摘要:

Contact between fingers and thumb on a task of counting on one's fingers was related to lip/jaw and laryngeal movements while simultaneously counting aloud. Finger contacts were measured from the onset of a voltage produced as the contact completed a circuit. Speech movements were inferred from the deflections of a LED attached to the lower lip of the speaker and from the slow and fast (filtered) impedance changes recorded by an electroglottograph. Subjects counted 20 four‐digit number series composed of the numbers 2, 3, 4, and 5. They were instructed to simultaneously count aloud and on their fingers, the second task providing more uncertainty than the first. Results showed that subjects timed finger contacts most closely with the movements of lip/jaw lowering and vocal fold adduction preparatory to voicing, rather than with voicing itself. These results add physiological evidence to acoustic data previously reported by G. Allen [Lang. Speech15, 72–100 (1972)], K. Rapp [Pap. Linguist., Univ. Stockholm8, 14–19 (1971)], and C. A. Fowler and L. G. Tassinary [Attention and Performance IX, edited by Long and Baddeley (Erlbaum, Hillsdale, NJ, 1981), pp. 521–535] indicating that the systems may be coordinated on the basis of the most dynamic parts of the utterance rather than the relatively steady state portions. [Work supported by NIH.]

ISSN:0001-4966    

DOI:10.1121/1.2022394

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

In a previous study [B. Lyberg, J. Phonet.9, 97–103 (1981)] quite strong evidence was found in favor of a relationship between segment duration and fundamental frequency change in certain positions of an utterance such as the phrase final position. The speech material used in the study was built up of Swedish words containing only phonologically long vowel segments. In the present investigation this relationship was studied once more but this time for both phonologically long and short vowel segments in order to elucidate the interaction between the signaling of the quantity distinction and the fundamental frequency contour. The results show that the segment duration of the stressed vowel in monosyllabic words in phrase final position is positively correlated with the fundamental frequency change of the terminal fall when the vowel is followed by a voiced consonant for both phonologically short and long vowels. When the vowel is followed by a voiceless consonant the terminal fall seems to be compressed in the time dimension.

ISSN:0001-4966    

DOI:10.1121/1.2022397

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

An experimental investigation of signal amplitude and phase fluctuations under Arctic conditions has been conducted. The data were sampled from low‐frequency cw transmissions during the FRAM IV experiment in April 1982. The signals were generated at the Tristen ice camp and received at the FRAM IV ice camp located north of Spitzbergen. The average water depth along the propagation paths was 3000 m. The range was approximately 275 km. The 28 receivers were positioned along a vertical array at depths from 30 to 960 m. The single hydrophone data exhibited a high signal‐to‐noise ratio (⩾10 dB) and a high phase stability. The measured phase was modified by means of a frequency shift to compensate for relative platform motion. Histograms of the single hydrophone amplitude and phase were examined for goodness of fit to hypothetical density functions. Amplitude and phase distributions were consistent with a multipath fluctuation model, at the 0.05 level of significance. These densities are associated with a partially saturated process. They were first theoretically derived by P. N. Mikhalevsky [J. Acoust. Soc. Am.72, 151–158 (1982)].

ISSN:0001-4966    

DOI:10.1121/1.2022404

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

Oceanographic data (CTD and XBT profiles) were obtained in the summer of 1983 on a transect from within the marginal sea ice zone (at about 76° 30′ N Lat) across the northern Greenland and Norwegian Seas to Tromsø, Norway. The initial 150‐km section embraces the complex frontal zone between waters of polar origins in the upper layer of the East Greenland Current and Arctic waters of the Greenland Sea gyre. Interposed between these two water types is a warmer, more saline water of Atlantic origin. The data from this 150‐km section have been used as input for an environmental range‐dependent sound propagation model (GRASS). By independently limiting the number of bottom bounces and refractive turning points, insight is gained into the contribution of each principal propagation mode: bottom bounce, surface duct, and convergence zone for various source and receiver depths. The relative importance of each propagation mode to the total propagation loss is presented as a function of range from the East Greenland Current end of the section. [Work supported by ONR and NUSC.]

ISSN:0001-4966    

DOI:10.1121/1.2022405

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

A transient gravimetric method is described by which force gauge response characteristics are determined by measuring the response of the force gauge to a unit step force input which is created by suddenly lifting a known mass from the gauge. Absolute estimates of gauge sensitivity and frequency response can be obtained directly from the time history by measuring the response step height and time decay parameters or by taking the time derivative of Fourier transform of the time history. Magnitude and phase errors associated with the basic technique and the processing options will be examined and compared to currently accepted approaches. Of particular concern in this study are phase errors of the order of three degrees or less which have been shown by the authors to yield significant inaccuracies in power flow measurements [J. Acoust. Soc. Am. Suppl. 176, S66 (1984)]. Results of an investigation of cable motion induced case strain on force gauge response performed using a lift test in conjunction with a vibration shaker test will be described. [Research supported by David Taylor Naval Ship Research and Development Center, Washington. DC.]

ISSN:0001-4966    

DOI:10.1121/1.2022413

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

An impact on the rim of a railroad wheel causes a wave which travels around the rim at a constant speed. The reflection of this rim wave from a thermal crack can be isolated from other traveling wavelets by using a complex cepstrum analysis. The power cepstrum has already been used to detect the presence of a hand‐made surface crack in a wheel rim [M. N. Fahmy and R. D. Finch, J. Acoust. Soc. Am.75, 1283–1290 (1984)]. Signals from three wheels with different crack sizes and types were analyzed and the ratio between the maximum amplitude of the reflection echo to the maximum amplitude of the incident wavelet (AR) was measured. The AR values measured experimentally were compared with values obtained theoretically. Field data were collected from a test consist train having wheels with different known defective conditions. Both power and complex cepstrum analysis were used in the analysis of the field data and the detection rate was 91% and the false alarm rate was 28%. In the cepstrum analysis, the aliasing error was measured and the minimum phase condition was used with the complex cepstrum analysis.

ISSN:0001-4966    

DOI:10.1121/1.2022420

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

The Kirchhoff‐Helmholtz integral equation yields a variational principle for the pressure on the surface of a vibrating body [A. D. Pierce and X.‐F. Wu, J. Acoust. Soc. Am. Suppl. 174, S107 (1983)]. A comparable principle is derived here for wave diffraction by a rigid body. Both versions offer the prospect of a more efficient treatment of diffraction effects than other methods, such asTmatrices and the doubly asymptotic approximation. As a first application, algorithms for the evaluation of the pressure on the surface of a vibrating disk are derived and developed for constant frequency excitation and an axisymmetric surface pressure. For radiation, this situation arises when the vibrational pattern is axisymmetric. Axisymmetry for the reflection problem is obtained for low values ofkaat arbitrary incidence, or else for normal incidence at arbitraryka. The variational principles are used to derive system equations associated with (1) assumed mode functions and (2) finite elements. In the former, a sequence of admissible functions are selected to represent the surface pressure, and the variational principle provides the best combination of (complex) amplitudes describing the overall contribution of each mode. The finite element version yields simultaneous equations for the pressures at the nodes of the finite element mesh. In both techniques the system equations are simultaneous linear algebraic equations. The only difference in the treatment of the radiation and reflection problems is the inhomogeneous terms in the equations. [Work supported by ONR.]

ISSN:0001-4966    

DOI:10.1121/1.2022427

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

The Green function approach has been of great benefit in linear acoustics. But there are occasions when an uncritical use of this conceptual picture of the source distribution as a collection of elementary point sources can lead to paradoxical and misleading conclusions, especially when the physical problem takes account of nearby boundary surfaces. Further, with the Lighthill acoustic analogy, in the vicinity of the point source the nonlinear terms may dominate. In this paper we determine the neighborhood of the point source within which, even in linear problems, the existence of boundaries and/or other sources will preclude the use of unmodified “point source” ideas. The derivation relies on the rigorous utilization of the mutual impedance concept, and gives an effective size which is multipole‐order and radiation wavelength dependent. For radiators at low frequency this may exceed the classical “nearfield limit.” Some of the problems referred to earlier—in particular for turbulent flow noise over rough boundaries—are shown to lie in domains where moderating influences exist in the “farfield” of a source but within its effective dimensions.

ISSN:0001-4966    

DOI:10.1121/1.2022430

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

The hearing thresholds for 40 young adults (18–26 years) were measured at 13 frequencies (8, 9,…,20 kHz) using a newly developed high‐frequency audiometer. All subjects were screened at 15‐dB hearing level at the low audiometric frequencies, had tympanometry within normal limits, and had no history of significant hearing problems. The audiometer delivered sound to the ear canal through a tube and earpiece in which a small calibrated microphone was located. For each ear, a calibration function relating sound pressure at the inner end of the ear canal to voltage at the acoustic source was calculated from an impulse recorded at the microphone. Calibration functions for different ears extended over a range of 15 dB at some frequencies. For some subjects cross modes in the ear canal prevented accurate calibration at the highest frequencies. Most high‐frequency audiograms exhibited a sharply sloping increase in threshold. The location in frequency of this abrupt increase in threshold differed considerably among different subjects and appeared to provide the best characterization of an individuals's high‐frequency hearing. [Supported by a contract from NINCDS.]

ISSN:0001-4966    

DOI:10.1121/1.2022438

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

The effect of varying the on‐time and off‐time of interrupted pure tones on threshold of Bekesy tracings was discussed for subjects showing sensorineural hearing loss with abnormal adaptation. In the majority of subjects, with a fixed long on‐time, threshold increased as the off‐time was shortened. When the off‐time was shorter than a critical value, threshold approached that for continuous tones. There was insignificant change in threshold when the on‐time was varied with a fixed long off‐time. However, some subjects showing abnormal adaptation demonstrated no observable change in threshold as the off‐time was shortened with a fixed on‐time. In the differential diagnosis of these cases, organic hearing loss due to multiple sclerosis or some other unknown causes and nonorganic hearing loss should be considered. Above finding was compared and discussed with other audiological test results obtained in these cases.

ISSN:0001-4966    

DOI:10.1121/1.2022441

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP