摘要:

A synthetic‐work approach was employed in an investigation of the effects of 90‐dB continuous and periodic 96‐dB intermittent broad‐band noise on human performance. Ten Navy and Air Force ROTC cadets worked the tasks of a multiple‐task performance battery (MTPB) 12 h a week (in three, 4‐h sessions) during a 4‐week training period. Subsequently, they were required to work 4 days, 8 h per day on a split‐shift schedule during the presence of noise, and finally, work 2 additional days on the same split‐shift schedule under quiet conditions. Mean percentage of baseline performance (a composite index of performance) was enhanced by a periodic 96‐dB intermittent noise, and the extent of the effect varied as a function of the number of tasks concurrently performed in the work situation. On the other hand, 90‐dB continuous noise neither enhanced nor degraded performance. [Research supported by the U. S. Army Behavior and Systems Research Laboratory, Army THEMIS Contract; and by U. S. Army Medical Research and Development Command.]

ISSN:0001-4966    

DOI:10.1121/1.1982627

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

In recent years, a great concern has been expressed for consumer protection and safety, especially for children. As an outgrowth of this concern, acoustical testing of potentially hazardous noise‐producing toys has been carried out at the National Bureau of Standards for the Bureau of Product Safety (FDA). This talk will discuss the work that has been done on cap pistols and carbide cannons. The discussion will focus particularly on the development of a standard firing apparatus for testing paper caps, and on the problems encountered and the solutions arrived at for testing carbide cannons.

ISSN:0001-4966    

DOI:10.1121/1.1982632

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Spoken digits, words, CV syllables, and Morse code are recognized and recalled better by the right ear than the left; nonverbal sounds, such as melodies, tones, sonar beeps, and toilet flushes are processed better by the left ear than the right. In general, however, ear differences have been obtained with dichotic, but not monaural stimulation. To account for these findings, Kimura proposed that under dichotic stimulation the ipsilateral auditory connections are inhibited, thus giving the right ear “privileged access” to the language‐dominant left hemisphere. Several findings involving monaural stimulation, verbal and nonverbal interference tasks, etc., are presented that indicate that Kimura's theory is inadequate. An alternate model based on interhemispheric transfer of information is proposed.

ISSN:0001-4966    

DOI:10.1121/1.1982638

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Perceptual processing time for brief CV syllables and steady‐state vowels was examined in a backward recognition making paradigm. Subjects were required to identify a 40‐msec target sound selected from either a consonant set (/ba/, /da/, /ga/), or a vowel set (/i/, /I/, /ε/). The target sound was followed by a different sound drawn from the same set after a variable silent interstimulus interval. The second sound interrupted the perceptual processing of the target stimulus at short interstimulus intervals. Recognition performance improved with increases in the silent interstimulus interval. One experiment examined processing time for consonants and vowels under binaural presentation. A second experiment compared consonant and vowel recognition under both binaural and dichotic presentation. The results indicated that (1) consonants require more processing time for recognition than vowels, and (2) binaural and dichotic presentation conditions produce differential effects on consonant and vowel recognition. These findings have several implications. First, speech perception is not immediate, but is the result of several distinct operations that are distributed over time. Second, speech perception involves various memorial processes and mechanisms which recode and store information at different stages of perceptual analysis. [Research supported in part by grant to Haskins Laboratories from NICHD and a PHS Bio‐Medical Sciences Grant to Indiana University.]

ISSN:0001-4966    

DOI:10.1121/1.1982641

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Often when vowel loudness is measured, only SPL, duration, fundamental frequency, and formant frequencies are considered as causes of loudness. In the present study, differences in loudness were measured which apparently are a function of the mode of laryngeal vibration. Stimuli were constructed by having speakers produce a series of vowels at a single fundamental frequency and at several sound pressure levels (SPLs). The sustained vowel sounds were then electronically equalized for SPL and presented to subjects as pairs of isolated vowels. Differences in loudness were reported by subjects when asked to make paired comparisons. Vowels with equal duration, SPL, formant frequencies, and fundamental frequency were judged to be different in loudness as a function of the phonation quality associated with the vowels' position in the voice range of the speakers.

ISSN:0001-4966    

DOI:10.1121/1.1982646

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Turbulent boundary layers were fully developed over either smooth or rough walls. Reynolds numbers based upon boundary layer thickness and freestream velocity are on the order 104. Fluctuating pressures at the boundary were investigated within a local region, where a freestream pressure gradient was applied. The flow reequilibrated to the negative pressure gradient and was self‐preserving, in the region of measurement. With a positive pressure gradient, the flow tended toward separation with increasing downstream distance and was not self‐preserving. Two flush‐mounted microphones provided pressure spectral densities and time‐autocorrelations at single points on the boundary, as well as cross spectra and cross correlations from pairs of points. The influence on wall pressure of roughness is explained in terms of its effects on the mean velocity profile. Fluctuating pressure models, which incorporate a unique dispersion relationc(f) (the phase velocitycis obtained from the cross‐spectral density) are found to be inapplicable to flows with a positive freestream pressure gradient. [Research supported by NSRDC.]

ISSN:0001-4966    

DOI:10.1121/1.1982652

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

A series of informal measurements of the mechanical driving point impedance properties of a toy xylophone and two steel drums is described. The motivating factor for these measurements was to establish the feasibility of accurate identification of the fundamental pitches for the various segmented regions of the steel drum from mechanical impedance data. Complicating factors, which limit the accuracy of these measurements, are indicated. It is shown that interesting mechanical properties of the toy xylophone can readily be demonstrated. Successful measurements were conducted upon a large steel drum which indicate that: (I) the fundamental component of the free decay or the frequency for the lowest principal resonance is nominally a major third above the indicated pitch, but that (II) variations from this tuning of ± 1 semitone are common in the lowest octave; (III) variations of ± 3 semitone are common in the upper octave; and (IV) the subjective impression of tonal purity is correlated with the absence of modal degeneracy or coupling in the fundamental mechanical resonance.

ISSN:0001-4966    

DOI:10.1121/1.1982658

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

There exists an abundance of high‐frequency scattering methods—but relatively little is known of their accuracy. Furthermore, the technical literature is significantly lacking in demonstrating the efficacy of one method of target scattering analysis versus another, and very few comparative analyses have been conducted—why? The Kirchhoff, Keller, and geometrical optics (acoustics) methods are well known, and can be applied to arbitrarily shaped bodies. Comparative results are shown for the problem of scattering from a rigid sphere to demonstrate the differences between methods. Further comparisons to the more exact wave‐harmonic and Watson series solutions emphasize the importance of establishing domains of validity for the approximate methods.

ISSN:0001-4966    

DOI:10.1121/1.1982664

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

It is difficult, if not impossible, to obtain error bounds on many solutions to high‐frequency scattering problems. Consequently, comparisons between solutions can be very helpful in establishing domains of validity. The backscattered field from a rigid prolate spheroid, ensonified by a plane wave, is calculated using the Keller, Kirchhoff, Luneberg‐Kline, and geometrical‐optics methods. These results are compared to each other, and to the more exact wave‐harmonic result. Finally, results from a finite element method, employing Schenck's CHIEF program, are compared. Limitations on the various methods are discussed.

ISSN:0001-4966    

DOI:10.1121/1.1982665

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The vibration of and the acoustic radiation from a semiinfinite taut membrane is considered. The plane of the membrane is extended by a semiinfinite rigid baffle. A compressible fluid fills the half‐space on one side of the membrane and baffle. Two types of vibration are considered: (i) natural motion of the membrane due to an incoming acoustically slow wave on the membrane incident normally on the edge, and (ii) forced motion of the membrane, the force having sinusoidal space and time dependence. The forced motion thus is somewhat analogous to the single‐mode‐vibration of a finite membrane. The shape of the membrane and the associated acoustic radiation are discussed and compared with the case when fluid loading is not present.

ISSN:0001-4966    

DOI:10.1121/1.1982676

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP