摘要:

The generation of nasal consonants can be simulated approximately by a cascade connection of simple electrical tuned circuits excited by a quasi‐periodic electrical buzz source. The lowest resonance for nasal consonants is in the vicinity of 200 to 300 cps, and the damping of this resonance is greater than that for the first resonance of vowels. A terminal‐analog synthesizer and control device have been used to generate a number of synthetic syllables, each consisting of a nasal consonant followed by a vowel, with smooth formant transitions between consonant and vowel portions. Systematic listening tests have shown that the identification of the nasal consonant is determined largely by the frequency position of the second resonance of the nasal portion of the syllable, and thus by the direction and extent of the second formant transition of the vowel, as noted in other studies. The identification of the nasal consonant is also dependent to some extent on the duration of the consonant and transition portions of the syllable. Isolated nasal consonants generated by this procedure can also be identified with reasonable consistency.

ISSN:0001-4966    

DOI:10.1121/1.1907770

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

The shape of the vocal cord wave is an important parameter in a true analog representation of the vocal mechanism, since the final speech wave is a function of both the generator wave shape and the transfer impedance of the vocal tract. The shape of this wave has been determined by two independent methods: (1) by the derivation and use of a network having a characteristic which is the inverse of the first vocal resonance, and (2) by measuring the area of the vocal cord opening as a function of time through the use of motion picture studies. Harmonic analysis of some of the typical shapes obtained indicate that a uniform distribution of harmonic amplitudes is a rarity; instead there is a tendency for the distribution to have a cyclical variation of the form (sinkn/kn2). The results obtained through the use of the inverse network indicate that the main excitation of the higher resonances occurs at the point of vocal cord closure and that the magnitude of this excitation can be controlled by the talker over wide ranges.

ISSN:0001-4966    

DOI:10.1121/1.1907771

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

The author is working towards the development of an ultrasonic viewing system which is an analog in ultrasound of conventional light photography. In the present paper it is shown that a sonic lens is able to resolve two sources of ultrasound whose spacing is about equal to the length of one wave of the sonic energy in use. It is also shown that at the frequency being used (3 Mc) uniform illumination of an object for sonic viewing is very difficult because Fresnel near field and other diffraction and interference effects occur very readily and that these effects are frequently themselves not stable.

ISSN:0001-4966    

DOI:10.1121/1.1907772

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

The molecular basis for ultrasonic absorption in liquids is reviewed. The various loss mechanisms are all relaxation processes which include such phenomena as vibrational, isomeric, structural and shear relaxation effects. The relation between such factors as the relaxation time and the properties of the liquid are considered.

ISSN:0001-4966    

DOI:10.1121/1.1907773

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

The problem of propagation of traveling waves in a right circular cylinder having hexagonal elastic symmetry is considered here. Exact expressions for the displacements produced by both the compressional and torsional modes are obtained. A conclusion of importance in ultrasonic methods is the result that the compressional and torsional modes propagate independently without coupling either through the equations of motion or the boundary conditions. A condition relating the frequency and wave number of the torsional wave is derived.

ISSN:0001-4966    

DOI:10.1121/1.1907774

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

A general method is developed for the solution of the linearized equations of elasticity for both homogeneous and inhomogeneous media. This method yields solutions which describe propagating waves which may be pulses, rapidly changing wave forms, or periodic waves. It is not restricted by the usual considerations which depend upon separation of variables. The solution consists of a series of terms, the first of which describes the wave motion predicted by geometrical optics. Subsequent terms account for certain types of diffraction effects. The series is not necessarily convergent but is presumably asymptotic to the solution.

ISSN:0001-4966    

DOI:10.1121/1.1907775

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

Special arrangements are used to produce small‐scale eddying near surfaces at which reactions are taking place. Experiments in which the reaction involves a photographic emulsion acted upon by developer show that the development process is considerably accelerated in small areas where the near‐surface flow is concentrated. Resonant gas bubbles appear to be by far the most efficient sources of sonically induced micro‐eddying. When such a bubble rests on an emulsion surface the development reaction in its neighborhood is significantly affected, evidently because of the local “microstirring,” at ambient pressure amplitudes much less than are typically used in sonic and ultrasonic applications. Sonic microstreaming, especially as induced near resonant bubbles at boundaries, appears to be an important mechanism in accounting for certain well‐known effects of ultrasound. Continued development may lead to means for applying microstreaming to surface processes in a controlled and specifiable manner.

ISSN:0001-4966    

DOI:10.1121/1.1907776

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

The operation of the human heart together with the sounds resulting from normal operation are discussed. Examples of the diagnostic, intracardiac sounds due to several of the common congenital lesions are cited and analyzed. Transmission and magnitude of heart sounds within the heart have been measured and are reported.

ISSN:0001-4966    

DOI:10.1121/1.1907777

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

The attenuation of sound propagated out‐of‐doors is conveniently separated into attenuation due to spherical divergence and excess attenuation due to atmospheric and terrain effects. This excess attenuation is principally caused by sound absorption in the air, the refractive effects of temperature and wind gradients, by turbulence and the effects of terrain and ground cover. To investigate these effects the propagation of sound over open, level ground, through dense evergreen forests, and between hilltops was studied experimentally in the frequency range between about 300 cps and 5000 cps. Extensive micrometeorological instrumentation was utilized to measure and record the relevant micrometeorological parameters simultaneously with the acoustic data for a wide variety of weather conditions. Data on the attenuation of the mean received sound pressure level as well as on the fluctuations about the mean were obtained and correlated with the state of the atmosphere.Over open level terrain, the excess attenuation upwind was found to exceed that for downwind propagation by as much as 25–30 db for source and receiver heights of 12 and 5 ft, respectively. Temperature and wind gradients near the ground‐air interface largely account for this difference. In hilltop‐to‐hilltop propagation, wind direction is of secondary importance, and in dense woods absorption and scattering control. Empirical functions were derived for the purpose of estimating the mean excess attenuation as a function of frequency and distance, for a given set of micrometeorological conditions. These charts have been found useful in many practical problems involving the propagation of sound over open level ground.

ISSN:0001-4966    

DOI:10.1121/1.1907778

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

Exact general solutions of the three‐dimensional elasticity equations of motion in polar cylindrical coordinates are obtained for axisymmetric and antisymmetric thickness‐shear vibrations. These solutions are applied in solving five solid and hollow circular bar problems. Natural frequencies are tabulated.

ISSN:0001-4966    

DOI:10.1121/1.1907779

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP