摘要:

A falling (“declarative”) nuclear pitch accent has a simple shape: an upward pitch obtrusion on the accented syllable, a fairly abrupt fall to near the bottom of the speaker's range, and a more gradual fall to the end. The synthesis algorithm in Anderson, Pierrehumbert, and Liberman (1983) decomposes this pattern into aH* pitch accent followed by anLphrase accent and anLboundary tone. It devotes four parameters to the realization of theH* accent (amount of rise, targetF0 height, target duration, target time) and two parameters to theLphrase accent (targetF0, target time). The parameters depend in part on properties of the accented syllable (e.g., prominence) and in part on characteristics of larger phrases (e.g., pitch range). The resulting time/F0 pairs are subject to interpolation and smoothing. This paper improves on the naturalness of the algorithm by incorporating findings from a recent study by Steele. In particular, the principles that determine the timing, magnitude, and alignment of theH*F0 rise and of theH* toLF0 fall have been improved.

ISSN:0001-4966    

DOI:10.1121/1.2023847

出版商:Acoustical Society of America    

年代:1986

数据来源: AIP

摘要:

The characteristic equation for plane‐wave propagation in a homogeneous floating ice plate was solved numerically to determine the phase speeds and attenuations of the first‐ and second‐order modes. While discussion of the phase speeds of the first‐order modes constitutes a review, the discussion of the second‐order modes, along with the attenuation characteristics of the modes when ice absorption is introduced, gives new insight into which modes might be observed in Arctic pack ice. Only the flexural and longitudinal waves, which exist below a frequency‐ice thickness product of 300 Hz‐m, propagate with losses less than 0.1 dB/m in ice less than 3 m thick. This is important to the study of noise from nearby ice events. Results of using a nearby explosive charge to measure the ice longitudinal wave speed and attenuation are given. The ice loss in the 40‐Hz region was found to be approximately a factor of two higher than expected from current empirical absorption values. This may be important to understanding losses from ice interaction in long range propagation. [Work supported by ONR.]

ISSN:0001-4966    

DOI:10.1121/1.2023856

出版商:Acoustical Society of America    

年代:1986

数据来源: AIP

摘要:

It has been predicted that the seismic propagation velocities of sea ice affect the propagation of sound in ice covered arctic waters. Since very little data are available on propagation velocities, a series ofin situmeasurements of propagation velocities and associated density, temperature, and salinity profiles have been made in sea ice. Seismic energy from predominantly shear or compressional wave sources was propagated over ranges of a few hundred meters to two three‐component geophone arrays. Propagation paths in smooth and in slightly rough annual ice were selected. Plate, flexural, and shear wave arrivals were clearly identified from their polarizations and particle velocities. A reduction in plate and flexural wave velocities was observed in the rough annual ice compared to the smoth annual ice.

ISSN:0001-4966    

DOI:10.1121/1.2023859

出版商:Acoustical Society of America    

年代:1986

数据来源: AIP

摘要:

The existence of a circulation of sound energy in an enclosure of square cross section was demonstrated on theoretical grounds by Preston Smith in 1963. Recent work has confirmed experimentally the flow of sound energy in a vortex pattern in various sound fields. Here it is shown that for any rectangular enclosure (e.g., a room or duct) having reflecting walls with two dimensions in the ratio of any two integers, there exists an infinite set of vortex modes, whose frequencies form a harmonic series. Also, for an enclosure in the form of a rigid circular cylinder, there exists infinite sets of vortex modes whose frequencies depend on the extreae of the Bessel functionsJm. Energy streamlines are given for some of the above modes, and their practical significance is discussed.

ISSN:0001-4966    

DOI:10.1121/1.2023862

出版商:Acoustical Society of America    

年代:1986

数据来源: AIP

摘要:

Raynaud's phenomenon of occupational origin, or thevibration syndrome of hand and arm, was first recognized in North America by Dr. Alice Hamilton in the limestone quarries of Bedford, Indiana around 1890 to 1900. It is a tribute to the American pioneers in this area that the Acoustical Society of America now formally recognizes Biological Response to Vibration as a technical area. The objective of this paper is to highlight gaps of information regarding mechanisms of vascular, neurological, and musculo‐skeletal damage caused by vibration. Also addressed is evidence that high noise level may act synergistically to the development of vibration syndrome of the hand and arm. Areas of research currently active in psychophysical and neurophysiological investigations to increase our understanding of tactile and spatial discrimination are discussed. Although the importance of sensory loss or “fine touch” is understood there is neither a proven objective scientific test with which the syndrome can be diagnosed nor is there a scale of damage assessment. Determining the exact role of the central nervous system in assessing damage from vibration is difficult in view of nonspecific symptoms reported from Eastern Europe and from Japan. To complicate matters still further, there is the possibility that repeated, rapid mechanical movements of the hand and arm associated with handling heavy tools produce Carpal Tunnel Syndrome but that the injury is not directly attributed to vibration. Therefore, it follows that there could exist an element of Carpal Tunnel Syndrome in many vibration syndrome cases. Clearly, there is an area within the framework of the Acoustical Society of America for worldwide cooperative efforts to solve many fundamental problems concerned with the effect of vibration on a hand or arm.

ISSN:0001-4966    

DOI:10.1121/1.2023868

出版商:Acoustical Society of America    

年代:1986

数据来源: AIP

摘要:

The fluctuations in received sound pressure levels at a microphone array 1 m above the ground and 5–100 m from a source 1–30 m off the ground have been recorded simultaneously with fluctuations in wind speed and temperature. The recordings were then played back through a multichannel analyzer which gives the number of acoustic cycles with peak amplitudes within 1024 amplitude intervals. Normalizing by the number of counts gives the probability of observing a given amplitude. These measurements were made at octave‐band preferred frequencies between 63 Hz and 8 kHz. At frequencies of 500 Hz and below, the probability distribution appears Gaussian. At higher frequencies, the distribution is better represented by a log normal distribution. In each case, the shape of the curve was dependent upon turbulence parameters (scale and magnitude). [Work supported by the Army Research Office.]

ISSN:0001-4966    

DOI:10.1121/1.2023870

出版商:Acoustical Society of America    

年代:1986

数据来源: AIP

摘要:

Microbubbles in the ocean may be coated by a thin film of surfactant since such substances can be abundant in natural waters. Such films may affect the optical and acoustical properties of bubbles. We investigated theoretical light scattering patterns for a spherical gas bubble (of radiusa) coated by a film of uniform thicknesshand refractive indexnfsurrounded by water of refractive indexnω = 4/3. The patterns were computed from the partial‐wave series of Aden and Kerker forkaranging from 100–2500, where 2π/kis the optical wavelength in water. The corresponding range ofais 7.5–189/μm;hranged from 0–3/μm andnfwas typically real and equal to 1.5. Noncoated bubbles exhibit coarse irradiance oscillations as the scattering angle θ decreases below a critical value for total reflection (θc= 82.8°); a broad minimum in the polarized irradiance is expected near the Brewster scattering angle θB= 106.3° [P. L. Marstonet al., Appl. Sci. Res.38, 373–383 (1982)]. Coatings shift the coarse oscillations towards larger θ whennf>nωin agreement with predictions of ray optics. If the irradiance near 82.8° is used to size bubbles, the effects of this shift are negligible for anticipated coating parameters. The minimum near θB, however, is predicted to be significantly lifted by coatings. [Work supported by NORDA and by ONR.]

ISSN:0001-4966    

DOI:10.1121/1.2023875

出版商:Acoustical Society of America    

年代:1986

数据来源: AIP

摘要:

In an earlier study [R. L. Freyman and D. A. Nelson, J. Acoust. Soc. Am. Suppl. 175, S6 (1984)], it was observed that normal subjects' frequency DLs for very short tones often do not improve monotonically as the level of the standard and variable tones is increased. In some subjects (at least at 1 kHz), performance deteriorated as the test‐tone level was increased from approximately 30—80 dB SPL, then improved again at still higher levels. The current experiment investigated the effects of broadband noise on the size of frequency DLs for short tones presented at moderately high levels. Frequency DLs for 5‐ms, 1‐kHz tones were first obtained in quiet as a function of stimulus intensity. DLs were then obtained with the signal level fixed at the SPL at which the largest DL in quiet was observed—this time in the presence of varying levels of white noise that partially masked the tones. The results indicated that changing the signal‐to‐noise ratio for fixed SPL tones produced similar changes in the frequency DL to those observed when the presentation level was varied in quiet. That is, in subjects with poorer DLs at moderately high levels in quiet, discrimination performance at those same levels improved when white noise was introduced. The size of the DL in noise was found to be comparable to that obtained in quiet when equated for SL. [Work supported by BRSG.]

ISSN:0001-4966    

DOI:10.1121/1.2023883

出版商:Acoustical Society of America    

年代:1986

数据来源: AIP

摘要:

Recent investigations raise questions about the temporal development of tuning in the auditory system [S. P. Bacon and B.C. J. Moore, J. Acoust. Soc. Am.80, in press (1986)]. They demonstrated that simultaneous masking psychophysical tuning curves (PTCs) were broader, on the high‐frequency side, when the probe tone coincided with masker onset that when it was temporally centered in the masker. We replicated their experiment in normal‐hearing listeners and extended it to hearing‐impaired listeners who demonstrated abnormal PTCs. Simultaneous PTCs for 10 dB SL 20‐ms probe tones, masked by 400‐ms masking tones, were obtained with the probe at the onset and at the temporal center of the masker. Results from normal‐hearing listeners confirmed earlier findings. However, in hearing‐impaired listeners there was little change in PTC shape with temporal position. These data suggest that the mechanism responsible for the temporal effect in normal ears are ineffective in listeners with sensorineural hearing loss. [Work supported by NINCDS.]

ISSN:0001-4966    

DOI:10.1121/1.2023886

出版商:Acoustical Society of America    

年代:1986

数据来源: AIP

摘要:

A factor model for midsagittal x rays of the Icelandic long and short vowels [i, I, e, y, ø, u, o, a] [M. Pétursson, Phonetics29(1–2), 22–79 (1974); M. Pétursson,Les Articulations de l'Islandais à la Lumière de la Radiocinématographie(Klincksieck, Paris, 1974)] was constructed. The factor model is based on single frames from the center of the vowels, and accounts for 95% of the variance in tongue positions with three factors. Sequences of x rays of the long and short diphthongs [ei, øi, ai, ou, au]including portions of the consonantal on‐ and off‐glides can be described by the same factors (>80% of the variance accounted for). We approximate the trajectories of the diphthongs by constructing curves that interpolate the measured positions in factor space. Examining the trajectory through factor space suggests an articulatory parametrization of diphthongs. [Work supported by NIH.]

ISSN:0001-4966    

DOI:10.1121/1.2023893

出版商:Acoustical Society of America    

年代:1986

数据来源: AIP