摘要:

Full analytic solutions of the internal stress field and the radiated ultrasonic wave are obtained for a thickness‐mode piezoelectric transducer excited by a pulse voltage source, having or not having an internal resistance. Two mechanisms of transduction as well as the effect of the internal resistance on these are drawn from the complete solutions. The negative capacitance in the Mason equivalent circuit is interpreted in terms of the identified mechanism of the acoustoelectrical regenerative vibration.

ISSN:0001-4966    

DOI:10.1121/1.390034

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

Intra‐articulator anticipatory and carryover coarticulation were assessed in both temporal and spatial terms. Three subjects produced VCV sequences with velar stop consonants and back vowels. Pulsed ultrasound was used to examine the vertical displacement, duration, and maximum velocity of the tongue dorsum raising (VC transition) and lowering (CV transition) gestures. Anticipatory coarticulation was primarily temporal for two subjects, with decreases in the duration of the VC transition accompanying increases in displacement for the CV transition. Carryover coarticulation was primarily spatial for all three subjects, with decreases in CV displacement and maximum velocity accompanying increases in VC displacement. It is suggested that these intra‐articulator patterns can be accounted for in terms of an interaction between the raising gesture and a vowel‐specific onset time of the lowering gesture towards the vowel. The implications of this kinematic characterization are discussed.

ISSN:0001-4966    

DOI:10.1121/1.390035

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

Previous experiments on the perception of initial stops differing in voice‐onset time have used sounds where the boundary between aspiration and voicing is clearly marked by a variety of acoustic events. In natural speech these events do not always occur at the same moment and there is disagreement among phoneticians as to which mark the onset of voicing. The three experiments described here examine how the phoneme boundary between syllable‐initial, prestress /b/ and /p/ is influenced by the way in which voicing starts. In the first experiment the first 30 ms of buzz excitation is played at four different levels relative to the steady state of the vowel and with two different frequency distributions: In theF1‐only conditions buzz is confined to the first formant, whereas in theF123 conditions all three formants are excited by buzz. The results reject the hypothesis that voicing is perceived to start when periodic excitation is present in the first formant. The results of the third experiment show also that buzz excitation confined to the fundamental frequency for 30 ms before the onset of full voicing (formant excitation) has little effect on the voicing boundary. The second experiment varies aspiration noise intensity and buzz onset intensity independently. Together with the first experiment it shows that: (1) at all buzz onset levels a change in aspiration intensity moves the boundary by about the 0.43 ms/dB found by Repp [Lang. Speech27, 173–189 (1979)]; (2) when buzz onsets at levels greater than −15 dB relative to the final vowel level, changes in buzz onset level again move the /b/–/p/ boundary by the same amount; (3) when buzz onsets at levels less than −15 dB relative to the vowel, decreasing the buzz onset level gives more /p/‐ percepts than Repp’s ratio predicts. This last result, taken with the results of the first experiment, may reflect a decision based on overall intensity about when voicing has started.

ISSN:0001-4966    

DOI:10.1121/1.390036

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

The monaural speech‐reception threshold (SRT) for sentences was investigated in quiet and under four noise conditions for 80 male subjects (age 60–90) and 30 female subjects (age 71–89). The noise levels used were 28, 43, 58, and 73 dBA. The noise had the long‐term average spectrum of speech. It is shown that a model developed by Plomp [J. Acoust. Soc. Am.63, 533–549 (1978)], which interprets any hearing loss for speech (SHL) as a combination of a loss of classA(attenuation of both speech and noise) and a loss of classD(distortion of the sound signals), enables one to make an accurate description of the SRT values measured. Fitting this model, for each individual, to the SRT data yielded values for SHL in quiet (=A+D) and in noise (=D). These individual SHL values were studied in relation to one another and in relation to such parameters as the pure‐tone average (PTA), the Fletcher Index (FI), and the increment in intelligibility score per dB near SRT. It was found that (1) subjects with the same SHL in quiet may differ considerably in their SHL in noise; (2) for an individual, PTA and FI are inaccurate measures for predicting SHL in quiet and in noise, and (3) the higher an individual’s SHL in noise, the lower is the increase per dB of the intelligibility score for sentences in noise.

ISSN:0001-4966    

DOI:10.1121/1.390037

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

An unconstrained optimization technique is used to find the values of parameters, of a combination of an articulatory and a vocal tract model, that minimize the difference between model spectra and natural speech spectra. The articulatory model is anatomically realistic and the vocal tract model is a ‘‘lossy’’ Webster equation for which a method of solution is given. For English vowels in the steady state, anatomically reasonable articulatory configurations whose corresponding spectra match those of human speech to within 2 dB have been computed in fewer than ten iterations. Results are also given which demonstrate a limited ability of the system to track the articulatory dynamics of voiced speech.

ISSN:0001-4966    

DOI:10.1121/1.390038

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

This paper examines the effects on fundamental frequency (F0) patterns of modality operators, such as sentential adverbs, modals, negatives, and quantifiers. These words form inherently contrastive classes which have varying tendencies to produce emphasis deviations inF0 contours. Three speakers read a set of 186 sentences and three paragraphs to provide data forF0 analysis. The important words in each sentence were marked intonationally with rises or sharp falls inF0, compared to gradually fallingF0 in unemphasized words. These emphasis deviations were measured in terms ofF0 variations from the norm; they were larger toward the beginning of sentences, in longer sentences, on syllables surrounded by unemphasized syllables, and in contrastive contexts. Other results showed that embedded clauses tended to have lowerF0, and negative contractions were emphasized on their first syllables. Individual speakers differed in overallF0 levels, while using roughly similar emphasis strategies.F0 levels changed in paragraphs, with emphasis going to contextually new information.

ISSN:0001-4966    

DOI:10.1121/1.390039

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

Temporal integration for a 1000‐Hz signal was determined for normal‐hearing and cochlear hearing‐impaired listeners in quiet and in masking noise of variable bandwidth. Critical ratio and 3‐dB critical band measures of frequency resolution were derived from the masking data. Temporal integration for the normal‐hearing listeners was markedly reduced in narrow‐band noise, when contrasted with temporal integration in quiet or in wideband noise. The effect of noise bandwidth on temporal integration was smaller for the hearing‐impaired group. Hearing‐impaired subjects showed both reduced temporal integration and reduced frequency resolution for the 200‐ms signal. However, a direct relation between temporal integration and frequency resolution was not indicated. Frequency resolution for the normal‐hearing listeners did not differ from that of the hearing‐impaired listeners for the 20‐ms signal. It was suggested that some of the frequency resolution and temporal integration differences between normal‐hearing and hearing‐impaired listeners could be accounted for by off‐frequency listening.

ISSN:0001-4966    

DOI:10.1121/1.390040

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

Temporary threshold shift (TTS) was measured for several different test frequencies following exposure to a 2500‐Hz tone.The intensity of the exposure tone was varied from 82 to 97 dB SPL; its duration was 5 or 10 min. In each post‐exposure session, TTS was followed for four test frequencies using a method of adjustment. In all cases, the ‘‘center of balance’’ of the TTS pattern moved upward in frequency as exposure intensity increased. This outcome is consistent with the idea of a basalward migration of the traveling‐wave envelope with increasing exposure intensity, but the evidence is not unequivocal.

ISSN:0001-4966    

DOI:10.1121/1.390041

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

Masking patterns obtained with forward‐masking paradigms and relatively intense maskers sometimes have their peaks at the masker frequency and sometimes at a frequency well above it. Here it is shown that which outcome is obtained depends upon certain temporal parameters of the procedure. Specifically, the masking pattern for a 2000‐Hz tone showed a gradual shift toward higher frequencies as masker intensity was increased from 65 to 95 dB SPL when long signals (about 50 ms) and long masker‐to‐signal intervals (about 50 ms) were used, but the effect was absent or smaller when the signals and intervals were short. This shift did not occur with a 750‐Hz masker. Upward shifts in the masking pattern with increasing masker intensity are in accord with the view that the peak of displacement of the traveling‐wave envelope migrates basally with increasing intensity—an idea that has frequently been suggested as an explanation of the so‐called half‐octave shift so routinely seen in auditory fatigue experiments.

ISSN:0001-4966    

DOI:10.1121/1.390042

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP

摘要:

Frequency resolution and three tasks of frequency discrimination were measured at 500 and 4000 Hz in 12 normal and 12 hearing‐impaired listeners. A three‐interval, two‐alternative forced‐choice procedure was used. Frequency resolution was measured with an abbreviated psychoacoustical tuning curve. Frequency discrimination was measured for (1) a fixed‐frequency standard and target, (2) a fixed‐frequency standard and a frequency‐transition target, and (3) frequency‐transition standard and a frequency‐transition target. The 50‐ms frequency transitions had the same final frequency as the standards, but the initial frequency was lowered to obtain about 79% discrimination performance. There was a strong relationship between poor frequency resolution and elevated pure‐tone thresholds, but only a very weak relationship between poor frequency discrimination and elevated pure‐tone thresholds. Several hearing‐impaired listeners had normal discrimination performance together with pure‐tone thresholds of 80–90 dB HL. A slight correlation was found between word recognition and frequency discrimination, but a detailed comparison of the phonetic errors and either the frequency‐discrimination or frequency‐resolution tasks failed to suggest any consistent interdependencies. These results are consistent with previous work that has suggested that frequency resolution and frequency discrimination are independent processes.

ISSN:0001-4966    

DOI:10.1121/1.390043

出版商:Acoustical Society of America    

年代:1983

数据来源: AIP