摘要:

Until fairly recently it has not been possible to perform exact calculations of scattering from nonspherical three‐dimensional elastic shells. However, due to the extended boundary condition method (EBC) of Waterman, such calculations are presently possible. Both as a check of current numerical codes, and because of an interesting physical observation, a comparison of scattering from submerged spherical shells, and end‐on incident scattering from spheroidal shells of the same material are presented in this work. The spherical calculations are performed using a normal mode code and the spheroidal calculations are performed using a code based on the EBC method for aspect ratios ranging from 1 to 3 for two different shell thicknesses. A comparison of the spheroidal form function with that of the spherical case illustrates a one‐to‐one correspondence between the two in which the form function of the spheroidal cases appear as stretched spherical calculations. This stretching effect is easily explained using the standing wave theory of resonances proposed by Werby and Gaunaurd.

ISSN:0001-4966    

DOI:10.1121/1.2023948

出版商:Acoustical Society of America    

年代:1986

数据来源: AIP

摘要:

Auditory duration DLs at 2 kHz were measured in Old World monkeys (Macaca, Cercopithecus) and humans using a repeating standard AX procedure and positive reinforcement operant conditioning techniques. For a 200‐ms standard tone, monkey DLs (45–62 ms) were about 2–3 times larger than human (15–27 ms), Weber fractions (ΔT/T) for all species were smallest at standard durations of 200 and 400 ms and increased with decreasing standard duration. DLs for all species did not vary as a function of sensation level from 30 to 60 dB, but were elevated slightly at 20 dB. Monkeys experienced difficulty in discriminating duration decrements, in contrast to humans. Results are related to other comparative psychoacoustic data and vocal communication. [Work supported by NSF and the Guggenheim Foundation.]

ISSN:0001-4966    

DOI:10.1121/1.2023959

出版商:Acoustical Society of America    

年代:1986

数据来源: AIP

摘要:

Rybaket al.[J. Pharmacol. Exp. Therapeut.230, 706–709 (1984)] demonstrated that i.v. injection of 100 mg/kg FU results in a rapid but transient accumulation of the drug in ST of the chinchilla (CH). We found a similar pattern in ST of guinea pigs (GP) (5 μg/ml, 15 min after 100 mg/kg i.v.), followed by a (gradual) decline to 0.8 mg/ml within 1 h. In SV (not studied by Rybaket al.) FU increased very slowly (0.8 μg/ml at 15 min) but continued to rise gradually (2 μg/ml at 1 h). Rybaket al.found that 50 mg/kg PR suppressed accumulation of FU, while we found only much higher dosages (200 mg/kg) to be effective in GP. Paradoxically, at low dosages (50 mg/kg) PR caused an increase of FU that persisted for prolonged periods. This suggests that the influx and outflux systems for FU at the blood/perilymph barrier of ST have a differential sensitivity to PR, perhaps analogous to the differential modification of methotrexate flux in and out of tumor cells in response to PR [Henderson and Zevely, J. Biochem. Pharmacol.34, 1725–1729 (1985).]

ISSN:0001-4966    

DOI:10.1121/1.2023963

出版商:Acoustical Society of America    

年代:1986

数据来源: AIP

摘要:

Confusion matrices for seven synthetic steady‐state vowels were obtained from ten normal and three hearing‐impaired subjects. The vowels were identified at greater than 96% accuracy by the normals, and less accurately by the impaired subjects. Shortened versions of selected vowels then were used as maskers; vowel masking patterns (VMPs) consisting of forward‐masked thresholds for sinusoidal probes at all vowel masker harmonics were obtained from the impaired subjects and from one normal subject. Here VMPs of the impaired subjects, relative to those of the normal, were characterized by smaller dynamic range, poorer peak resolution, and poorer preservation of the vowel formant structure. These VMP characteristics, however, did not necessarily coincide with inaccurate vowel recognition. Vowel identification appeared to be related primarily to VMP peak frequencies rather than to relative peak amplitudes or between‐peak characteristics of the patterns. [Work supported by NINCDS.]

ISSN:0001-4966    

DOI:10.1121/1.2023968

出版商:Acoustical Society of America    

年代:1986

数据来源: AIP

摘要:

Single‐channel vibro‐tactile discrimination and identification of vowels was assessed using a scheme which maintains the spectral shape of the complex speech waveform. A series of vowels and diphthongs were synthesized using the Klatt algorithm. Unlike conventional synthesis, the formant frequencies were set such that the first four formants fell under 660 Hz and the formant bandwidths were narrowed. This synthesis effectively generated 5:1 frequency compression. The synthesized segments sound speech like. Naive subjects were presented both discrimination and identification tasks. The stimuli were felt with a Audiological Engineering V1220 transducer. With no prior exposure discrimination exceeded 7%, and within a few hours of testing discrimination levels of 95% were achieved. Subjects were able to accurately identify many of the vowel segments. Furthermore examination of the confusions reveals patterns similar to those reported for auditory confusions of natural vowels. These findings appear to contradict the premise underlying the development of multichannel tactile aids and cochlear implants that the tactile senses and the impaired ear are incapable of extracting the appropriate information from a single complex speech waveform.

ISSN:0001-4966    

DOI:10.1121/1.2023971

出版商:Acoustical Society of America    

年代:1986

数据来源: AIP

摘要:

We have developed an integrated voice analyzer (IVA) using DSP (TMS32010) to achieve high‐speed acoustic analyses of a sustained vowel. A personal computer connected to the IVA is employed as the man‐machine interface as well as to display and save various analysis results. The IVA has many functions, such as detecting vocal noise by an adaptive comb filter, measuring period and amplitude perturbation quotients, calculating DFT spectra and LPC coefficients, etc. The results are stored into a disk file to do statistical analysis or to perform further analyses. This system provides an interactive acoustic analysis method for quantitative evaluations of the pathological voice arising in various voice research and clinical areas. We describe an application of the IVA for the clinical screening system for pathological voices, where hoarseness grade (HG) of a voice can be obtained from five sustained phonations. [Work supported by a Japanese Grant‐in‐Aid for Scientific Research.]

ISSN:0001-4966    

DOI:10.1121/1.2023979

出版商:Acoustical Society of America    

年代:1986

数据来源: AIP

摘要:

A number of studies have been devoted to the description of the prosodic characteristics of esophageal speakers. However, pitch extraction of esophageal speech is difficult because of its low pitch, of the often quasi‐periodic character of the vibration of the pharyngo‐esophageal segment, and because stoma noise may be added to the signal. Commercially available hardwareF0extractors often produce artefacts in the analysis of esophageal speech. Consequently it may be asked whether the harmonic source model of laryngeal speech is inappropriate for esophageal speech, or whether it simply constitutes an extreme of this model in terms of the proportion of noise it contains. In a number of recent studies, cepstral analysis has been applied to pitch extraction of esophageal speech. This procedure handles low fundamentals well, but is computationally slow and complex. In this study, several other pitch extraction algorithms which are computationally simpler than the cepstrum will be compared to cepstral analysis in regard to their adequacy forF0extraction with esophageal speech. Some of these, especially the harmonic product spectrum and the harmonic sum spectrum, have been shown to be superior to the cepstrum in the analysis of noise speech signals. [Work supported by the Norris Cancer Hospital, USC.]

ISSN:0001-4966    

DOI:10.1121/1.2023985

出版商:Acoustical Society of America    

年代:1986

数据来源: AIP

摘要:

An ensemble of active and passive satellite remote sensors are presently operating or will be launched in the near future that provide high resolution detailed oceanographic information on a synoptic scale. These sensors operate in the visible, infrared, and microwave region of the electromagnetic spectrum and include the NOAA 7/8 (TIROS), NIMBUS‐7, LANDSAT, SPOT, and GEOS satellites presently in orbit as well as the planned ESA ERS‐1, NROSS, TOPEX, RADARSAT, and JERS‐1 satellite launches. The information provided by these satellites includes not only ocean surface and air/sea environmental information such as wind speed and direction, gravity wave spectral estimates, surface water height, salinity, temperature, and water vapor content, but also information about the interior of the water column (i.e., fronts, upwelling, and internal waves). Additional information about the ice‐covered ocean can also be provided by these satellite data. The sea ice information includes; ice edge location, ice concentration, floe size distributions, ice type, and ice kinematics. The merging of remote sensing data with acoustical data can potentially provide new insight into understanding the interior structure of the ocean. The use of acoustical data to aid in the interpretation of remote sensing oceanographic data can in turn increase the use of the satellite information.

ISSN:0001-4966    

DOI:10.1121/1.2023989

出版商:Acoustical Society of America    

年代:1986

数据来源: AIP

摘要:

Quasisynoptic ocean data sets consisting of thermal sections of data collected from deep (800‐m) Airborne Expendable Bathythermographs (AXBTs) and sea surface topography measured by overflights of the U.S. Navy GEOSAT altimetric satellite are presented and analyzed. These data, collected as part of the NW Atlantic Regional Energetics Experiment (REX) during August 1985, cover a significant portion of the Gulf Stream front from approximately 57°W to 68°W including three warm meanders and the intervening two cold meanders. Additionally, two warm core rings and one Sargasso cold core ring are included in the region mapped during the six‐day period of the AXBT survey. Using climatological regression between the dynamic thickness (0/3000 dbar) and isotherm depth, thesein situthermal data are compared with sea surface topography as measured by the GEOSAT altimeter. These data sets form the basis of the range‐dependent acoustical model runs discussed in detail in a jointly submitted invited paper NN3 in this session.

ISSN:0001-4966    

DOI:10.1121/1.2023995

出版商:Acoustical Society of America    

年代:1986

数据来源: AIP

摘要:

A new method is presented for estimating the arrival times of overlapping signal pulses that are separated by less than the duration of the signal autocorrelation function. The method is based on the observation that if the signal has a flat band‐limited spectrum, then the maximum‐likelihood estimator for the time of arrivals can be approximately transformed into an equivalent high‐resolution exponential parameter estimation problem. Then, an improved linear prediction algorithm [D. W. Tufts and R. Kumaresan, Proc. IEEE70, 975–989 (1982)] for high resolution exponential parameter estimation is used to estimate the time of arrivals. The proposed method is computer simulated for two linear FM sweep signal pulses at various separations and signal‐to‐noise ratios. The simulation results are compared to the Cramer‐Rao lower bound (CRLB). These results indicate performance close to the CRLB over a reasonable range of pulse separation and signal‐to‐noise ratios.

ISSN:0001-4966    

DOI:10.1121/1.2023999

出版商:Acoustical Society of America    

年代:1986

数据来源: AIP