摘要:

Sound localization ability has traditionally been studied using either a relative localization task, where thresholds to determine a difference in sound source location is approximately 1–10 degrees, or an absolute localization task, where the range of estimates of the source of a sound are 4–30 degrees. In order to directly relate these two psychophysical methods, we compared the psychometric functions from a relative localization task in a human subject to the same subject’s performance on an absolute localization task using three different acoustic stimuli: Gaussian noise, 1-kHz tones, and 4-kHz tones. The results showed that the relative localization threshold was a poor indicator of the range of estimates of the same stimulus in absolute space, however, the width of the relative localization psychometric functions was well correlated with the width of the distribution of estimates made in the absolute localization task. It is concluded that the relative localization psychometric functions, but not threshold, provides a reliable estimate of absolute spatial localization ability in human subjects, and suggested that the same neuronal mechanisms can underlie the psychophysical data using both methods.

ISSN:0001-4966    

DOI:10.1121/1.421222

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

The effect of adjusting the consonant–vowel (C–V) intensity ratio on consonant recognition in 18 subjects with sensorineural hearing impairment was investigated. C–V intensity ratios in a set of 48 vowel–consonant nonsense syllables were adjusted in steps of 3–6 dB depending on the subject’s dynamic range of hearing. An increase in consonant intensity is referred to here as consonant enhancement (CE). The value of CE producing the highest consonant recognition score (CRmax) is defined as CEmax. Both CEmax and CRmax were determined for each subject for each of the 48 nonsense syllables. Consonant type was found to have a highly significant effect on CRmax, the gain in consonant recognition, and CEmax. The effect of vowel environment was also significant, but of much smaller magnitude. Audiogram configuration was found to have a small effect and was only significant for CRmax. The results of the study also showed that individualized adjustment of the C–V intensity ratio for each subject and consonant–vowel combination can produce substantial improvements in consonant recognition. These data can be used to estimate upper bounds of performance that, in principle, can be obtained by appropriate adjustment of the C–V intensity ratio.

ISSN:0001-4966    

DOI:10.1121/1.423108

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

Facet surfaces of the cricoarytenoid joints from two cadaver larynges were digitized. The data were used to compute the optimal axis of rotation for each of the joints in the sense that the computed axis minimized the variance of the joint gap over the full range of joint motion. The optimal axis corresponded to a rocking motion of the arytenoid on the corresponding cricoid. This motion was consistent with experimental data from digitized recordings of vocal fold movement. Using the rigid laryngoscopic view, a similarity in vocal process movement, over the range in motion, between the rocking axis and the vertical axis described in the literature was found, resolving the controversy between two conflicting views of motion of the vocal processes.

ISSN:0001-4966    

DOI:10.1121/1.421223

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

Two experiments were conducted to examine the relationship between audibility and speech recognition for individuals with sensorineural hearing losses ranging from mild to profound degrees. Speech scores measured using filtered sentences were compared to predictions based on the Speech Intelligibility Index (SII). The SII greatly overpredicted performance at high sensation levels, and for many listeners, it underpredicted performance at low sensation levels. To improve predictive accuracy, the SII needed to be modified. Scaling the index by a multiplicative proficiency factor was found to be inappropriate, and alternative modifications were explored. The data were best fitted using a method that combined the standard level distortion factor (which accounted for decrease in speech intelligibility at high presentation levels based on measurements of normal-hearing people) with individual frequency-dependent proficiency. This method was evaluated using broadband sentences and nonsense syllables tests. Results indicate that audibility cannot adequately explain speech recognition of many hearing-impaired listeners. Considerable variations from audibility-based predictions remained, especially for people with severe losses listening at high sensation levels. The data suggest that, contrary to the basis of the SII, information contained in each frequency band is not strictly additive. The data also suggest that for people with severe or profound losses at the high frequencies, amplification should only achieve a low or zero sensation level at this region, contrary to the implications of the unmodified SII.

ISSN:0001-4966    

DOI:10.1121/1.421224

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

Five patients who used a six-channel, continuous interleaved sampling (CIS) cochlear implant were presented vowels, in two experiments, from a large sample of men, women, boys, and girls for identification. At issue in the first experiment was whether vowels from one speaker group, i.e., men, were more identifiable than vowels from other speaker groups. At issue in the second experiment was the role of the fifth and sixth channels in the identification of vowels from the different speaker groups. It was found in experiment 1 that (i) the vowels produced by men were easier to identify than vowels produced by any of the other speaker groups, (ii) vowels from women and boys were more difficult to identify than vowels from men but less difficult than vowels from girls, and (iii) vowels from girls were more difficult to identify than vowels from all other groups. In experiment 2 removal of channels 5 and 6 from the processor impaired the identification of vowels produced by women, boys and girls but did not impair the identification of vowels produced by men. The results of experiment 1 demonstrate that scores on tests of vowels produced by men overestimate the ability of patients to recognize vowels in the broader context of multi-talker communication. The results of experiment 2 demonstrate that channels 5 and 6 become more important for vowel recognition as the second formants of the speakers increase in frequency.

ISSN:0001-4966    

DOI:10.1121/1.421248

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

When two vowels are presented simultaneously, listeners can report their phonemic identities more accurately if their fundamental frequencies (F0’s) are different rather than the same. If theF0difference(ΔF0)is large, listeners hear two vowels on different pitches; if theΔF0is small the vowels are identified less accurately and they do not evoke different pitches. The present study used a matching task to obtain judgments of the pitches evoked by “double vowels” created from pairwise combinations of steady-state synthetic vowels /i/, /ɑ/, /u/, /æ/, and /ɚ/. OneF0was always 100 Hz; the otherF0was either 0, 0.25, 0.5, 1, 2, or 4 semitones higher. Experienced listeners adjusted theF0of a tone complex to assign pitch matches to 50-ms or 200-ms double vowels. ForΔF0’s up to two semitones, listeners’ matches formed a single cluster in the frequency region spanned by the twoF0’s. When theΔF0was 4 semitones, the matches generally formed two clusters close to theF0of each vowel, suggesting that listeners perceive two distinct pitches when theΔF0is 4 semitones but only one clear pitch (possibly accompanied by one or more weaker pitches) with smallerΔF0’s. When the duration was reduced from 200 ms to 50 ms, only a subset of the vowel pairs with aΔF0of 4 semitones produced a bimodal distribution of matches. In general, 50-ms stimuli were matched less consistently than their 200-ms counterparts, indicating that the pitches of concurrent vowels emerge less clearly when the stimuli are brief. Comparisons of pitch and vowel identification data revealed a moderate correlation between match intervals (defined as the absolute frequency difference between first and second pitch matches) and identification accuracy for the 200-ms stimuli with the largestΔF0of 4 semitones. The link between match intervals and vowel identification was weak or absent in conditions where the stimuli evoked only one pitch.

ISSN:0001-4966    

DOI:10.1121/1.421249

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

Japanese and Korean listeners’ identification and discrimination of English /r/ and /l/ were compared using a common set of minimal pair stimuli. The effects of speakers (two native speakers of Australian English), position of the contrast within the word (word initial, initial consonant cluster, and medial positions), and listening task (forced choice identification versus oddball discrimination) were examined, with a view to assessing the relative importance of language-specific and language-independent factors operating at the acoustic–phonetic and phonological levels of signal processing in “foreign sound” speech perception. Both prior phonological learning and the relative acoustic discriminability of the items affected subjects’ performance on the identification test. Where both factors were engaged, phonological learning effects predominated over the effects of acoustic discriminability. The extent to which a speaker encoded critical acoustic cues for the /r–l/ distinction was found to affect /r–l/ identification. Dynamic spectral features known to be relevant for the /r–l/ contrast were effective in predicting (in a linear regression analysis) speaker-dependent differences in identification scores. Although the discrimination test may have been influenced by ceiling effects, the performance profiles on the identification and discrimination tests were quite different, indicating that the identification and discrimination tests imposed quite different task demands upon listeners and that phonological processing of the signal was more engaged by the former task.

ISSN:0001-4966    

DOI:10.1121/1.421225

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

The time series of the segments from a Korean traditional song “Gwansanyungma” and a western song “La Mamma Morta” were investigated using chaotic analysis techniques. It is found that the phase portrait in the reconstructed state space of the time series of the segment from the Korean traditional song has a more complex structure in comparison with the segment from the western songs. The segment from the Korean traditional song has the correlation dimension 4.4 and two positive Lyapunov exponents which show that the dynamic related to the Korean traditional song is a high-dimensional hyperchaotic process. On the other hand, the segment from the western song with only one positive Lyapunov exponent and the correlation dimension 2.5 exhibits low-dimensional chaotic behavior.

ISSN:0001-4966    

DOI:10.1121/1.421226

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

Cultured Chinese hamster ovary cells attached to thin Mylar sheets were exposed to 3.3-MHz ultrasound in the presence ofAlbunex®ultrasound contrast agent. The ultrasound beam was directed upward at the exposure chamber with the monolayer on the inside of the upper acoustic window. Cell membrane damage was detected by the firefly enzyme assay for released ATP and the subharmonic, fundamental, and second harmonic scattered signals were recorded. ATP release increased monotonically with increasing pressure amplitude above apparent thresholds of 0.28 MPa for 1-s continuous and 0.56 MPa for 100-s pulsed (10-μs pulses, 1-ms PRP) exposures with 5%Albunex®.The subharmonic signal and, to a lesser extent, the second harmonic signal both increased with the cell membrane damage, which suggests that these signals have predictive value for bioeffects. If the monolayer was positioned on the front window of the exposure chamber, cell membrane damage was greatly reduced, which confirms the protective influence of this configuration of monolayers reported in the literature. The effect decreased both at high (50%) or low (0.5%) concentrations ofAlbunex®.The strong nonlinear scattering of ultrasound by contrast agent gas bodies appears to provide useful indicators of gas body activity including cavitational bioeffects.

ISSN:0001-4966    

DOI:10.1121/1.421250

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

Call production in budgerigars was studied using operant conditioning. In several experiments, budgerigars were reinforced with food for producing calls that were above or below a criterion level of intensity. This differential reinforcement procedure was successful in controlling vocal intensity in both directions showing that the intensity with which budgerigars produce vocalizations is under voluntary control. In additional experiments, call intensity maintained by food reinforcement was measured both in the quiet and in the presence of various levels of broadband noise. Call intensity in budgerigars increased significantly in noise, paralleling the well-known Lombard effect in humans which is the reflexive increase in speech intensity during communication in noise. Call intensity was measured in broadband noise and in a notched noise (no energy between 1.5 and 4.5 kHz) with the same overall level. Results show that noise in the spectral region of contact calls is most effective in causing an increase in vocal intensity. In aggregate, these experiments show that budgerigars have voluntary control over the intensive aspect of their vocalizations, that they normally monitor their vocal output though external auditory feedback, and, like humans, they exhibit the Lombard effect.

ISSN:0001-4966    

DOI:10.1121/1.421227

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP