摘要:

Nonlinear interaction of ultrasonic waves is discussed from the very general quantum mechanical viewpoint. By using the concept of three‐phonon interactions one is able to derive formulae for power and intensity of ultrasonic waves generated through nonlinear mixing of two ultrasonic waves, as well as the formula for parametric amplification of an ultrasonic wave through its nonlinear interaction with another ultrasonic wave. The effect of attenuation on nonlinear ultrasonic wave interactions also is discussed, and it is shown that in some situations attenuation strongly affects the generation of the second harmonic of an initially sinusoidal ultrasonic wave. It is shown that in the correspondence limit, the quantum mechanical viewpoint gives results which are in very good agreement with results obtained from classical physics.

ISSN:0001-4966    

DOI:10.1121/1.385115

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

We have explored some musical effects of tones with nonharmonic partials. The spacing of partials can be stretched so that each partial frequencyfijpresent in tones sounded singly or together is given byfij=Ai/12+log2j. Hereiis the scale step in semitones,jis the partial number, andAis the frequency ratio of a pseudo‐octave (A=2 for a true octave). We find that subjects can match the keys of stretched (A=2.4) as well as unstretched passages. Stretched cadences (A=2.4) do not seem final. But, a stretched ’’cadence’’ with equally spaced partials that goes from closely spaced (tonally dissonant) to widely spaced (tonally consonant) partials does seem final. Our experiments do not decide finally among three views of harmony: that harmony depends on a fundamental bass or periodicity pitch (Rameau), that harmony depends on the spacing of partials (Helmholtz and Plomp) or that harmony is a matter of brainwashing.

ISSN:0001-4966    

DOI:10.1121/1.385116

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

Dichotic CV recognition at interaural temporal onset asynchronies (lag times) of 0, 30, 60, and 90 ms was investigated in normal hearing young and elderly subjects. The results for the young group were consistent with those reported in previous studies (Studdert‐Kennedyetal., 1970; Berlinetal., 1973a). The older group demonstrated a mean right ear advantage (REA) at simultaneity of 12.7%, which was not significantly different from that of the young group (12.4%). This suggests that the processes subserving the REA are not affected by age. However, there was a significant reduction in the total (right ear plus left ear) dichotic scores of the elderly group compared to the young; suggesting an age‐associated reduction in the channel capacity of the aging auditory system. Further, there were striking aberrations of the dichotic lag effect in the elderly group compared to the young subjects, consistent with age‐related changes in auditory temporal processing. The findings are discussed with respect to the aging auditory system and the nature of dichotic speech processing.

ISSN:0001-4966    

DOI:10.1121/1.385117

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

The purpose of this study was to investigate acoustic attributes of the voices of preadolescent children as a function of sex and age. Voice samples of the sustained vowel /a/ were obtained from 180 children, 15 males and 15 females at ages five, six, seven, eight, nine, and ten years. Measurement of fundamental frequency was obtained to determine sex‐related differences and age‐related trends. This acoustic analysis revealed that a male/female difference in fundamental frequency emerged by age seven, and that fundamental frequency decreased significantly in male children only, between age five and age ten.

ISSN:0001-4966    

DOI:10.1121/1.385118

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

The purpose of this study was to investigate the perception of transformations by varying the voice onset time (VOT) of the repeating stimulus, its repetition number, and intensity level. Fifteen subjects rated the 5‐, 25‐, and 55‐ms VOT stimuli during periods of repetitions so that transformations could be identified according to their place and voicing characteristics. The number of stimulus repetitions was 5, 32, or 95, and the sound‐pressure level of the repeating stimulus was 50, 70, or 90 dB. The major findings were as follows: (1) The 90‐dB level condition produced significantly more transformations than either the 50‐ or 70‐dB conditions for the 55‐ms stimulus only; (2) A significant difference in number of transformations was obtained for each paired comparison of the 55‐ms stimulus, but only between the 5‐and the 32‐ and 95‐ repetitions pairs for the 5 and 25 ms stimuli; and (3) Significant correlations were obtained between the voiceless and alveolar features of transformations for the 55‐ms stimulus, and between the voiced and alveolar and velar features of transformations for the 5‐ and 25‐ms stimuli. The findings support a transformation process sensitive to voicing and place cues and a peripheral component of transformations.

ISSN:0001-4966    

DOI:10.1121/1.385119

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

One of the most important operations in isolated word speech recognition systems is the method used to obtain the word reference templates. For speaker trained systems, the techniques that have been used include casual training, averaging, and use of statistical pattern recognition clustering methods. In a recent study, Rabiner and Wilpon showed that the statistical techniques, when combined with the technique of averaging the autocorrelation coefficients of all tokens within the cluster, provided a reliable, robust set of reference templates. The only drawback to this method was the extensive, burdensome training required for the statistical analysis. Since the statistical training method could not be used in most practical situations, techniques were investigated for obtaining a simplified, robust training procedure which would incorporate many of the ideas of the statistical approach. Such a training method is described in this paper. The advantages of this new training procedure, over (previously used) casual training include: ease of use, robustness of the templates, minimized computation in the recognition algorithm, normalized durations of all references, and recognition accuracy comparable to previous systems with double the number of templates.

ISSN:0001-4966    

DOI:10.1121/1.385120

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

This paper reports four whole‐body vibration experiments conducted to determine the effects of ’’pulse’’ duration and combinations of ’’pulses’’ of vibration on human discomfort. The first experiment investigated the variation in discomfort with vibration duration for the frequencies 4, 8, 16, and 32 Hz and durations from one cycle of motion to 4 s. The second experiment extended the results for 8‐Hz vibration to durations up to 32 s. The third experiment involved complex motions with one predominant frequency and root mean square acceleration level but differing peak levels. The final experiment investigated the effect of vibration duration at different vibration frequencies. The results of the first two experiments conflict with previous reports of a short finite integration time for human response to vibration. The data are used to devise a procedure for predicting the discomfort of the motions used in the third experiment. The procedure which is based on a ’’root‐mean‐quad’’ unit: rmq=[T−1FT0a4(t) dt]1/4indicates that motions of the same frequency and same rms level will cause greater discomfort with increasing peak levels. The predictions are in good general agreement with the experimental results. Possible uses of the rmq unit are discussed.

ISSN:0001-4966    

DOI:10.1121/1.385121

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

A baseline‐probe technique was used to investigate target echo recognition by an echolocating Atlantic bottlenose porpoise (Tursiopstruncatus). Baseline performance was established using a two‐alternative, forced‐choice method, with two hollow aluminum and two coral rock cylinders (standard targets) presented successively in a random sequence. After a near errorless performance was achieved with the standard targets, probe targets were used to investigate the animal’s target echo recognition capability. The probe target results suggested that the animal learned to recognize the characteristics of echoes from the aluminum standards and differentiated other targets on that basis. All of the targets were subsequently examined by using a broadband porpoise‐like acoustic signal. Analysis of the echoes suggested a strong correlation between the behavioral results and measured characteristics of the envelopes of the matched filter responses to the echoes.

ISSN:0001-4966    

DOI:10.1121/1.385015

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

This paper is a sequel to a study which showed that the dominant dimension for perceptual discrimination among normal voices was the male–female categorization and which also suggested that discrimination within the male–female categories utilized distinct dimensions. The present study eliminates the male–female axis by treating the gender groups separately and making the within‐category dimensions available for more sensitive analysis. The purpose was to determine the number and nature of perceptual parameters needed to explain judgments of voice similarity depending on talker sex and whether the stimulus sample was a sustained vowel or a short phrase. The similarity judgments were submitted to multidimensional analysis via INDSCAL and the resulting dimensions were interpreted in terms of available acoustic measures and unidimensional voice‐quality ratings of pitch, breathiness, hoarseness, nasality, and effort. The decisions of the listeners appeared to be influenced by both the sex of the speaker and the stimulus sample, although fundamental frequency (f0), was important for all judgments. Aside from thef0dimensions, judgments concerning male voices were related to vocal tract parameters, while similarity judgments of female voices were related to perceived glottal/vocal tract differences. Formant structure was apparently important in judging the similarity of vowels for both sexes while perceptual glottal/temporal attributes may have been used as cues in the judgments of phrases.

ISSN:0001-4966    

DOI:10.1121/1.385122

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

A noise mixed with its repetition after a delay oftsec can produce a pitch corresponding to 1/t. The accepted range of this echo pitch is about 50 through 2000 Hz (tfrom 0.02 through 5×10−4sec). Evidence is presented suggesting that temporal analysis should permit detection of echo repetition well below the pitch limit oft=0.02 sec. In keeping with predictions, we found that listeners could detect the delay of echo repetition for noise down to at leastt=0.5 sec (periodicity of 2 Hz). While polarity inversion of the echo alters apparent frequency at delays producing pitch, such inversion has no effect on apparent frequency of infrapitch echo. It is suggested that echo detection within the pitch range involves both a neural place analysis of the rippled power spectrum and a concurrent neural temporal analysis insensitive to polarity inversion; echo detection in the infrapitch range cannot employ neural place cues and is based solely upon a polarity‐insensitive temporal analysis. Infrapitch repetition is discussed as a tool for investigating temporal domain analysis free from concurrent frequency domain analysis.

ISSN:0001-4966    

DOI:10.1121/1.385096

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP