摘要:

Intense auditory stimuli (combinations of “noise and music”) are being used to some extent in dentistry and medicine for their analgesic effects. Maximum‐exposure durations and intensities of noise and music are specified to avoid any undue amount of auditory fatigue. These specifications are based upon previous damage‐risk criteria and research data appearing in the literature on this subject and upon the findings of a series of experiments in which the hearing of subjects was tested before and after exposure to noise and music. The results of these new experiments are compared with the calculations made with formulas developed by Ward, Glorig, and Sklar for predicting the auditory fatigue from exposure to noise. The predicted and obtained results are in very close agreement.

ISSN:0001-4966    

DOI:10.1121/1.1918138

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

An investigation of the temporal delays associated with internal‐sidetone pathways was undertaken. The results showed delay to be a function of frequency for impulsive signals transmitted from the incisors to the mastoid process by bone and from the thyroid cartilage to the mastoid process by tissue. A similar finding was obtained for phonated signals transmitted from the vocal cords to the mastoid process by the internal sidetone pathways of minimum delay irrespective of media.

ISSN:0001-4966    

DOI:10.1121/1.1918139

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

Two alternate methods for the selection of speech material to be used in studies in automatic speech recognition are suggested. Preference is given to the selection of a restricted set of phonemes from which words and sentences may be constructed for analysis. The selection can be based on the high frequency of occurrence of the individual phonemes, on the high yield of words by the phonemes, or on some combination of these two criteria. A combination of the two criteria appears to be most satisfactory. The phoneme selection was derived from the 500 most frequently occurring words, as given by Thorndike and Lorge. Some consideration was also given to the frequencies of occurrence of the phonemes. The phonemes are presented in cumulative order according to the number of words by which the list is increased as each successive phoneme is added.

ISSN:0001-4966    

DOI:10.1121/1.1918140

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

Apparatus for measuring ultrasonic wave velocities and hence elastic moduli by means of phase‐comparison methods at frequencies as high as 500 Mc is described. Gated harmonic generators for providing pulse‐modulated rf of accurately known carrier frequency and circuits for electrical coupling to resonant quartz‐crystal transducers are discussed. Application to measurements on small specimens, with illustrative data for cadmium telluride, is made.

ISSN:0001-4966    

DOI:10.1121/1.1918141

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

The rate at which harmonics are developed during the propagation of an initially sinusoidal ultrasonic wave of finite amplitude depends on the nonlinearity of the compressibility of the medium. Thus, determinations of the harmonics as a function of propagation distance may be used to determine the parameterB/A(describing nonlinearity). A method which circumvents the effects of absorption in the medium is developed and used to determine the parameterB/Afor water andm‐xylene. This method utilizes optical determinations of the second harmonic component of a distorted 3.0 Mc ultrasonic wave at various distances and initial pressure amplitudes. The second harmonic was isolated by use of a calibrated acoustic filter plate. The values obtained for the nonlinearity parameter areB/A = 6.2±0.6for water andB/A = 9.6±1form‐xylene.

ISSN:0001-4966    

DOI:10.1121/1.1918142

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

Irradiation of strain‐free methacrylate with a single beam of focused ultrasound in adequate dosages results in the development of trackless focal alterations within the plastic. These alterations, easily visualized with polarized light, are egg‐shaped regions of stress and are probably thermal in origin. There is a consistent and reproducible relationship between ultrasonic dosage and the size of these “lesions,” comparable to that obtained when the brain of the cat is similarly irradiated. The use of methacrylate as a preliminary test medium permits rapid evaluation of the probable effects of varying dosage parameters as well as of the repetitive (and long term) stability of the ultrasonic output.

ISSN:0001-4966    

DOI:10.1121/1.1918143

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

A method is described for formulating an exact solution to any problem involving an elastic cylindrical bar with a free lateral surface and mixed time‐dependent end conditions. To illustrate the method and to test the practicality of simulating pure end conditions by conditions given in mixed form, a solution is obtained for a particular problem involving both longitudinal and flexural strain. Asymptotic expressions valid at large distances from the end of the bar or for long times after the load is applied are developed for the integrals of the exact solution to the particular problem and predictions based on these expressions are compared with results of an experimental test in which pure end conditions were used. In this case and for large distances or long times, all of the main features of the observed behavior were correctly predicted.

ISSN:0001-4966    

DOI:10.1121/1.1918144

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

An approximate theory of symmetric vibrations of elastic rods is used to develop frequency equations governing the vibrations of finite rods. The roots of these equations are used to form frequency spectra that predict the lower resonant frequencies of axially symmetric motions of a circular, elastic rod of given length.

ISSN:0001-4966    

DOI:10.1121/1.1918145

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

The general linearized equations governing the propagation of sound in a dissipationless temperature‐ and wind‐stratified medium are derived. A formal integral expression is given for the field of a point source located in such a medium, when it is bounded by an absorbing plane under conditions which lead to the formation of a shadow zone. This integral yields the following approximate (high‐frequency) expression for the decay rate within the shadow|p|2 = (B/r) exp[−(n/c)f13(−c′−U′ cosφ)23r]. Herepis the acoustic pressure,ris radial distance from the source,Bis independent ofr, fis frequency in cps,cis sound speed,c′ andU′ are sound‐ and wind‐speed gradients at the ground surface, φ is the angle between the wind direction and the direction of sound propagation, andnis equal to 5.93 for a pressure release boundary and to 2.58 for a hard boundary.

ISSN:0001-4966    

DOI:10.1121/1.1918146

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

Longitudinal and flexural waves in an infinite plate of an isotropic elastic material can be analytically synthesized from a single dilatational potential function and a single rotational potential function. IfAis the amplitude of the former andBis the amplitude of the latter, it is possible to calculate the ratioA/Bfor a particular mode as a function of frequency once the values of the roots of the appropriate frequency equation are at hand. Calculations of this kind have been carried out for the lowest three longitudinal and lowest three flexural modes and show that, in general, these modes are composite wave motions involving varying combinations of dilatational and rotational components such thatA/Bvaries in amplitude and phase in a given mode as a function of frequency. The primary purpose of this paper is to introduce the “character” of the various modes, defined as [(A/B)(A/B)*], as a concept useful in understanding the selective attenuation of high‐frequency elastic modes in polycrystalline metal strips. In this type of medium, rotational waves are attenuated appreciably more than dilatational waves; hence a given mode might be expected to exist more strongly over the frequency range in which the total wave motion is predominantly dilatational in character. Measurements of the attenuation of elastic pulses having 5 to 35 Mc carrier frequencies and traveling in thin strips of polycrystalline aluminum have been made. In the results, a good correlation is observed between the frequency range over which a given mode is observed and the frequency range over which, theoretically, the character of the mode is large; i.e., [(A/B)(A/B)*]>1.

ISSN:0001-4966    

DOI:10.1121/1.1918147

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP