摘要:

Previous work suggests that, for some listeners, masker fluctuation may be advantageous for NoSπ detection. This study tested the hypothesis that the benefit of masker fluctuation to binaural analysis is based on the ability to take advantage of epochs of low masker energy in the fluctuating masker where the cues underlying binaural signal detection are more salient. The hypothesis was evaluated using the time-domain version of COSS analysis derived by Buus et al. [J. Acoust. Soc. Am.99, 2288–2297 (1996)] which measures the perceptual weight applied by a listener within a relatively brief time window as a function of the masker level during the window. The results indicated a dependency of signal detection on short-term masker level in the NoSπ condition but not in the NoSo condition. This finding supports a new perspective indicating that binaural signal detection depends upon the envelope of a masker in a way that is fundamentally different from that typically associated with monaural detection.

ISSN:0001-4966    

DOI:10.1121/1.422779

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

Megaderma lyra, a bat species using harmonically structured calls for echolocation, exploits the spectral content of its echoes for texture discrimination. It is the aim of the present study to test according to which sensory qualities harmonic complex tones are spontaneously classified by this bat. The applied experimental paradigm is especially adapted to the preference ofM. lyrato use absolute pitch cues. Three animals were trained in a 2-AFC procedure to classify three-component stimuli as low or high, with all their harmonics below or above a pure tone reference of 33 kHz, respectively. Later, the original tones were interspersed with “incomplete” test stimuli, with their fundamentals (and lower harmonics) missing. These were ambiguous in that their possible virtual, i.e., collective pitches were below the reference whereas their pure tone pitches were above it. Bat 1 classified 22 of 23 test stimuli with missing fundamentals between 5.3 and 28.3 kHz according to their collective pitches, whereas bat 2 judged all presented ambiguous tones on the basis of their pure tone pitches. Bat 3 failed the pitch control criterion which is why in this case results cannot be interpreted unequivocally. The implications of these findings are discussed with respect to the bats’ behavioral context, as well as to psychoacoustical models of the formation of the pitch of complex tones.

ISSN:0001-4966    

DOI:10.1121/1.422780

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

A harmonic of a periodic complex tone can be heard out as a separate entity if the harmonic is slightly mistuned from its correct frequency. Pitch matching experiments show that the pitch of such a mistuned harmonic differs systematically from its frequency. The shift in pitch is found to be an exaggeration of the frequency mistuning. This article considers two classes of model for the pitch shift. In the first class are tonotopically local interaction models which attribute the pitch shift to interactions between the mistuned harmonic and neighboring harmonics, where the neighborhood is established by peripheral filtering. The second class of model attributes the pitch shift to a contrast between the mistuned harmonic and a broadband harmonic template. This article describes six pitch matching experiments using complex tones having spectral gaps, strategically chosen to compare local interaction and template models. The results show that when a competition is set up between local interactions and a template, the template proves to be dominant. A parallel between the pitch shifts of mistuned harmonics and periodicity pitch, also attributed to a harmonic template, is seen as the frequency range of the mistuned harmonic is changed. Tonotopically local influences are evident in several experiments, but they are of secondary importance.

ISSN:0001-4966    

DOI:10.1121/1.422781

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

Research examining the discrimination of monaural phase change has suggested that temporal envelope shape, which varies with phase, may be an important cue. Much of that research employed stimuli consisting of three components, a center frequency(Fc),which is varied in phase, and an upper and lower sideband separated from the carrier by some frequency(ΔF).As the phase of the center component is varied, both temporal envelope and temporal fine structure change. The present research explored the salience of both envelope and fine structure as cues in a phase discrimination task. Monkeys were trained to report detection of a change from a three-tone complex with 90° starting phase for the center component to one in which the starting phase was smaller. In general, for the values ofFctested, thresholds for phase change decreased asΔFincreased. When tested with comparison stimuli that had a temporal envelope closely matched to that of the standard, but 0° starting phase, subjects had difficulty discriminating these stimuli from the standard for smallerΔF,but readily discriminated them at largerΔFvalues. These findings suggest that temporal envelope is a critical cue in discrimination of three-tone complexes on the basis of the starting phase of the center component at small values ofΔF,but that other cues are used at largerΔFvalues.

ISSN:0001-4966    

DOI:10.1121/1.422782

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

Lateralization and just-noticeable difference (jnd) measurements relative to the center were tested in a large group of patients with pontine lesions caused either by stroke or multiple sclerosis. Stimuli included binaural clicks, and low- and high-frequency narrow-band noise bursts. Two major types of abnormalities were revealed in the lateralization performances: perception of all stimuli, regardless of interaural differences (time and/or level) in thecenterof head (center-oriented), or lateralization of all stimuli to one side or the other of the head (side-oriented). The only significant correlation between jnd and lateralization performances was that an elevated jnd was always manifested in abnormal lateralization, while abnormality in lateralization did not necessarily indicate an abnormal jnd. Center-oriented lateralization was observed either for both interaural differences or only for one of them, and was found in both MS and stroke patients. All side-oriented stroke patients were similarly unable to center binaural stimuli for both time and level cues, whereas only one MS patient had this abnormality for interaural time differences, while his level performance was normal. More abnormalities were detected in the narrow band stimuli tests, although in some cases performance was more degraded for click stimuli. Lateralization tasks with high-frequency stimuli were more sensitive detectors of abnormality than jnd for any kind of stimulus, or lateralization tasks with low-frequency stimuli or clicks.

ISSN:0001-4966    

DOI:10.1121/1.422783

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

This paper describes the effect of spectro-temporal factors on human sound localization performance in two dimensions (2D). Subjects responded with saccadic eye movements to acoustic stimuli presented in the frontal hemisphere. Both the horizontal (azimuth) and vertical (elevation) stimulus location were varied randomly. Three types of stimuli were used, having different spectro-temporal patterns, but identically shaped broadband averaged power spectra: noise bursts, frequency-modulated tones, and trains of short noise bursts. In all subjects, the elevation components of the saccadic responses varied systematically with the different temporal parameters, whereas the azimuth response components remained equally accurate for all stimulus conditions. The data show that the auditory system does not calculate a final elevation estimate from a long-term (order 100 ms) integration of sensory input. Instead, the results suggest that the auditory system may apply a “multiple-look” strategy in which the final estimate is calculated from consecutive short-term (order few ms) estimates. These findings are incorporated in a conceptual model that accounts for the data and proposes a scheme for the temporal processing of spectral sensory information into a dynamic estimate of sound elevation.

ISSN:0001-4966    

DOI:10.1121/1.422784

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

The purpose of the study was to examine the acoustic, aerodynamic, physiologic, and perceptual characteristics of modal and vocal fry production. Twenty normal speakers (10 males, 10 females) participated in the study. Speech material included four sustained vowels (/i/, /ɑ/, /æ/, /u/), and syllable strings of /pi/ repetitions produced in both modal and vocal fry registers. Acoustic data (fundamental frequency, jitter, shimmer, and signal-to-noise ratio), aerodynamic data (airflow and air pressure), and electroglottographic (EGG) data were obtained simultaneously. Results demonstrated considerable differences across voice parameters for the modal and vocal fry registers. Fundamental frequency was significantly lower in vocal fry than in modal register for both males and females, however, significant gender differences existed only in modal register. For both males and females, measurements of jitter and shimmer were significantly higher and signal to noise ratio was significantly lower in vocal fry. In addition, airflow rate in modal register was almost three times as high as the airflow rate in vocal fry register during sustained vowel production. During syllable string production, subglottal air pressure values in modal register were approximately 1.5 times higher than that in the vocal fry register. In general, these data emphasize that the aeromechanical mechanisms of vocal fold vibratory behavior are substantially different between modal and vocal fry registers. A model of vocal fry phonation is presented to account for the present results.

ISSN:0001-4966    

DOI:10.1121/1.422785

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

The automatic parametrization of the first derivative of glottal flow is studied. Representatives of the two types of methods used most often for parametrization were tested and compared. The chosen representatives are all based on the Liljencrants–Fant model. As numerous tests were needed for a detailed comparison of the methods, a novel evaluation procedure is used which consists of the following stages: (1) use the Liljencrants–Fant model to generate synthetic flow pulses; (2) estimate voice source parameters for these synthetic flow pulses; and (3) calculate the errors by comparing the estimated values with the input values of the parameters. This evaluation procedure revealed that in order to reduce the average error in the estimated voice source parameters, the estimation methods should be able to estimate noninteger values of these parameters. The proposed evaluation method was also used to study the influence of low-pass filtering on the estimated voice source parameters. It turned out that low-pass filtering causes an error in all estimated voice source parameters. On average, the smallest errors were found for a parametrization method in which a voice source model is fitted to the flow derivative, and in which the voice source model is low-pass filtered with the same filter as the flow derivative.

ISSN:0001-4966    

DOI:10.1121/1.422786

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

This study examined the effect of sentence context and local acoustic structure on phoneme categorization. Target stimuli from a 10-step GOAT–COAT continuum, differing only on a temporal cue for voice onset time (VOT), were embedded in carrier sentences that biased interpretation toward either “goat” or “coat.” While subjects listened to the sentences they also responded as quickly as possible to a visual probe by indicating whether the probe matched the target stimulus they heard. Results showed that the interaction of VOT and sentence context significantly affected both identification and RT for stimuli near the perceptual boundary; the identification function showed a boundary shift in favor of the biased context and peak response times for each context reflected the shifted identification boundaries. In addition, response times were faster for identification of stimuli near the category boundary when responses were congruent, rather than incongruent with the sentence context. The response time differences for congruent versus incongruent responses in the boundary region are interpreted as depending on the results of initial phonological analysis; potentially ambiguous categorizations may be subject to additional evaluation in which a context-congruent response is both preferred and available earlier.

ISSN:0001-4966    

DOI:10.1121/1.422787

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

Factors leading to variability in auditory-visual (AV) speech recognition include the subject’s ability to extract auditory (A) and visual (V) signal-related cues, the integration of A and V cues, and the use of phonological, syntactic, and semantic context. In this study, measures of A, V, and AV recognition of medial consonants in isolated nonsense syllables and of words in sentences were obtained in a group of 29 hearing-impaired subjects. The test materials were presented in a background of speech-shaped noise at 0-dB signal-to-noise ratio. Most subjects achieved substantial AV benefit for both sets of materials relative to A-alone recognition performance. However, there was considerable variability in AV speech recognition both in terms of the overall recognition score achieved and in the amount of audiovisual gain. To account for this variability, consonant confusions were analyzed in terms of phonetic features to determine the degree of redundancy between A and V sources of information. In addition, a measure of integration ability was derived for each subject using recently developed models of AV integration. The results indicated that (1) AV feature reception was determined primarily by visual place cues and auditory voicing+manner cues, (2) the ability to integrate A and V consonant cues varied significantly across subjects, with better integrators achieving more AV benefit, and (3) significant intra-modality correlations were found between consonant measures and sentence measures, with AV consonant scores accounting for approximately 54% of the variability observed for AV sentence recognition. Integration modeling results suggested that speechreading and AV integration training could be useful for some individuals, potentially providing as much as 26% improvement in AV consonant recognition.

ISSN:0001-4966    

DOI:10.1121/1.422788

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP