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Journal of the Acoustical Society of America

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Oct 2011

Volume 130, Issue 4, pp. EL129-2575

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Masker location uncertainty reveals evidence for suppression of maskers in two-talker contexts

Kachina Allen, David Alais, Barbara Shinn-Cunningham, and Simon Carlile

J. Acoust. Soc. Am. Volume 130, Issue 4, pp. 2043-2053 (2011); (11 pages) | Cited 1 time

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In many natural settings, spatial release from masking aids speech intelligibility, especially when there are competing talkers. This paper describes a series of three experiments that investigate the role of prior knowledge of masker location on phoneme identification and spatial release from masking. In contrast to previous work, these experiments use initial stop-consonant identification as a test of target intelligibility to ensure that listeners had little time to switch the focus of spatial attention during the task. The first experiment shows that target phoneme identification was worse when a masker played from an unexpected location (increasing the consonant identification threshold by 2.6 dB) compared to when an energetically very similar and symmetrically located masker came from an expected location. In the second and third experiments, target phoneme identification was worse (increasing target threshold levels by 2.0 and 2.6 dB, respectively) when the target was played unexpectedly on the side from which the masker was expected compared to when the target came from an unexpected, symmetrical location in the hemifield opposite the expected location of the masker. These results support the idea that listeners modulate spatial attention by both focusing resources on the expected target location and withdrawing attentional resources from expected locations of interfering sources.
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43.66.Dc Masking

Fundamental frequency is critical to speech perception in noise in combined acoustic and electric hearing

Jeff Carroll, Stephanie Tiaden, and Fan-Gang Zeng

J. Acoust. Soc. Am. Volume 130, Issue 4, pp. 2054-2062 (2011); (9 pages) | Cited 3 times

Online Publication Date: 03 Oct 2011

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Cochlear implant (CI) users have been shown to benefit from residual low-frequency hearing, specifically in pitch related tasks. It remains unclear whether this benefit is dependent on fundamental frequency (F0) or other acoustic cues. Three experiments were conducted to determine the role of F0, as well as its frequency modulated (FM) and amplitude modulated (AM) components, in speech recognition with a competing voice. In simulated CI listeners, the signal-to-noise ratio was varied to estimate the 50% correct response. Simulation results showed that the F0 cue contributes to a significant proportion of the benefit seen with combined acoustic and electric hearing, and additionally that this benefit is due to the FM rather than the AM component. In actual CI users, sentence recognition scores were collected with either the full F0 cue containing both the FM and AM components or the 500-Hz low-pass speech cue containing the F0 and additional harmonics. The F0 cue provided a benefit similar to the low-pass cue for speech in noise, but not in quiet. Poorer CI users benefited more from the F0 cue than better users. These findings suggest that F0 is critical to improving speech perception in noise in combined acoustic and electric hearing.
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43.66.Hg Pitch
43.71.Ky Speech perception by the hearing impaired
43.71.Bp Perception of voice and talker characteristics
43.64.Me Effects of electrical stimulation, cochlear implant

Psychoacoustic evaluation of multichannel reproduced sounds using binaural synthesis and spherical beamforming

Wookeun Song, Wolfgang Ellermeier, and Jørgen Hald

J. Acoust. Soc. Am. Volume 130, Issue 4, pp. 2063-2075 (2011); (13 pages)

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The binaural auralization of a 3D sound field using spherical-harmonics beamforming (SHB) techniques was investigated and compared with the traditional method using a head-and-torso simulator (HATS). The new procedure was verified by comparing simulated room impulse responses with measured ones binaurally. The objective comparisons show that there is good agreement in the frequency range between 0.1 and 6.4 kHz. A listening experiment was performed to validate the SHB method subjectively and to compare it to the HATS method. Two musical excerpts, pop and classical, were used. Subjective responses were collected in two head rotation conditions (fixed and rotating) and six spatial reproduction modes, including phantom mono, stereo, and surround sound. The results show that subjective scales of width, spaciousness, and preference based on the SHB method were similar to those obtained for the HATS method, although the width and spaciousness of the stimuli processed by the SHB method were judged slightly higher than the ones using the HATS method in general. Thus, binaural synthesis using SHB may be a useful tool to reproduce a 3D sound field binaurally, while saving considerably on measurement time because head rotation can be simulated based on a single recording.
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43.66.Lj Perceptual effects of sound
43.60.Fg Acoustic array systems and processing, beam-forming
43.66.Pn Binaural hearing

Perception of interrupted speech: Effects of dual-rate gating on the intelligibility of words and sentences

Valeriy Shafiro, Stanley Sheft, and Robert Risley

J. Acoust. Soc. Am. Volume 130, Issue 4, pp. 2076-2087 (2011); (12 pages) | Cited 1 time

Online Publication Date: 03 Oct 2011

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Perception of interrupted speech and the influence of speech materials and memory load were investigated using one or two concurrent square-wave gating functions. Sentences (Experiment 1) and random one-, three-, and five-word sequences (Experiment 2) were interrupted using either a primary gating rate alone (0.5−24 Hz) or a combined primary and faster secondary rate. The secondary rate interrupted only speech left intact after primary gating, reducing the original speech to 25%. In both experiments, intelligibility increased with primary rate, but varied with memory load and speech material (highest for sentences, lowest for five-word sequences). With dual-rate gating of sentences, intelligibility with fast secondary rates was superior to that with single rates and a 25% duty cycle, approaching that of single rates with a 50% duty cycle for some low and high rates. For dual-rate gating of words, the positive effect of fast secondary gating was smaller than for sentences, and the advantage of sentences over word-sequences was not obtained in many dual-rate conditions. These findings suggest that integration of interrupted speech fragments after gating depends on the duration of the gated speech interval and that sufficiently robust acoustic-phonetic word cues are needed to access higher-level contextual sentence information.
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43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music
43.71.Es Vowel and consonant perception; perception of words, sentences, and fluent speech

Evidence of across-channel processing for spectral-ripple discrimination in cochlear implant listeners

Jong Ho Won, Gary L. Jones, Ward R. Drennan, Elyse M. Jameyson, and Jay T. Rubinstein

J. Acoust. Soc. Am. Volume 130, Issue 4, pp. 2088-2097 (2011); (10 pages) | Cited 2 times

Online Publication Date: 03 Oct 2011

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Spectral-ripple discrimination has been used widely for psychoacoustical studies in normal-hearing, hearing-impaired, and cochlear implant listeners. The present study investigated the perceptual mechanism for spectral-ripple discrimination in cochlear implant listeners. The main goal of this study was to determine whether cochlear implant listeners use a local intensity cue or global spectral shape for spectral-ripple discrimination. The effect of electrode separation on spectral-ripple discrimination was also evaluated. Results showed that it is highly unlikely that cochlear implant listeners depend on a local intensity cue for spectral-ripple discrimination. A phenomenological model of spectral-ripple discrimination, as an “ideal observer,” showed that a perceptual mechanism based on discrimination of a single intensity difference cannot account for performance of cochlear implant listeners. Spectral modulation depth and electrode separation were found to significantly affect spectral-ripple discrimination. The evidence supports the hypothesis that spectral-ripple discrimination involves integrating information from multiple channels.
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43.66.Ts Auditory prostheses, hearing aids
43.66.Fe Discrimination: intensity and frequency
43.66.Ba Models and theories of auditory processes

A cautionary note on the use of the adaptive up–down method

Miguel A. García-Pérez

J. Acoust. Soc. Am. Volume 130, Issue 4, pp. 2098-2107 (2011); (10 pages) | Cited 2 times

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Up–down staircases with equal sizes for the steps up and down are widely used to estimate detection and discrimination thresholds in psychoacoustics, but the conventional average-of-reversals estimator does not converge on its presumed percent point in Yes–No tasks or in two-alternative forced-choice detection tasks. The particular percent point of convergence is partly determined by the relative size of the steps with respect to the spread (inverse of slope) of the underlying psychometric function. In particular, threshold is increasingly underestimated as the spread of the psychometric function decreases. This characteristic may have serious consequences when thresholds estimated via up–down staircases are compared across conditions in which the spread of the psychometric function varies, because then these thresholds do not represent comparable measures of performance. This paper documents the misbehavior of the average-of-reversals estimator under up–down rules and types of forced-choice task that are in common use in psychoacoustics but which have not been studied before in simulations. It is also shown that a relatively simple modification of the up–down design (namely, using steps up and down of different size and in a certain ratio depending only on the task and the up–down rule being used) stabilizes the performance of these staircases.
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43.66.Yw Instruments and methods related to hearing and its measurement
43.66.Gf Detection and discrimination of sound by animals
43.64.Yp Instruments and methods
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