摘要:

High‐damping materials have become to be interesting for noise control and vibration damping. Fe‐Cr‐Al alloy is called Silent alloy and shows high mechanical strength in addition to its high damping capacity. The acoustic shock pulse was used in order to obtain the fundamental data of the acoustic characteristics for longitudinal wave of this alloy. The amplitude dependence of attenuation and propagation velocity of acoustic shock pulse was measured at room temperature. The attenuation constant increases as the amplitude of shock pulse increases, and shows a maximum value at about 6.5 × 10−5. The propagation velocity of shock pulse slightly decreases with increasing the amplitude of shock pulse. To obtain the clear amplitude dependence of attenuation constant and propagation velocity, it is necessary to measure them in the higher amplitude range.

ISSN:0001-4966    

DOI:10.1121/1.2004154

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Acousticians have largely overlooked the methods ofcomputational fluid dynamics(i.e., the direct numerical integration of the nonsteady, compressible continuity, momentum, and energy equations) because of the success of the linearized normal‐mode approach and because the numerical viscosity inherent in traditional computational methods damp out acoustic disturbances at an unrealistic rate. The advantage of the computational approach is that it allows inclusion of physical phenomena excluded from the linearized normal‐mode approach such as nonlinear convection, nonisentropic losses, and phase change effects. The recent development ofSHASTA, a relatively nondiffusive computational method [J. P. Boris and D. L. Book, J. Comp. Phys.11, 38–69 (1973)], has made possible the accurate solutions to acoustics problems.SHASTAis applied to a piston driven shock wave, an acoustic traveling wave, and an acoustic standing wave. The solutions of these problems by other standard numerical schemes are shown for comparison. It is found that onlySHASTAis acceptable for all problems considered. As a practical example the computational approach is applied to the acoustic‐wave/entropy‐wave interaction associated with reflections from a choked flow wall. [Work supported by DARPA.]

ISSN:0001-4966    

DOI:10.1121/1.2004158

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

For some applications of parametric acoustic sources, broader beams than can be obtained from plane‐piston primary projectors are desired. Beam broadening via focusing and divergent lenses is described. The lenses, molded from silicone rubber, had an aperture of 23 cm, but the difference frequency source levels and beam patterns were equivalent to those from plane‐piston sources of diameter 3.5 cm for the focusing lens and 2.3 cm for the divergent lens. The primary frequency was 260 kHz, and the difference frequencies ranged from 2.6 to 52 kHz. [Work sponsored by Naval Sea Systems Command.]

ISSN:0001-4966    

DOI:10.1121/1.2004161

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

In order to make it clear which is more important for sound localization in the median plane, SP cues (spectral cues) or ID cues (interaural difference cues), two localization tests of sound sources simulated by a digital computer using measured individual head‐related transfer functions (M. Morimotoet al., 9th ICA, H47 (1977)] were carried out. First, SP cues were presented to the subjects keeping interaural differences of all stimuli constant. Second, to the contrary, ID cues were presented to them keeping all spectra at one ear constant. The results of those tests are the following. (1) All subjects can localize stimuli with only SP cues. but they cannot localize so accurately as stimuli with the both cues. (2) They cannot localize stimuli with only ID cues at all. Those results show that SP cues are far more important than ID cues for sound localization in the median plane, however, that ID cues should not be neglected.

ISSN:0001-4966    

DOI:10.1121/1.2004166

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Previous research using repeatable samples of noise, frozen noise, has concentrated on evaluating models of signal detection [A. Ahumuda, Jr., R. Marken, and A. Sandusky, J. Acoust. Soc. Am.57, 385–390 (1975)] or estimating the “internal” noise of the auditory system [D. M. Green, Psychol. Rev.71, 392–407 (1964)]. The present research investigates the detectability of a 500‐Hz sinusoid, masked with different samples of frozen noise under both diotic and dichotic conditions. The results from several samples of noise and starting phase angles of the sinusoid will be presented. The data show differences in detection across different samples of noise as well as differences between diotic and dichotic conditions. The ability of various theories of binaural processing to account for the results will be discussed. [Work supported by NSF research Grant BNS‐77‐17308 and PHS Mathematical Psychology Training Grant MH‐11219.]

ISSN:0001-4966    

DOI:10.1121/1.2004170

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Masked threshold for a phase incremented pulsed tone atfh+f1or at 2fh+f1was measured in the presence of phase‐synchronized maskersfhandf1. The frequency off1was either 250, 500, or 1000 Hz and the ratiofh/f1was fixed at 1.2. The amplitude of the menaural phase effect varied with the level of the primaries, being smaller at the high and low extremes of the range of primary amplitudes. Growth of masking is frequency dependent. Combination tone estimates were calculated based on the assumption that the menaural phase effect is the result of interaction between an aural combination tone and the maskee. Analysis of the growth rates does not permit rejection of a frequency‐independent nonlinear mechanism for their generation.

ISSN:0001-4966    

DOI:10.1121/1.2004177

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

The present study examined the flexibility of the auditory system to integrate energy spread over a band of frequencies. Minimum spectral integration can be measured when a single tone is masked by various bandwidths of noise (a “critical‐band” experiment); maximum spectral integration can be examined when a signal noise, of various bandwidths, is masked by wideband noise. The present study compares these two measures directly by employing the same stimuli and experimental procedures. Digitally synthesized noise, with essentially rectangular spectra (3000‐dB/octave skirts), was used either as masker or signal. In the first case, when the masking noise bandwidth was varied, just‐detectable signal level for a 1000‐Hz tone increased at 1.7 dB/octave untilWm= 70–110 Hz and then remained essentially constant. In the second case, when signal bandwidth (centered at 1000 Hz) was varied, just‐detectable signal level was essentially constant untilWs= 70–110 Hz and then increased at 1.7 dB/octave. The coincidence of the two breakpoints suggests a simple critical‐band estimation procedure derived from two thresholds: a tone in wideband noise and a wideband signal in a wider‐bandwidth noise. Based on the predictions for the energy‐detector model, a 1.5‐dB/octave slope implies an efficient spectral integration over the signal bandwidth. Combined with Green's similar slope, the present results indicate that the maximum limit of spectral integration may be at least 3 kHz wide. Additional results suggest abrupt spectral edges in masking noise without a wideband background slightly interferes with a simultaneous signal; the effect is similar to nonsimultaneous suppression/inhibition effects, although the cause may not be the same. [Work supported by NIH.]

ISSN:0001-4966    

DOI:10.1121/1.2004180

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

It is generally agreed upon that the criterion of a subject varies during an experiment, and that this variability is proportional to the number of criteria a subject must maintain. To assess response variability, two experimental methods were employed, one having a fixed signal‐to‐noise ratio (SNR) and the other a variable SNR. The task involved detecting a 500‐Hz centered band of noise presented in noise. Subjects responded on a size‐point confidence rating scale indicating their decision regarding the presence or absence of the dichotomous band. Within the context of a larger study in which data from 48 experimental sessions were collected, four subjects each listened to 15 prerecorded experimental sessions twice. Correlations were obtained for each method at a variety of SNRs, each based on 24 or 30 pairs of responses. The average correlations for the fixed and variable methods were 0.91 and 0.27, respectively, and were related to the SNR of the signal. Implications for repeated measures designs and pooling of data are discussed.

ISSN:0001-4966    

DOI:10.1121/1.2004189

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Recent developments in the techniques for physiological observation and acoustical analysis have made possible the accumulation of a large amount of valuable data on the process of speech production. Quantitative interpretation and effective utilization of these data will be facilitated by introducing appropriate models for the relationships between these data and the underlying linguistic information, as well as for relationships between physiological and acoustical data. This session will focus on various models of the speech production process and their applications to speech analysis and synthesis.

ISSN:0001-4966    

DOI:10.1121/1.2004194

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

A previous paper showed how the vocal tract shapes of American English vowels can be generated from three formant frequencies. This algorithm has now been augmented and tested on short utterances containing predominately vocalic segments such as "Where were you a year ago?" Three subjects were recorded saying phrases of this type. Formant frequencies were determined every 10 ms and used to calculate possible underlying components of tongue and lip shape. These components were used to produce sequences of sagittal section diagrams of the vocal tract. Some consonantal effects were taken into account by means of simple rules (e.g., the tongue tip was moved towards a retroflex position whenF3was lowered). Given appropriate formant frequencies, plausible sequences of movement of the vocal organs were generated. Since the same set of formant frequencies can correspond to different vocal tract shapes, no claim can be made that these particular movements were used by these particular speakers. But, throughout most of the utterances, vocal tract shapes were generated thatcouldhave produced the observed formant frequencies.

ISSN:0001-4966    

DOI:10.1121/1.2004199

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP