaves, to assess whether individuals with hearing loss were more susceptible to the deleterious effects of high-intensity compared to their counterparts with normal hearing. Results show that spectral processing degrades at high intensities. Listeners with hearing loss benefited from the increase in signal bandwidth at high intensities much more than their counterparts with normal hearing. Our findings suggest that spectral processing for broadband signals involve within and across ch...

The effects of temporal envelope confusion on release of masking

Widened auditory filters in hearing impaired (HI) listeners may force them to rely more on temporal envelope (TE) cues when listening to speech. We propose that reduced masking release in HI listeners may be partially due to the confusion of the TEs of the masker and target. The current study investigates HI listeners comprehension of low- or high-pass vocoded spondees in the presence of fluctuating and stationary background noise. The spectral relationship of the target and masker was systematically varied from greater to no spectral overlap; the TEs of the masker and target were varied in similarity along two aspects — amplitude-modulation rate and shape. Preliminary data have shown the TE confusion in some HI impaired listeners results in speech understanding scores that are poorer in the presence of fluctuating noise (at a rate of 4Hz) than when the stationary noise is present. On the other hand, another group of HI listeners has demonstrated masking release. The effect of TE confusion of speech-en...

Investigating the effect of speech stimuli on temporal masking release

The effect of masking release is still the source of numerous active investigations. However, differences in findings are sometimes noted among studies, especially related to potential gate frequency effects. The present study investigated the effect of masking release on listeners using a variety of speech materials . The main goal of this study was to investigate the effect of speech material on measures of masking release for listeners with normal hearing and hearing loss. The test stimuli were IEEE sentences and modified spondee words. To eliminate confounds of audibility and duration, the test stimuli were equated for duration and audibility. Listeners were tested across a wide range of audibility and gate frequencies. Performance and masking release results will be presented for these speech stimuli. [Work supported by NIDCD 008306.]

Pure‐tone glide detection and simulated formant transition discrimination by listeners with hearing loss.

Listeners with hearing loss (HI) have poorer pure‐tone glide detection thresholds than normal‐hearing (NH) listeners [Nelson et al., ASA Baltimore (2009)]. Many HI listeners also experience reduced masking release for glide detection in gated noise compared to their performance in steady noise. Pure tones, however, are not good representations of formant transitions in speech. In this study, we compare listeners’ thresholds for detecting pure‐tone glides and for detecting changes in the spectral profile of a harmonic complex that mimics formant transitions. Formantlike transitions were simulated by adding intensity increments to harmonic components in the range 1–1.5 kHz. Increments were progressively delayed with increasing component frequency. Pure‐tone glides and formantlike transitions were presented in quiet, steady noise, and gated noise to NH and HI listeners. Some but not all HI listeners showed poorer spectral profile change discrimination when compared to NH listeners, despite having normal incr...