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May 2010

Volume 127, Issue 5, pp. EL179-3296

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Measurement of the binaural auditory filter using a detection task

Andrew J. Kolarik and John F. Culling

J. Acoust. Soc. Am. Volume 127, Issue 5, pp. 3009-3017 (2010); (9 pages) | Cited 1 time

Online Publication Date: 12 May 2010

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The spectral resolution of the binaural system was measured using a tone-detection task in a binaural analog of the notched-noise technique. Three listeners performed 2-interval, 2-alternative, forced choice tasks with a 500-ms out-of-phase signal within 500 ms of broadband masking noise consisting of an “outer” band of either interaurally uncorrelated or anticorrelated noise, and an “inner” band of interaurally correlated noise. Three signal frequencies were tested (250, 500, and 750 Hz), and the asymmetry of the filter was measured by keeping the signal at a constant frequency and moving the correlated noise band relative to the signal. Thresholds were taken for bandwidths of correlated noise ranging from 0 to 400 Hz. The equivalent rectangular bandwidth of the binaural filter was found to increase with signal frequency, and estimates tended to be larger than monaural bandwidths measured for the same listeners using equivalent techniques.
Show PACS
43.66.Ba Models and theories of auditory processes
43.66.Dc Masking
43.66.Pn Binaural hearing

Effects of background noise level on behavioral estimates of basilar-membrane compression

Melanie J. Gregan, Peggy B. Nelson, and Andrew J. Oxenham

J. Acoust. Soc. Am. Volume 127, Issue 5, pp. 3018-3025 (2010); (8 pages) | Cited 3 times

Online Publication Date: 12 May 2010

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Hearing-impaired (HI) listeners often show poorer performance on psychoacoustic tasks than do normal-hearing (NH) listeners. Although some such deficits may reflect changes in suprathreshold sound processing, others may be due to stimulus audibility and the elevated absolute thresholds associated with hearing loss. Masking noise can be used to raise the thresholds of NH to equal the thresholds in quiet of HI listeners. However, such noise may have other effects, including changing peripheral response characteristics, such as the compressive input-output function of the basilar membrane in the normal cochlea. This study estimated compression behaviorally across a range of background noise levels in NH listeners at a 4 kHz signal frequency, using a growth of forward masking paradigm. For signals 5 dB or more above threshold in noise, no significant effect of broadband noise level was found on estimates of compression. This finding suggests that broadband noise does not significantly alter the compressive response of the basilar membrane to sounds that are presented well above their threshold in the noise. Similarities between the performance of HI listeners and NH listeners in threshold-equalizing noise are therefore unlikely to be due to a linearization of basilar-membrane responses to suprathreshold stimuli in the NH listeners.
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43.66.Dc Masking
43.66.Ba Models and theories of auditory processes

Stimulus uncertainty and insensitivity to pitch-change direction

Samuel R. Mathias, Christophe Micheyl, and Peter J. Bailey

J. Acoust. Soc. Am. Volume 127, Issue 5, pp. 3026-3037 (2010); (12 pages)

Online Publication Date: 12 May 2010

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In a series of experiments, Semal and Demany [(2006). J. Acoust. Soc. Am. 120, 3907–3915] demonstrated that some normally hearing listeners are unable to determine the direction of small but detectable differences in frequency between pure tones. Unlike studies demonstrating similar effects in patients with brain damage, the authors used stimuli in which the standard frequency of the tones was highly uncertain (roved) over trials. In Experiment 1, listeners were identified as insensitive to the direction of pitch changes using stimuli with frequency roving. When listeners were retested using stimuli without roving in Experiment 2, impairments in pitch-direction identification were generally much less profound. In Experiment 3, frequency-roving range had a systematic effect on listeners’ thresholds, and impairments in pitch-direction identification tended to occur only when the roving range was widest. In Experiment 4, the influence of frequency roving was similar for continuous frequency changes as for discrete changes. Possible explanations for the influence of roving on listeners’ insensitivity to pitch-change direction are discussed.
Show PACS
43.66.Fe Discrimination: intensity and frequency
43.66.Hg Pitch

Perceptual interactions in the loudness of combined auditory and vibrotactile stimuli

E. Courtenay Wilson, Louis D. Braida, and Charlotte M. Reed

J. Acoust. Soc. Am. Volume 127, Issue 5, pp. 3038-3043 (2010); (6 pages)

Online Publication Date: 12 May 2010

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The loudness of auditory (A), tactile (T), and auditory-tactile (A+T) stimuli was measured at supra-threshold levels. Auditory stimuli were pure tones presented binaurally through headphones; tactile stimuli were sinusoids delivered through a single-channel vibrator to the left middle fingertip. All stimuli were presented together with a broadband auditory noise. The A and T stimuli were presented at levels that were matched in loudness to that of the 200-Hz auditory tone at 25 dB sensation level. The 200-Hz auditory tone was then matched in loudness to various combinations of auditory and tactile stimuli (A+T), and purely auditory stimuli (A+A). The results indicate that the matched intensity of the 200-Hz auditory tone is less when the A+T and A+A stimuli are close together in frequency than when they are separated by an octave or more. This suggests that A+T integration may operate in a manner similar to that found in auditory critical band studies, further supporting a strong frequency relationship between the auditory and somatosensory systems.
Show PACS
43.66.Lj Perceptual effects of sound
43.66.Wv Vibration and tactile senses

Integration of auditory and vibrotactile stimuli: Effects of frequency

E. Courtenay Wilson, Charlotte M. Reed, and Louis D. Braida

J. Acoust. Soc. Am. Volume 127, Issue 5, pp. 3044-3059 (2010); (16 pages)

Online Publication Date: 12 May 2010

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Perceptual integration of vibrotactile and auditory sinusoidal tone pulses was studied in detection experiments as a function of stimulation frequency. Vibrotactile stimuli were delivered through a single channel vibrator to the left middle fingertip. Auditory stimuli were presented diotically through headphones in a background of 50 dB sound pressure level broadband noise. Detection performance for combined auditory-tactile presentations was measured using stimulus levels that yielded 63% to 77% correct unimodal performance. In Experiment 1, the vibrotactile stimulus was 250 Hz and the auditory stimulus varied between 125 and 2000 Hz. In Experiment 2, the auditory stimulus was 250 Hz and the tactile stimulus varied between 50 and 400 Hz. In Experiment 3, the auditory and tactile stimuli were always equal in frequency and ranged from 50 to 400 Hz. The highest rates of detection for the combined-modality stimulus were obtained when stimulating frequencies in the two modalities were equal or closely spaced (and within the Pacinian range). Combined-modality detection for closely spaced frequencies was generally consistent with an algebraic sum model of perceptual integration; wider-frequency spacings were generally better fit by a Pythagorean sum model. Thus, perceptual integration of auditory and tactile stimuli at near-threshold levels appears to depend both on absolute frequency and relative frequency of stimulation within each modality.
Show PACS
43.66.Lj Perceptual effects of sound
43.66.Wv Vibration and tactile senses

Phase effects on the perceived elevation of complex tones

William M. Hartmann, Virginia Best, Johahn Leung, and Simon Carlile

J. Acoust. Soc. Am. Volume 127, Issue 5, pp. 3060-3072 (2010); (13 pages)

Online Publication Date: 12 May 2010

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Free-field source localization experiments with 30 source locations, symmetrically distributed in azimuth, elevation, and front-back location, were performed with periodic tones having different phase relationships among their components. Although the amplitude spectra were the same for these different kinds of stimuli, the tones with certain phase relationships were successfully localized while the tones with other phases led to large elevation errors and front-back reversals, normally growing with stimulus level. The results show that it is not enough to have a smooth, broadband, long-term signal spectrum for successful sagittal-plane localization. Instead, temporal factors are important. A model calculation investigates the idea that the tonotopic details that mediate localization need to be simultaneously, or almost simultaneously, accessible in the auditory system in order to achieve normal elevation perception. A qualitative model based on lateral inhibition seems capable in principle of accounting for both the phase effects and level effects.
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43.66.Nm Phase effects
43.66.Qp Localization of sound sources
43.66.Ba Models and theories of auditory processes

The binaural intelligibility level difference in hearing-impaired listeners: The role of supra-threshold deficits

S. Theo Goverts and Tammo Houtgast

J. Acoust. Soc. Am. Volume 127, Issue 5, pp. 3073-3084 (2010); (12 pages) | Cited 3 times

Online Publication Date: 12 May 2010

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Reduced binaural performance of hearing-impaired listeners may not only be caused by raised hearing thresholds (reduced audibility), but also by supra-threshold coding deficits in signal cues. This question was investigated in the present study using binaural intelligibility level difference (BILD) comparisons: the improvement of speech-reception threshold scores for N0Sπ relative to N0S0 presentation conditions. Investigated was what types of supra-threshold deficits play a role in reducing BILDs in hearing-impaired subjects. BILDs were investigated for 25 mild to moderate sensorineural hearing-impaired listeners, under conditions where optimal audibility was assured. All stimuli were bandpass filtered (250–4000 Hz). A distortion-sensitivity approach was used to investigate the sensitivity of subjects BILDs to external stimulus perturbations in the phase, frequency, time, and intensity domains. The underlying assumption of this approach was that an auditory coding deficit occurring in a signal cue in a particular domain will result in a low sensitivity to external perturbations applied in that domain. Compared to reference data for listeners with normal BILDs, distortion-sensitivity data for a subgroup of eight listeners with reduced BILDs suggests that these reductions in BILD were caused by coding deficits in the phase and time domains.
Show PACS
43.66.Pn Binaural hearing
43.60.Hj Time-frequency signal processing, wavelets
43.71.Ky Speech perception by the hearing impaired

Binaural interference in the free field

Naomi B. H. Croghan and D. Wesley Grantham

J. Acoust. Soc. Am. Volume 127, Issue 5, pp. 3085-3091 (2010); (7 pages) | Cited 4 times

Online Publication Date: 12 May 2010

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In an anechoic chamber the minimum audible angle (MAA) was measured in seven normal-hearing adults for a narrow band of noise centered at 4000 Hz (target). In the absence of an interfering stimulus, the average MAA was 2.1°. When a low-frequency interferer (a narrow band of noise centered at 500 Hz) was pulsed on and off with the target from directly in front of the subject, the average MAA was significantly elevated (13.4°). However, if the interferer was continuously present, or if it consisted of two independent noises presented from ±90°, interference was much reduced. The interference effect was asymmetric: a high-frequency interferer did not result in elevation of MAA threshold for a low-frequency target. These results are similar to those that have been extensively reported for stimuli under headphones [ Bernstein and Trahiotis (1995). J. Acoust. Soc. Am. 98, 155–163 ]. These data are consistent with the notion that interference from a spectrally remote low-frequency interferer occurs in the free field to the extent that the target and interferer are fused into a single perceptual object. If cues are provided that promote perceptual segregation (such as temporal onset differences or spatial location differences), the interference is reduced or eliminated.
Show PACS
43.66.Pn Binaural hearing
43.66.Dc Masking
43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music

Temporal weighting of binaural cues revealed by detection of dynamic interaural differences in high-rate Gabor click trains

G. Christopher Stecker and Andrew D. Brown

J. Acoust. Soc. Am. Volume 127, Issue 5, pp. 3092-3103 (2010); (12 pages) | Cited 5 times

Online Publication Date: 12 May 2010

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Listeners detected interaural differences of time (ITDs) or level (ILDs) carried by single 4000-Hz Gabor clicks (Gaussian-windowed tone bursts) and trains of 16 such clicks repeating at an interclick interval (ICI) of 2, 5, or 10 ms. In separate conditions, target interaural differences favored the right ear by a constant amount for all clicks (condition RR), attained their peak value at onset and diminished linearly to 0 at offset (condition R0), or grew linearly from 0 at onset to a peak value at offset (condition 0R). Threshold ITDs and ILDs were determined adaptively in separate experiments for each of these conditions and for single clicks. ITD thresholds were found to be lower for 16-click trains than for single clicks at 10-ms ICI, regardless of stimulus condition. At 2-ms ICI, thresholds in RR and R0 conditions were similar to single click thresholds at 2-ms ICI; thresholds in the 0R condition were significantly worse than for single clicks at 2-ms ICI, consistent with strong rate-dependent onset dominance in listeners’ temporal weighting of ITD. ILD thresholds, in contrast, were predominantly unaffected by ICI, suggesting little or no onset dominance for ILD of high-rate stimuli.
Show PACS
43.66.Pn Binaural hearing
43.66.Qp Localization of sound sources
43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music

Sound source localization by the plainfin midshipman fish, Porichthys notatus

David G. Zeddies, Richard R. Fay, Peter W. Alderks, Kiel S. Shaub, and Joseph A. Sisneros

J. Acoust. Soc. Am. Volume 127, Issue 5, pp. 3104-3113 (2010); (10 pages)

Online Publication Date: 12 May 2010

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The aim of this study was to use plainfin midshipman fish (Porichthys notatus) as a general model to explore how fishes localize an underwater sound source in the relatively simple geometry of a monopole sound field. The robust phonotaxic responses displayed by gravid females toward a monopole sound projector (J-9) broadcasting a low-frequency (90 Hz) tone similar to the fundamental frequency of the male’s advertisement call were examined. The projector’s sound field was mapped at 5 cm resolution azimuth using an eight-hydrophone array. Acoustic pressure was measured with the array and acoustic particle motion was calculated from pressure gradients between hydrophones. The response pathways of the fish were analyzed from video recordings and compared to the sound field. Gravid females at initial release were directed toward the sound source, and the majority (73%) swam to the playback projector with straight to slightly curved tracks in the direction of the source and in line with local particle motion vectors. In contrast, the initial direction of the control (sound-off) group did not differ from random. This paper reports on a comparison of fish localization behavior with directional cues available in the form of local particle motion vectors.
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43.66.Qp Localization of sound sources
43.64.Bt Models and theories of the auditory system
43.80.Lb Sound reception by animals: anatomy, physiology, auditory capacities, processing

Temporal pitch perception at high rates in cochlear implants

Ying-Yee Kong and Robert P. Carlyon

J. Acoust. Soc. Am. Volume 127, Issue 5, pp. 3114-3123 (2010); (10 pages) | Cited 1 time

Online Publication Date: 12 May 2010

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A recent study reported that a group of Med-El COMBI 40+CI (cochlear implant) users could, in a forced-choice task, detect changes in the rate of a pulse train for rates higher than the 300 pps “upper limit” commonly reported in the literature [ Kong, Y.-Y., et al. (2009). J. Acoust. Soc. Am. 125, 1649–1657 ]. The present study further investigated the upper limit of temporal pitch in the same group of CI users on three tasks [pitch ranking, rate discrimination, and multidimensional scaling (MDS)]. The patterns of results were consistent across the three tasks and all subjects could follow rate changes above 300 pps. Two subjects showed exceptional ability to follow temporal pitch change up to about 900 pps. Results from the MDS study indicated that, for the two listeners tested, changes in pulse rate over the range of 500–840 pps were perceived along a perceptual dimension that was orthogonal to the place of excitation. Some subjects showed a temporal pitch reversal at rates beyond their upper limit of pitch and some showed a reversal within a small range of rates below the upper limit. These results are discussed in relation to the possible neural bases for temporal pitch processing at high rates.
Show PACS
43.66.Ts Auditory prostheses, hearing aids

Adaptive environment classification system for hearing aids

Luc Lamarche, Christian Giguère, Wail Gueaieb, Tyseer Aboulnasr, and Hisham Othman

J. Acoust. Soc. Am. Volume 127, Issue 5, pp. 3124-3135 (2010); (12 pages)

Online Publication Date: 12 May 2010

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An adaptive sound classification framework is proposed for hearing aid applications. The long-term goal is to develop fully trainable instruments in which both the acoustical environments encountered in daily life and the hearing aid settings preferred by the user in each environmental class could be learned. Two adaptive classifiers are described, one based on minimum distance clustering and one on Bayesian classification. Through unsupervised learning, the adaptive systems allow classes to split or merge based on changes in the ongoing acoustical environments. Performance was evaluated using real-world sounds from a wide range of acoustical environments. The systems were first initialized using two classes, Speech and Noise, followed by a testing period when a third class, Music, was introduced. Both systems were successful in detecting the presence of an additional class and estimating its underlying parameters, reaching a testing accuracy close to the target rates obtained from best-case scenarios derived from non-adaptive supervised versions of the classifiers (about 3% lower performance). The adaptive Bayesian classifier resulted in a 4% higher overall accuracy upon splitting adaptation than the minimum distance classifier. Merging accuracy was found to be the same in the two systems and within 1%–2% of the best-case supervised versions.
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43.66.Ts Auditory prostheses, hearing aids
43.60.Mn Adaptive processing
43.60.Np Acoustic signal processing techniques for neural nets and learning systems

Multi-microphone adaptive noise reduction strategies for coordinated stimulation in bilateral cochlear implant devices

Kostas Kokkinakis and Philipos C. Loizou

J. Acoust. Soc. Am. Volume 127, Issue 5, pp. 3136-3144 (2010); (9 pages)

Online Publication Date: 12 May 2010

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Bilateral cochlear implant (BI-CI) recipients achieve high word recognition scores in quiet listening conditions. Still, there is a substantial drop in speech recognition performance when there is reverberation and more than one interferers. BI-CI users utilize information from just two directional microphones placed on opposite sides of the head in a so-called independent stimulation mode. To enhance the ability of BI-CI users to communicate in noise, the use of two computationally inexpensive multi-microphone adaptive noise reduction strategies exploiting information simultaneously collected by the microphones associated with two behind-the-ear (BTE) processors (one per ear) is proposed. To this end, as many as four microphones are employed (two omni-directional and two directional) in each of the two BTE processors (one per ear). In the proposed two-microphone binaural strategies, all four microphones (two behind each ear) are being used in a coordinated stimulation mode. The hypothesis is that such strategies combine spatial information from all microphones to form a better representation of the target than that made available with only a single input. Speech intelligibility is assessed in BI-CI listeners using IEEE sentences corrupted by up to three steady speech-shaped noise sources. Results indicate that multi-microphone strategies improve speech understanding in single- and multi-noise source scenarios.
Show PACS
43.66.Ts Auditory prostheses, hearing aids
43.66.Pn Binaural hearing
43.71.Ky Speech perception by the hearing impaired

A simulation study of harmonics regeneration in noise reduction for electric and acoustic stimulation

Yi Hu

J. Acoust. Soc. Am. Volume 127, Issue 5, pp. 3145-3153 (2010); (9 pages) | Cited 1 time

Online Publication Date: 12 May 2010

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Recent research results show that combined electric and acoustic stimulation (EAS) significantly improves speech recognition in noise, and it is generally established that access to the improved F0 representation of target speech, along with the glimpse cues, provide the EAS benefits. Under noisy listening conditions, noise signals degrade these important cues by introducing undesired temporal-frequency components and corrupting harmonics structure. In this study, the potential of combining noise reduction and harmonics regeneration techniques was investigated to further improve speech intelligibility in noise by providing improved beneficial cues for EAS. Three hypotheses were tested: (1) noise reduction methods can improve speech intelligibility in noise for EAS; (2) harmonics regeneration after noise reduction can further improve speech intelligibility in noise for EAS; and (3) harmonics sideband constraints in frequency domain (or equivalently, amplitude modulation in temporal domain), even deterministic ones, can provide additional benefits. Test results demonstrate that combining noise reduction and harmonics regeneration can significantly improve speech recognition in noise for EAS, and it is also beneficial to preserve the harmonics sidebands under adverse listening conditions. This finding warrants further work into the development of algorithms that regenerate harmonics and the related sidebands for EAS processing under noisy conditions.
Show PACS
43.66.Ts Auditory prostheses, hearing aids
43.71.Ky Speech perception by the hearing impaired
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