摘要:

The elements essential to a new vortex theory of edgetones are described with the aid of a simple flow model valid for small edges. It is shown how both the feedback to the orifice and the sound radiation may be directly attributed to the velocity field of the vortex cast off from the edge together with the sympathetic circulation about it. An upper limit to the intensity of the edgetone is discussed when the edge is very small; it depends on the size of the edge. It is shown how the small edge used by Lenihan and Richardson is quite adequate in size to support the flow pattern implied by the feedback explanations of the mechanism of edgetones. The theory is shown to be equivalent to the so‐called acoustical one in which the action at the edge is represented by a dipole whose strength is associated with the fluctuating force sustained by the edge. While the rift between these two approaches to the theory of edgetones may be considered closed, it is to be noted that each may continue to have its special attractions in respect of specific requirements.

ISSN:0001-4966    

DOI:10.1121/1.1909164

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

A printout system has been developed which automatically records any one of over a trillion different quantized analyses of a spoken syllable. The main purpose is research toward improved methods of recognizing speech by machines. However, other applications for the digitized transmission of speech are also indicated. Results of tests made are analyzed and different approaches to the decoding problem are presented.

ISSN:0001-4966    

DOI:10.1121/1.1909165

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

Receivers were presented with equal‐length words under two conditions of difficult reception: (1) by ear, against a background of white noise; and (2) by eye, for a brief period in a tachistoscope. For each word presented, the receiver recorded a message and, immediately following, gave a confidence rating with respect to his accuracy of reception. The similarities between the functions for the auditory and visual modes of reception are marked. It is found that for both auditory and visual presentation the accuracy of reception is (1) directly related to the confidence rating, (2) relatively invariant over a range of signal‐to‐noise ratios, and (3) not impaired by the task of rating. These results support and extend the generality of the statistical decision‐making theory of the receiver.

ISSN:0001-4966    

DOI:10.1121/1.1909166

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

An electrical analog of the nasal cavities has been designed for use in conjunction with a dynamically controllable analog of the vocal tract [G. Rosen, J. Acoust. Soc. Am.30, 201 (1958)]. The acoustical coupling between vocal tract and nasal cavities is electronically variable. Listening tests are conducted to determine the most suitable vocal‐tract configurations for producing nasal consonants in consonant‐vowel and vowel‐consonant syllables. Other listening tests determine the most suitable patterns of temporal variables for these syllables. In general, it is found that more natural‐sounding syllables are obtained when the velopharyngeal coupling varies slowly with time compared to changes in vocal‐tract configuration. The results compare favorably with recent cineradiological data, and are interpreted to support the view that studies with articulatory synthesizers reveal important details about the production and perception of natural speech. The experiments demonstrate that speech can be synthesized from articulatory information in a straightforward and natural manner.

ISSN:0001-4966    

DOI:10.1121/1.1909167

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

The radiation of plane acoustic waves into a medium by composite layered transducers composed of a piezoelectric element and two lossless coupling media is described analytically. The increase in acoustic intensity in the medium receiving the radiation produced by the composite structure over that produced by direct coupling (piezoelectric element in contact with the medium), for the same value of the electric field strength, is considered quantitatively and the results are presented graphically. Composite transducers of the type described can be expected to achieve considerably higher ultrasonic intensities (1000‐fold increase) in both unfocused and focused beams than have heretofore been realized.

ISSN:0001-4966    

DOI:10.1121/1.1909168

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

Temperature and wind data up to altitudes of 200 000 ft have been obtained with meteorological rockets at various locations over North America during the seasons of 1959 and 1960. Seasonal and geographical variations of the atmosphere's acoustical structure, as derived from these data, are illustrated. The thermal and flow effects on the sonic profiles in the lower mesosphere are pointed out. Data in the form of individual cases of interest and seasonal summaries for several locations are presented.

ISSN:0001-4966    

DOI:10.1121/1.1909169

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

Although a majority of auditory fatigue studies have utilized the TTS as the primary index of change in functioning of the auditory system, it is clear that the threshold of audibility is not a completely adequate indication of the auditory system's functional status. Indices of discrimination, for example, are not related in any systematic fashion to the threshold of audibility, since various pathological conditions of the auditory system are reflected differentially in measures of the threshold of audibility and measures of differential thresholds. In the present study changes in the intensity discrimination threshold (IDT) as well as in the threshold of audibility have been determined. Significant decreases in the IDT were found to follow fatiguing exposure, such changes being related in a negatively decelerated manner to the TTS. The extent of the change in the IDT as a function of fatigue was found to be inversely related to the SPL of the signal to be discriminated. As a result of these two relationships the range of IDT's as a function of signal strength was markedly decreased for the fatigued ear. In addition, no relationship was found between normal IDT's and size of the recording pen excursions bracketing the threshold of audibility, or in the change in the size of these two measures as a function of fatigue.

ISSN:0001-4966    

DOI:10.1121/1.1909170

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

This paper describes two experiments which were carried out to evaluate the variability in audiometric procedures. One was designed to evaluate the precision of the audiometric process; the other to determine the repeatability of results in individual subjects taking these examinations. Some differences were found between various instruments used and a learning effect was detected on the part of the subjects. While these differences were not considered large, it was important to determine their magnitude in relation to the study of the effect of noise on hearing.

ISSN:0001-4966    

DOI:10.1121/1.1909172

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

Shifts in the threshold of hearing were determined as a function of prolonged testing (12 sessions) with four experimental groups: forced‐choice‐feedback, no‐forced‐choice‐feedback, forced‐choice‐no‐feedback, and no‐forced‐choice‐no‐feedback. The forced‐choice technique was found to improve performance if used with immediate knowledge of results (feedback). Otherwise, thresholds obtained under a forced‐choice procedure were poorer than those obtained under no‐forced‐choice instructions. Even after 12 sessions, increasing the subjects' motivation by offers of monetary rewards resulted in a further decrease in threshold.

ISSN:0001-4966    

DOI:10.1121/1.1909173

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

The loudness of three‐tone complexes centered at 2000 cps was studied as a function of the intensity relations among the three components. Two types of spectra were investigated: (1) peaked spectra, in which the intensity difference between the middle component and the less intense side bands was varied from 0 to 35 rib, and (2) sloped spectra, in which the slope of the connected heights of the three spectral lines of the complex was varied from 0 db per octave to + and −∞. Generally, three‐tone complex whose over‐all spacing was greater than a critical band was loudest, at a given SPL ,when its spectrum was flat, i.e., when the components were equally intense and, more important, equally loud. Complexes whose over‐all spacing was slightly less than a critical band changed little in loudness as a function of spectrum shape. The results are related to the assumption that the loudness of a complex sound is the sum of the loudnesses of the component critical bands.

ISSN:0001-4966    

DOI:10.1121/1.1909174

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP