Level-dependent changes in detection of temporal gaps in noise markers by adults with normal and impaired hearing

Abstract

Compression in the basilar-membrane input-output response flattens the temporal envelope of a fluctuating signal when more gain is applied to lower level than higher level temporal components. As a result, level-dependent changes in gap detection for signals with different depths of envelope fluctuation and for subjects with normal and impaired hearing may reveal effects of compression. To test these assumptions, gap detection with and without a broadband noise was measured with 1 000-Hz-wide (flatter) and 50-Hz-wide (fluctuating) noise markers as a function of marker level. As marker level increased, background level also increased, maintaining a fixed acoustic signal-tonoise ratio (SNR) to minimize sensation-level effects on gap detection. Significant level-dependent changes in gap detection were observed, consistent with effects of cochlear compression. For the flatter marker, gap detection that declines with increases in level up to mid levels and improves with further increases in level may be explained by an effective flattening of the temporal envelope at mid levels, where compression effects are expected to be strongest. A flatter effective temporal envelope corresponds to a reduced effective SNR. The effects of a reduction in compression (resulting in larger effective SNRs) may contribute to better-than-normal gap detection observed for some hearing-impaired listeners.

Individual Differences in Behavioral Estimates of Cochlear Nonlinearities

“…TMCs were measured for a 1.0-kHz probe at 10 dB above the quiet threshold for the probe as a function of the time interval between the masker and the probe, for on-frequency (1.0 kHz) and off-frequency (0.5 kHz) maskers. The 1.0-kHz probe was selected to complement data being collected in a parallel study measuring detection of gaps in noise markers centered at 1.0 kHz (Horwitz et al 2011). Masker-probe intervals ranged from 0 to 70 ms in 10-ms steps targeting a minimum of seven masker-probe intervals.…”

Perception of Across-Frequency Asynchrony by Listeners with Cochlear Hearing Loss

“…To our knowledge, no earlier psychophysical study has explicitly addressed the effects of cochlear hearing loss on the perception of across-frequency synchrony, but a number of studies have investigated the effect of hearing loss on performance in tasks involving processing of temporal information both within and across auditory channels. The ability to detect silent gaps within stimuli, regarded as a measure of temporal resolution, has been shown to be generally unaffected by hearing loss especially when differences in stimulus audibility have been eliminated (Moore et al 1989(Moore et al , 1992Schneider et al 1994;Horwitz et al 2011). Temporal modulation transfer functions, regarded as another measure of temporal resolution, measured with tonal carriers, also suggest that HI listeners do not exhibit fundamental deficits in temporal processing (Moore and Glasberg 2001).…”

Individual and level-dependent differences in masking for adults with normal and impaired hearing

“…As reported in Horwitz et al (2011), 38 right-handed subjects participated, spanning a wide range of hearing thresholds. Participants were organized into three groups based on their quiet thresholds, defined as the average detection threshold for two noise markers (1000-Hz-wide, presented here, and 50-Hz-wide, not included here) used in the original gap detection study.…”

“…This gap detection experiment was designed and interpreted in terms of expected level-dependent changes in cochlear compression. Although not reported in Horwitz et al (2011), the experimental design called for masked detection thresholds for the noise markers to be measured over the same range of broadband noise levels as gap detection. These masked thresholds and masking slopes are relevant to the question of individual and level-dependent differences in simultaneous, on-frequency masking and are included in this letter and compared to slopes for gap detection published in Horwitz et al (2011).…”

“…Horwitz et al (2011) reported thresholds for detection of gaps in noise markers at fixed marker-to-background ratios for a range of background noise levels. This gap detection experiment was designed and interpreted in terms of expected level-dependent changes in cochlear compression.…”