摘要:

A method of single‐phase drive of an ultrasonic rotary motor is proposed where the vibration mode of a circular stator is rotated by a single‐phase source. If a small mass is attached to the circular ring vibrator, the degenerate doublets of the vibration mode are perturbed and separated into two orthogonal vibration modes with different resonance frequencies. The two modes can be excited with a phase difference of 90° by a single‐phase source if the amount of the mass is appropriate. This causes the rotation of the vibration mode. The proposed method is successfully studied theoretically and compared well experimentally.

ISSN:0001-4966    

DOI:10.1121/1.401703

出版商:Acoustical Society of America    

年代:1991

数据来源: AIP

摘要:

Symmetric and antisymmetric wave propagations in a pyroelectric plate of crystal class 2 are considered. The frequency equations are derived when the surfaces of the plate are traction free and completely coated with electrodes that are shorted and thermally insulated. The frequency equations are also deduced for crystal classes 2 mm and 6 mm. Numerical work has been carried out for piezoelectric polyvinylidene fluoride belonging to the 2‐mm class as heat conduction coefficients and specific heat capacity are small compared to other material constants of polyvinylidene fluoride. Barium titanate ceramic is considered for numerical calculation to illustrate the effect of pyroelectricity. Results are tabulated and the dispersion curves are also given.

ISSN:0001-4966    

DOI:10.1121/1.401652

出版商:Acoustical Society of America    

年代:1991

数据来源: AIP

摘要:

Wind tunnels are frequently used in the experimental study of moving sound sources. Although a number of techniques are currently used to determine the radiation characteristics of a sound source in a wind tunnel, they are usually limited by a lack of explicit directional information and/or a requirement that measurements be made in a free field. The multiple microphone acoustic intensity technique provides explicit directional information and can be used to measure sound fields in the near field of a source and, therefore, represents a possible alternative to the current measurement techniques used in wind tunnels. The formulations currently used to measure acoustic intensity are limited to either zero flow or plane waves in a one‐dimensional mean flow. A new formulation has been developed that extends the method to the case of a spherically spreading wave in a uniform one‐dimensional flow. Using an analytical simulation, the intensity distributions for a monopole and dipole source are studied. Initial results suggest that the formulation is suitable for the analysis of compact sources. Although a more detailed study will be required to develop a practical measurement tool, this study provides additional insight into the problem of intensity measurement in the presence of mean flow.

ISSN:0001-4966    

DOI:10.1121/1.401653

出版商:Acoustical Society of America    

年代:1991

数据来源: AIP

摘要:

Multiple scattering blurs the distinction between different material systems beyond a certain distance from the observation point, thereby rendering most random systems cloudy in appearance and opaque in the sense of structure delineation. However, based on a theoretical analysis, it will be shown that, due to the phase coherent nature of wave propagation through random media, some remnant information is still present which can be used to detect and locate new growing cracks. This offers the possibility to extend acoustic nondestructive evaluation techniques in the realm of highly heterogeneous media, such as composites or concrete analyzed by high‐frequency sound waves.

ISSN:0001-4966    

DOI:10.1121/1.401654

出版商:Acoustical Society of America    

年代:1991

数据来源: AIP

摘要:

An ultrasonic method to measure coagulation time for prothrombin time (PT) is discussed. This method is based on the measurement of ultrasonic scattering from spherical glass particles of 200‐μm diameter kept in motion, inside of a holder containing 0.1 ml of plasma, by ultrasonic energy. The incident wave (2.7 MHz) not only keeps the particle in motion but also is the source for the scattered waves. A receiving transducer captures part of the scattered wave and generates at its electrical output a signal containing amplitude and phase fluctuations. The motion of the particles are strongly influenced by the rheological changes during the process of coagulation. When the clot is formed, the amplitude of the motion of these particles is significantly reduced and so the fluctuations on the received signal stop. The time from the start of the coagulation process until the end of the fluctuations at the received signal is the coagulation time. Experimental results demonstrate that the ultrasonic method has precision and accuracy compatible to those provided by the manual tilt‐tube method when PT is measured with normal and abnormal samples of human plasma.

ISSN:0001-4966    

DOI:10.1121/1.401655

出版商:Acoustical Society of America    

年代:1991

数据来源: AIP

摘要:

A multiphonic is a regime of oscillation of woodwind musical instruments that is perceived as two or more simultaneously sounding pitches. The frequenciesfl,mof the line spectral components of a measured woodwind multiphonic tone fit a biperiodic spectrum at low‐ to mid‐playing levels. For the saxophone and clarinet multiphonics investigated, the two basis frequencies of the biperiodic spectrum are phase locked, that is, their ratio is equal to a ratio of small integers. A broadband spectrum is present in multiphonic spectra that exceeds instrumentation noise and window leakage associated with signal processing. The correlation dimensionDof P. Grassberger and I. Procaccia [Physica D9, 189–208 (1983)] is measured by embedding a single measured time series in a higher‐dimensional space, so as to reconstruct the phase space of the dynamical system. The time delay used in the dimensional reconstruction is chosen using information theory. For the particular multiphonics analyzed, the correlation dimension ranges from 2.5 to 2.9 for the saxophone and from 1.3 to 2.2 for the clarinet. One clarinet multiphonic shows possible additional dynamical complexity at small length scales in the embedding space, with a correlation dimension of 3.3. These results give quantitative evidence that some, but not all, multiphonic tones possess a strange attractor.

ISSN:0001-4966    

DOI:10.1121/1.401656

出版商:Acoustical Society of America    

年代:1991

数据来源: AIP

摘要:

In this paper, three experiments are reported that were run in order to assess the quality of Dutch synthetic speech using accented and unaccented diphones, i.e., diphones extracted from accented and unaccented syllables, respectively. In a paired‐comparison design, subjects were asked to evaluate the naturalness and fluency of different versions of an utterance. The results of the first two experiments, in which isolated polysyllabic words were used, indicate that the use of accented or unaccented diphones has a perceptual effect on phonologically long vowels only. In a third experiment, the use of the different diphone types in short sentences with a fixed temporal structure was evaluated. Results suggest that using unaccented diphones in unaccented or secondarily accented syllables does not result systematically in more natural‐sounding speech.

ISSN:0001-4966    

DOI:10.1121/1.401657

出版商:Acoustical Society of America    

年代:1991

数据来源: AIP

摘要:

A series of experiments compared two approaches to fricative identification, spectral template matching and articulatory dynamics. Natural‐speech /s/ and /1/ noises from fricative‐vowel or vowel‐fricative syllables were cross spliced so that ‘‘hybrid’’ noises started out as either /s/ or /1/ and ended up with the other fricative noise in varying proportions. With both initial and final fricatives, listener judgments most often agreed with the longer part of the noise even when spectral templates would predict the other category. Also, the vocalic formant transitions contributed to the judgment. In another experiment, open transcriptions by four expert listeners similarly showed that all the cues were used; there were also some instances of nonspeech percepts that would be predicted by gestural models. One further experiment had subjects identify two fricatives from hybrid noises between two vocalic segments. When the order of the noises differed from the order of the transitions, the perceived ordering of the fricatives was often the reverse of the order of the noise segments. Taken together with previous results, these experiments indicate that listeners take the whole fricative noise, as well as the transitions, into account in fricative identification.

ISSN:0001-4966    

DOI:10.1121/1.401658

出版商:Acoustical Society of America    

年代:1991

数据来源: AIP

摘要:

Identification accuracy and error patterns on the City University of New York (CUNY) Nonsense Syllable Test were examined for three groups of subjects (young normal‐hearing, older hearing‐impaired, and older with minimal hearing loss) listening binaurally in four conditions (quiet, noise, reverberation, and reverberation plus noise). Percent‐correct performance was analyzed for stimuli aggregated by place and manner categories, and error patterns were examined via analysis of variance and correlational procedures. Results suggested that some of the difficulty experienced by the older subjects was related to amount of hearing loss, but a portion of the data could not be explained by elevated auditory thresholds. Confusion patterns also varied across listening conditions, especially for the nasal and semivowel stimuli.

ISSN:0001-4966    

DOI:10.1121/1.401659

出版商:Acoustical Society of America    

年代:1991

数据来源: AIP

摘要:

The McGurk effect is a phenomenon that demonstrates a perceptual fusion between auditory and visual (lip‐read) information in speech perception under the condition of audio‐visual discrepancy, created by dubbed video tapes. This paper investigated whether or not the McGurk effect could be extended to Japanese subjects listening to Japanese syllables of different auditory intelligibility. The audio and video signal of a female talker’s speech for ten Japanese syllables (/ba/, /pa/, /ma/, /wa/, /da/, /ta/, /na/, /ra/, /ga/, /ka/) were combined on videotapes, giving 100 audio‐visual stimuli. These stimuli were presented to ten Japanese subjects who were required to identify the stimuli as heard speech in both noise‐added and noise‐free conditions. For both conditions, the intelligibility of the auditory stimuli was measured, by presenting the audio‐alone stimuli. The results showed that, in the noise‐free condition, the McGurk effect was small and almost limited to auditory stimuli of which the intelligibility was less than 100%. In the noise‐added condition, the McGurk effect was very strong and widespread. These results indicate that the ‘‘Japanese McGurk effect’’ is less easily induced than the English one, and that it depends on the auditory intelligibility of the speech signal.

ISSN:0001-4966    

DOI:10.1121/1.401660

出版商:Acoustical Society of America    

年代:1991

数据来源: AIP