摘要:

A voltage sensor using a Lamb wave delay line oscillator is described. The device consists of two pairs of interdigital transducers and one plate electrode at the central part of the device. All of these transducers have the counter electrodes on the bottom surface of the substrate. The oscillation frequency of the device changes significantly with the voltage applied to the central plate electrode. Performances of the voltage sensor are given, including sensitivity and its frequency dependence.

ISSN:0001-4966    

DOI:10.1121/1.389851

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

A foil electret microphone for use under the cuff of an automatic blood pressure monitoring system is described. The transducer is designed to operate with relatively flat sensitivity over a static pressure range of 40 to 250 mm Hg (5.33×104to 3.33×105dyn/cm2). The new electret microphone differs from conventional microphones used for airborne sound reception in two ways: (1) the diaphragm thickness is 50  μm rather than the typical 12.5 or 25  μm, and (2) the backplate contains a set of annular ridges spaced at 4 mm rather than the typical 7–10 mm. This microphone offers three advantages over the piezoelectric microphone now in use: (1) greater tolerance in positioning the microphone over the brachial artery, (2) nearly 20‐dB higher sensitivity and signal‐to‐noise ratio, and (3) the ability to obtain measurements with the microphone placed midway between the elbow and shoulder. Tests of the new foil electret microphone in conjunction with the automatic blood pressure monitoring system indicate that the automatic and conventional measurements of systolic and diastolic blood pressure agree to within 5 mm Hg at least 90% of the time. In addition, the electret microphone is able to obtain automatic measurements on subjects with a wider range of ages and sizes.

ISSN:0001-4966    

DOI:10.1121/1.389852

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

The effect of interposing a half‐wavelength membrane between the transducer and the load in mechanically sectored ultrasonic scanners was investigated. In particular, the effects of impedance mismatch and detuning on broadband spectra were theoretically and experimentally studied. These studies indicate that for certain common cases, a bandwidth reduction of 20%–30% can be anticipated, resulting in a proportional decrease in the axial resolution.

ISSN:0001-4966    

DOI:10.1121/1.389853

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

This investigation utilized a reflectionless tube technique to obtain direct estimates of turbulent noise produced at the glottis during whispered vowels. In the past, the glottal turbulent noise source has been described theoretically as a series pressure source having a spectrum that is relatively flat for 2 or 3 oct around a center frequency [K. N. Stevens, J. Acoust. Soc Am.50, 1180–1192 (1971)]. Center frequency is determined primarily by the area of the constriction at which turbulence is produced with the volume velocity of air flowing through the constriction. The present results were shown to substantiate this theoretically based description of the glottal turbulent noise source. In addition, there wasnosignificant difference between the glottal turbulent noise spectra of male and female speakers. The application of these findings to the synthesis of whispered vowels is discussed.

ISSN:0001-4966    

DOI:10.1121/1.389854

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

An adequate theory of vowel perception must account for perceptual constancy over variations in the acoustic structure of coarticulated vowels contributed by speakers, speaking rate, and consonantal context. We modified recorded consonant–vowel–consonant syllables electronically to investigate the perceptual efficacy of three types of acoustic information for vowel identification: (1) static spectral ‘‘targets,’’ (2) duration of syllabic nuclei, and (3) formant transitions into and out of the vowel nucleus. Vowels in /b/–vowel–/b/ syllables spoken by one adult male (experiment 1) and by two females and two males (experiment 2) served as the corpus, and seven modified syllable conditions were generated in which different parts of the digitized waveforms of the syllables were deleted and the temporal relationships of the remaining parts were manipulated. Results of identification tests by untrained listeners indicated that dynamic spectral information, contained in initial and final transitions taken together, was sufficient for accurate identification of vowels even when vowel nuclei were attenuated to silence. Furthermore, the dynamic spectral information appeared to be efficacious even when durational parameters specifying intrinsic vowel length were eliminated.

ISSN:0001-4966    

DOI:10.1121/1.389855

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

We have examined the effects of the relative amplitude of the release burst on perception of the place of articulation of utterance‐initial voiceless and voiced stop consonants. The amplitude of the burst, which occurs within the first 10–15 ms following consonant release, was systematically varied in 5‐dB steps from −10 to +10 dB relative to a ‘‘normal’’ burst amplitude for two labial‐to‐alveolar synthetic speech continua—one comprising voiceless stops and the other, voiced stops. The distribution of spectral energy in the bursts for the labial and alveolar stops at the ends of the continuum was consistent with the spectrum shapes observed in natural utterances, and intermediate shapes were used for intermediate stimuli on the continuum. The results of identification tests with these stimuli showed that the relative amplitude of the burst significantly affected the perception of the place of articulation of both voiceless and voiced stops, but the effect was greater for the former than the latter. The results are consistent with a view that two basic properties contribute to the labial–alveolar distinction in English. One of these is determined by the time course of the change in amplitude in the high‐frequency range (above 2500 Hz) in the few tens of ms following consonantal release, and the other is determined by the frequencies of spectral peaks associated with the second and third formants in relation to the first formant.

ISSN:0001-4966    

DOI:10.1121/1.389856

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

Acoustic analyses of vowel–consonant–vowel (VCV) utterances indicate that they generally include formant transitions from the first vowel into a period of closure (VC transitions), and transitions out of the closure into the second vowel (CV transitions). Three experiments investigated the perceptual importance of the VC transitions, the CV transitions, and the closure period in identification of medial stop consonants varying in place of articulation. Experiment 1 compared identification of members of synthetic VC and CV continua with those from VCV series made by concatenating corresponding VC and CV stimuli using various closure durations. Experiment 2 examined identification of VCV stimuli constructed with only VC, only CV, or both VC and CV transitions; again closure duration was systematically varied. Experiment 3 correlated CV and VC identification with identification of VCV stimuli. Neither closure duration nor formant transition structure (i.e., only VC, only CV, or both) had an independent effect on identification. Instead, the formant structure and closure durationtogetherstrongly affected stop identification. When both VC and CV transitions were present, the CV transitions contributed somewhat more to identification of medial stops with short closures, than the VC transitions did. With longer closure durations, neither set of transitions appeared to determine perceived place of articulation in any simple way. Overall, the data indicate that the perception of a medial consonant is more than simply a (weighted) sum of its parts.

ISSN:0001-4966    

DOI:10.1121/1.389857

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

Confusions between pairs of intervocalic consonants excised from connected speech were investigated under several conditions of speech degradation: digital voice processing, noise, and bandpass limiting. The distribution of the types of errors that were made, e.g., voicing, nasality, place of articulation, differed from those made on citation form syllable‐initial consonants. Intervocalic consonants that were taken from word‐initial position scored higher with no degradations than those taken from word‐medial or word‐final position, but the medial and final segments suffered less under mild degradations than did the initial ones.

ISSN:0001-4966    

DOI:10.1121/1.389858

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

The free‐field speech‐reception threshold (SRT) for sentences was investigated in quiet and under nine conditions involving noise or competing speech for a group of 20 elderly subjects (ten male, age 75–85; ten female, age 76–88) and a reference group of ten young normal‐hearing subjects. The noise source had the same long‐term average spectrum as the competing speech. The interfering signals were presented at a constant level of 55 dBA. All elderly subjects had moderate, nearly symmetrical pure‐tone hearing losses with an average loss at 500, 1000, and 2000 Hz of between 9 and 40 dBre: ISO‐389. The main results are (1) the SRT values in noise and competing speech are about equal, whereas the normal‐hearing subjects showed a lower SRT (7 dB lower for the condition that both sound sources are in front) in competing speech than in noise; apparently, the elderly subjects do not benefit from the relatively silent periods in competing speech; (2) the gain obtained by moving the interfering noise source from the front to the lateral position is only 2.5 dB, in contrast to a gain of 9.6 dB for the young subjects; apparently, the elderly are unable to make full use of the spatial divergence between primary speaker and noise source.

ISSN:0001-4966    

DOI:10.1121/1.389859

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

Children’s speech timing is often more variable than adults’. In the present study, two hypotheses that have been proposed to account for this observation are considered. One claims that children do not have neuromotor control capabilities comparable to adults. The other suggests that the greater variability is a statistical consequence of children’s longer segment durations. These two hypotheses were examined by having children and adults speak at both faster and slower rates than normal. Within‐group comparisons across different rates and between‐group comparisons for similar durational values were made from spectrographic measurements. Results indicate that both statistical and neuromotor factors seem to contribute to the greater variability commonly observed in children’s speech.

ISSN:0001-4966    

DOI:10.1121/1.389860

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP