摘要:

Although a psychometric function describing a subject’s responses to some physical stimuli is of considerable value, characterizing such functions is time consuming and, hence, is not carried out routinely in psychophysical experiments. A principal reason for the lack of efficiency in characterizing a psychometric function is the use of sampling methods that either converge on a single point on the psychometric function, such as the PEST method, or which distribute observations uniformly over a wide range, such as the constant stimuli method. As an alternative, a multimodal four-point sampling method has been proposed [C. F. Lam, J. H. Mills, and J. R. Dubno, J. Acoust. Soc. Am.99, 3689–3693 (1996)]. A psychometric function is then fitted to the four points (each with several trials) to estimate the threshold and slope parameters of the psychometric function. Adaptive methods, such as the up–down methods [H. Levitt, J. Acoust. Soc. Am.49, 467–477 (1971)], can be used to provide good initial estimates of the threshold and spread parameters of a psychometric function described by a logistic function. In ongoing studies of age-related changes in auditory masking and discrimination, this new four-point sampling method has been applied to determine psychometric functions for absolute thresholds as a function of duration, thresholds in simultaneous and forward masking, frequency discrimination, and intensity discrimination in both young and aged human subjects. Results indicate that a reduction in data collection time of about 50% with no increase in variance can be achieved. This increase in efficiency applies to simple detection tasks by normal hearing subjects as well as to complex discrimination tasks by older subjects with hearing loss.

ISSN:0001-4966    

DOI:10.1121/1.420155

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

A lexical modeling methodology was employed to examine how the distribution of phonemic patterns in the lexicon constrains lexical equivalence under conditions of reduced phonetic distinctiveness experienced by speechreaders. The technique involved (1) selection of a phonemically transcribed machine-readable lexical database, (2) definition of transcription rules based on measures of phonetic similarity, (3) application of the transcription rules to a lexical database and formation of lexical equivalence classes, and (4) computation of three metrics to examine the transcribed lexicon. The metric percent words unique demonstrated that the distribution of words in the language substantially preserves lexical uniqueness across a wide range in the number of potentially available phonemic distinctions. Expected class size demonstrated that if at least 12 phonemic equivalence classes were available, any given word would be highly similar to only a few other words. Percent information extracted (PIE) [D. Carter, Comput. Speech Lang.2, 1–11 (1987)] provided evidence that high-frequency words tend not to reside in the same lexical equivalence classes as other high-frequency words. The steepness of the functions obtained for each metric shows that small increments in the number of visually perceptible phonemic distinctions can result in substantial changes in lexical uniqueness.

ISSN:0001-4966    

DOI:10.1121/1.420402

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

Recent research on 5- to 11-year-old children’s perception of stop consonants and vowels indicates that they can generally identify these sounds with relatively high accuracy from short duration stimulus onsets [Ohde et al., J. Acoust. Soc. Am.97, 3800–3812 (1995); Ohde et al., J. Acoust. Soc. Am.100, 3813–3824 (1996)]. The purpose of the current experiments was to determine if younger children, aged 3–4 years, can also recover consonant and vowel features from stimulus onsets. Ten adults, ten 3-year olds, and ten 4-year-olds listened to synthesized syllables composed of combinations of [b d g]and [i u ɑ]. The synthesis parameters included manipulations of the following stimulus variables: formant transition (moving or straight), noise burst (present or absent), and voicing duration (10, 30, or 46 ms). Developmental effects were found for the perception of both stop consonants and vowels. In general, adults identified these sounds at a significantly higher level than children, and perception by 4-year-olds was significantly better than 3-year-olds. A developmental effect of dynamic formant motion was obtained, but it was limited to only the [g]stop consonant. Stimulus duration affected the children’s perception of vowels indicating that they may utilize additional auditory information to a much greater extent than adults. The results support the importance of information in stimulus onsets for syllable identification, and developmental changes in sensitivity to these cues for consonant and vowel perception.

ISSN:0001-4966    

DOI:10.1121/1.420135

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

Previous studies of infant cry acoustics and their perceptual significance have remained inconclusive as to the graded nature of cry production and perception and to the exact role and importance of particular acoustic features. In this study, a set of infant cries were digitally analyzed and resynthesized to form natural-sounding cries with varying fundamental frequency(F0),degrees of jitter (period to period variations inF0), and rise time (time forF0to reach its maximum value). In a perceptual rating task, higher-F0cries as well as cries with larger amounts of jitter tended to be given more negative ratings than were lower-F0cries and cries with less jitter, respectively. The perceptual ratings of the rise time manipulations were inconclusive. This study demonstrated a perceptual effect ofF0and jitter independently of other parameters, consistent with current notions of infant cry gradedness. It was also shown that digital signal processing techniques can be fruitfully applied to infant cry research.

ISSN:0001-4966    

DOI:10.1121/1.420403

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

Does the newborn’s well-known sensitivity to human speech include awareness of the distinction between strong and weak syllables, as has been shown for older infants and adults? The non-nutritive high-amplitude sucking paradigm was used to investigate whether weak syllables play a role in neonate perceptual representation. Two-day-old French infants were tested on their capacity to discriminate phonetically highly varied words containing syllables with various strong vowels versus the weak, reduced vowel schwa in natural, isolated English words. Twenty infants heard lists of weak–strong and lists of strong words (e.g.,belief, control,etc. versusnose, dream, etc.) and 20 heard lists of weak–strong and strong–strong words (e.g.,belief, control, etc. versusvolume, rhubarb, etc.). The results show that weak–strong words were reliably distinguished from strong words, but not from strong–strong words. Taken together, the findings indicate that a weak, reduced vowel is equivalent to a strong, full vowel to the extent that both count as syllabic nuclei. Moreover, this global equivalence in terms of number of syllabic constituents apparently overrules the more local acoustic difference between strong and weak vowels. The role of syllabic/vocalic information in neonate representation is discussed.

ISSN:0001-4966    

DOI:10.1121/1.420136

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

Previous research has shown that young infants easily discriminate both native and non-native consonant contrasts, but by 10–12 months of age infants perform like adults and easily discriminate only native consonant contrasts. The present study was designed to determine what kind of experience is required to maintain discrimination of native consonants. To address this question, English listeners of three ages (6–8 months, 10–12 months, and adults) were presented with the phonetic difference, [d̥a] vs[t=a].This distinction occurs in English but is not phonemic:[t=a]occurs when it follows an [s] (as in /sta/). If passive exposure is sufficient to maintain discrimination, all age groups should discriminate [d̥a]vs[t=a].However, if phonological status plays a role, then older infants and adults should fail. In experiment 1, English adults judged [d̥a] and[t=a]to be equally good instances of the same phonemic category /da/. In an AX procedure in experiment 2, English adults discriminated [d̥a] vs[t=a]better than chance but worse than native phonemic levels. In the Conditioned Head Turn procedure in experiment 3, adults and 6- to 8-month-old infants discriminated [d̥a] vs[t=a],but 10- to 12-month-old infants did not. Taken together, these results are most consistent with the hypothesis that phonological status plays a role in maintaining discrimination of phonetic information.

ISSN:0001-4966    

DOI:10.1121/1.420137

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

The ability of listeners to estimate articulation scores for lists of nonsense syllables was evaluated. Normal-hearing subjects were presented with lists of from 50 to 60 nonsense syllables that were degraded with various amounts of noise or filtering and were instructed to estimate consonant-correct scores for each condition. To provide a reference for estimating, subjects were shown the accurate orthographic representation of the syllable on a computer monitor to compare with the auditory presentation. The printed version was displayed either simultaneously with the auditory presentation or 500 ms after the offset of the syllable. Estimates were collected on two occasions to examine test–retest reliability, and actual percent-correct scores were obtained to check the accuracy of the estimates. Most subjects overestimated actual scores when the printed representation was provided simultaneously, but estimates were strikingly similar to actual scores when the printed representation was delayed. The delay appeared to prevent the printed representation from favorably biasing the reception of the syllable. The average of two or three estimates gave highly repeatable results for both visual displays. Crossover frequencies derived from the filtered-speech conditions were within the range reported in the literature. This supports the conclusion that subjects based their estimates on the recognition of speech sounds rather than other percepts associated with the speech-in-noise conditions such as loudness of the noise. The estimation procedure permits the collection of articulation scores in much less time than required by traditional test procedures.

ISSN:0001-4966    

DOI:10.1121/1.420138

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

Behavioral perceptual abilities and neurophysiologic changes observed after listening training can generalize to other stimuli not used in the training paradigm, thereby demonstrating behavioral “transfer of learning” and plasticity in underlying physiologic processes. Nine normal-hearing monolingual English-speaking adults were trained to identify a prevoiced labial stop sound (one that is not used phonemically in the English language). After training, the subjects were asked to discriminate and identify a prevoiced alveolar stop. Mismatch negativity cortical evoked responses (MMN) were recorded to both labial and alveolar stimuli before and after training. Behavioral performance and MMNs also were evaluated in an age-matched control group that did not receive training. Listening training improved the experimental group’s ability to discriminate and identify an unfamiliar VOT contrast. That enhanced ability transferred from one place of articulation (labial) to another (alveolar). The behavioral training effects were reflected in the MMN, which showed an increase in duration and area when elicited by the training stimuli as well as a decrease in onset latency when elicited by the transfer stimuli. Interestingly, changes in the MMN were largest over the left hemisphere. The results demonstrate that training can generalize to listening situations beyond those used in training sessions, and that the preattentive central neurophysiology underlying perceptual learning are altered through auditory training.

ISSN:0001-4966    

DOI:10.1121/1.420139

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

The acoustic propagation properties of egg yolk and albumen are characterized in the frequency range 20–400 MHz by the bioultrasonic spectroscopy system using an ultrasonic transmission comparison method. Significant differences in the attenuation, velocity, impedance, and density among yolk and thick and outer thin albumen are observed. The acoustic properties of 10% aqueous solutions of ovalbumin and bovine hemoglobin are also measured in order to investigate the contribution of proteins to the acoustic properties of albumen. The differences obtained between thick and outer thin albumen may be mainly due to their macromolecular level structural differences, as their constituents are nearly the same.

ISSN:0001-4966    

DOI:10.1121/1.420404

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

Ultrasonic absorption coefficients were measured in aqueous solutions of imidazole and pyrazole by pulse and resonance methods in the frequency range from 3 to 220 MHz at 25 °C. Excess absorption was observed in both solutions. From the concentration dependence of the ultrasonic relaxation parameters associated with a single relaxational process in the solution of imidazole, the cause of the relaxation was proven to be due to a proton transfer reaction and the rate and equilibrium constants were determined for the process. The association rate constant for the ions was reasonable as a diffusion controlled reaction, although it is considerably greater than those in other amine solutions. A standard volume change of the reaction was also determined from the reactant concentration dependence of a maximum absorption per wavelength. The diffusion controlled rate constant for imidazole was considered in relation to the unique molecular structure of imidazole and the effect of the solute on water structure. In the solution of pyrazole, it was not possible to determine the relaxational parameters because the relaxation frequency was located quite below the measurement frequency range.

ISSN:0001-4966    

DOI:10.1121/1.420140

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP