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Journal of the Acoustical Society of America

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May 2011

Volume 129, Issue 5, pp. EL161-3425

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The psychophysics of absolute threshold and signal duration: A probabilistic approach

Ray Meddis and Wendy Lecluyse

J. Acoust. Soc. Am. Volume 129, Issue 5, pp. 3153-3165 (2011); (13 pages) | Cited 3 times

Online Publication Date: 10 May 2011

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The absolute threshold for a tone depends on its duration; longer tones have lower thresholds. This effect has traditionally been explained in terms of “temporal integration” involving the summation of energy or perceptual information over time. An alternative probabilistic explanation of the process is formulated in terms of simple equations that predict not only the time/duration dependence but also the shape of the psychometric function at absolute threshold. It also predicts a tight relationship between these two functions. Measurements made using listeners with either normal or impaired hearing show that the probabilistic equations adequately fit observed threshold-duration functions and psychometric functions. The mathematical formulation implies that absolute threshold can be construed as a two-valued function: (a) gain and (b) sensory threshold, and both parameters can be estimated from threshold-duration data. Sensorineural hearing impairment is sometimes associated with a smaller threshold/duration effect and sometimes with steeper psychometric functions. The equations explain why these two effects are expected to be linked. The probabilistic approach has the potential to discriminate between hearing deficits involving gain reduction and those resulting from a raised sensory threshold.
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43.66.Ba Models and theories of auditory processes

Psychophysical tuning curves for frequencies below 100 Hz

Carlos Jurado, Christian S. Pedersen, and Brian C. J. Moore

J. Acoust. Soc. Am. Volume 129, Issue 5, pp. 3166-3180 (2011); (15 pages) | Cited 2 times

Online Publication Date: 10 May 2011

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Psychophysical tuning curves (PTCs) were measured for sinusoidal signals with frequency fs = 31.5, 40, 50, 63, and 80 Hz, using sinusoidal and narrowband-noise maskers. For the former, conditions were included where a pair of beating tones was added to reduce the use of cues related to beats. Estimates of each subject’s middle-ear transfer function (METF) were obtained from equal-loudness contours measured from 20 to 160 Hz. With decreasing fs, the PTCs became progressively broadened and markedly asymmetrical, with shallow upper skirts and steep lower skirts. For the sinusoidal maskers, the tips were more irregular than for narrowband-noise maskers or when beating tones were added. For fs = 31.5 and 40 Hz, the tips of the PTCs always fell above fs. Allowing for the METF so as to infer underlying filter shapes resulted in flatter lower skirts, especially below 40 Hz, and reduced the frequency at the tips for fs between 31.5 and 50 Hz; however, the tips did not fall below 40 to 50 Hz. The bandwidths of the PTCs increased with decreasing fs below 80 Hz. However, bandwidths remained roughly constant if the METF was included as part of auditory filtering for frequencies below 40 Hz.
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43.66.Ba Models and theories of auditory processes
43.66.Dc Masking
43.66.Cb Loudness, absolute threshold

Disrupting within-channel cues to comodulation masking release

Simon A. Goldman, Thomas Baer, and Brian C. J. Moore

J. Acoust. Soc. Am. Volume 129, Issue 5, pp. 3181-3193 (2011); (13 pages) | Cited 2 times

Online Publication Date: 10 May 2011

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Comodulation masking release (CMR), assessed using a flanking-band (FB) paradigm, may reflect the contribution of both across- and within-channel cues when FBs are proximal to the signal frequency. This study examined the effect of disrupting within-channel cues based upon envelope beats at the output of an auditory filter centered at the signal frequency, using a method described by Richards [(1988) Hear. Res. 35, 47–58], here called “on-frequency band (OFB) reversal.” This removed regular beats for a pair of proximal FBs centered symmetrically about the OFB on a linear frequency scale (but not for a single FB that had the same center frequency as either of the constituent FBs in a pair) while maintaining the comodulation of individual noise bands that provides the basis for across-channel processes. OFB reversal consistently reduced CMR for proximal FB pairs—but not for a single FB or distal FB pair or when the FBs were presented in the opposite ear to the signal plus OFB—across a range of signal frequencies and for continuous and gated noise presentation. Simulations indicated that OFB reversal reduces the availability of within-channel cues based upon temporal fine structure and changes in envelope statistics.
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43.66.Dc Masking
43.66.Lj Perceptual effects of sound
43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music
43.66.Ba Models and theories of auditory processes

Investigating temporal asymmetry using masking period patterns and models of peripheral auditory processing

Jennifer J. Lentz and Yi Shen

J. Acoust. Soc. Am. Volume 129, Issue 5, pp. 3194-3205 (2011); (12 pages) | Cited 1 time

Online Publication Date: 10 May 2011

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Two experiments were conducted in conjunction with modeling to evaluate the role of peripheral nonlinearity and neural adaptation in the perception of temporally asymmetric sounds. In both experiments, maskers were broadband noises amplitude modulated with ramped and damped exponential modulators that repeated at 40 Hz. Masking period patterns (MPPs) were constructed by measuring detection threshold of a 5-ms, 1000-Hz tone burst as function of the signal’s onset delay. Experiment I showed that varying modulator half-life from 1 to 16 ms led to differences in the damped and the ramped MPPs that were largest at the short half-lives and diminished at the longer half-lives. When masker level was varied (experiment II), the largest difference between ramped and damped MPPs occurred at moderate stimulus levels. Two peripheral auditory models were evaluated, one a simple auditory filter followed by a power-law nonlinearity and another, a model of auditory nerve processing [J. Acoust. Soc. Am. 126, 2390–2412 (2009)] that includes neural adaptation. Neither models predicted differences between the ramped and damped MPPs, providing indirect support that the central auditory system has a role in perceptual temporal asymmetry.
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43.66.Dc Masking
43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music

Effect of level on the discrimination of harmonic and frequency-shifted complex tones at high frequencies

Brian C. J. Moore and Aleksander Sęk

J. Acoust. Soc. Am. Volume 129, Issue 5, pp. 3206-3212 (2011); (7 pages) | Cited 4 times

Online Publication Date: 10 May 2011

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Moore and Sęk [J. Acoust. Soc. Am. 125, 3186–3193 (2009)] measured discrimination of a harmonic complex tone and a tone in which all harmonics were shifted upwards by the same amount in Hertz. Both tones were passed through a fixed bandpass filter and a background noise was used to mask combination tones. Performance was well above chance when the fundamental frequency was 800 Hz, and all audible components were above 8000 Hz. Moore and Sęk argued that this suggested the use of temporal fine structure information at high frequencies. However, the task may have been performed using excitation-pattern cues. To test this idea, performance on a similar task was measured as a function of level. The auditory filters broaden with increasing level, so performance based on excitation-pattern cues would be expected to worsen as level increases. The results did not show such an effect, suggesting that the task was not performed using excitation-pattern cues.
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43.66.Hg Pitch
43.66.Fe Discrimination: intensity and frequency

Octave illusion elicited by overlapping narrowband noises

K. Jonas Brännström and Patrik Nilsson

J. Acoust. Soc. Am. Volume 129, Issue 5, pp. 3213-3220 (2011); (8 pages)

Online Publication Date: 10 May 2011

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The octave or Deutsch illusion occurs when two tones, separated by about one octave, are presented simultaneously but alternating between ears, such that when the low tone is presented to the left ear the high tone is presented to the right ear and vice versa. Most subjects hear a single tone that alternates both between ears and in pitch; i.e., they hear a low pitched tone in one ear alternating with a high pitched tone in the other ear. The present study examined whether the illusion can be elicited by aperiodic signals consisting of low-frequency band-pass filtered noises with overlapping spectra. The amount of spectral overlap was held constant, but the high- and low-frequency content of the signals was systematically varied. The majority of subjects perceived an auditory illusion in terms of a dominant ear for pitch and lateralization by frequency, as proposed by Deutsch [(1975a) Sci. Am. 233, 92–104]. Furthermore, the salience of the illusion increased as the high frequency of the content in the signal increased. Since no harmonics were present in the stimuli, it is highly unlikely that this illusion is perceived on the basis of binaural diplacusis or harmonic binaural fusion.
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43.66.Rq Dichotic listening
43.66.Hg Pitch

A channel-selection criterion for suppressing reverberation in cochlear implants

Kostas Kokkinakis, Oldooz Hazrati, and Philipos C. Loizou

J. Acoust. Soc. Am. Volume 129, Issue 5, pp. 3221-3232 (2011); (12 pages) | Cited 8 times

Online Publication Date: 10 May 2011

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Little is known about the extent to which reverberation affects speech intelligibility by cochlear implant (CI) listeners. Experiment 1 assessed CI users’ performance using Institute of Electrical and Electronics Engineers (IEEE) sentences corrupted with varying degrees of reverberation. Reverberation times of 0.30, 0.60, 0.80, and 1.0 s were used. Results indicated that for all subjects tested, speech intelligibility decreased exponentially with an increase in reverberation time. A decaying-exponential model provided an excellent fit to the data. Experiment 2 evaluated (offline) a speech coding strategy for reverberation suppression using a channel-selection criterion based on the signal-to-reverberant ratio (SRR) of individual frequency channels. The SRR reflects implicitly the ratio of the energies of the signal originating from the early (and direct) reflections and the signal originating from the late reflections. Channels with SRR larger than a preset threshold were selected, while channels with SRR smaller than the threshold were zeroed out. Results in a highly reverberant scenario indicated that the proposed strategy led to substantial gains (over 60 percentage points) in speech intelligibility over the subjects’ daily strategy. Further analysis indicated that the proposed channel-selection criterion reduces the temporal envelope smearing effects introduced by reverberation and also diminishes the self-masking effects responsible for flattened formants.
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43.66.Ts Auditory prostheses, hearing aids
43.71.Ky Speech perception by the hearing impaired
43.71.Gv Measures of speech perception (intelligibility and quality)
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