摘要:

This paper presents the results of a theoretical study of the effects of water loading on a turbulent‐flow‐excited, thin, finite plate. The water loading is defined as the pressure field produced in the water, at the plate surface, as a result of the plate vibration. The propagating component of this pressure field acts in temporal phase with plate resistive forces, and the nonpropagating component acts in phase with plate inertial forces. Thus, water loading may be interpreted as additional inertia and additional resistance of the plate. In an example, comparison of computed, turbulent‐flow‐excited water loaded and in‐vacuo plate vibration spectra revealed the additional inertia to be 1.5–12 times the inertia of the plate alone. The additional resistance was found to be approximately 1% of the critical value of the in‐vacuo plate. The additional inertial and resistive forces caused the “mode” shapes of the water‐loaded plate to differ from the corresponding mode shapes of the in‐vacuo plate.

ISSN:0001-4966    

DOI:10.1121/1.1981625

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

A fundamental operational solution of lossless Burgers' equation is used as the basis for deriving the spectrum of a two‐frequency finite‐amplitude source within the critical range. The resulting expression is then generalized to the case of a multiple‐frequency finite‐amplitude source. The region of validity of these solutions is determined by specifying the critical ranges at which the waveforms become multivalued.

ISSN:0001-4966    

DOI:10.1121/1.1981632

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

The absorption coefficient and velocity of ultrasound at 19 MHz were studied as a function of concentration in binary solutions of pyridine with water, methanol, and ethanol. In addition, the compressibility and Rao's and Wada's constants were calculated and studied as a function of concentration. The measurements were made at 15°, 25°, and 35°C. An attempt was made to relate the concentration dependence of the absorption coefficient and the velocity to several reaction mechanisms—molecular association, deactivation of vibrational energy levels in pyridine, and perhaps others. In this attempt density, viscosity, and vapor pressure data from the literature were used along with the measured ultrasonic data.

ISSN:0001-4966    

DOI:10.1121/1.1981642

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

The adiabatic elastic stiffness moduli of a 22‐carat type II diamond have been measured at 25.0°C by the ultrasonic technique described in IEEE Trans. Sonics Ultrasonics SU‐5, 25 (1957). Basic wave velocities were obtained over a frequency range 20–500 MHz in order to minimize errors due to diffraction and coupling effects. Variations with hydrostatic pressure were measured at 20 MHz using a pulse superposition technique [J. Acoust. Soc. Amer.41, 1052 (1967)]. Values of moduli in units of 1012dyn/cm2and their respective pressure derivatives (dc/dP) are as follows:c11 = 10.79±0.05;c12 = 1.24±0.05;c44 = 5.78±0.02, 5.98±0.7, 3.06±0.7, and2.98±0.3.

ISSN:0001-4966    

DOI:10.1121/1.1981645

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

A new technique for calculating the natural frequencies of composite shells was developed. The technique is based upon the finite element method of structural analysis and Rayleigh's principle, which is applied directly to shell structures for the first time. Because the element developed is applicable to anisotropic shells of arbitrary shape, the technique is very general. By using Rayleigh's principle the necessity of assembling over all mass and stiffness matrices for the structure and solving the resulting characteristic equation is eliminated; frequencies are calculated using elemental mass and stiffness matrices directly. Thus the technique is very efficient from a computational standpoint. It is made even more efficient by using a special mass matrix which is a hybrid between a lumped and a distributed mass matrix. Another unique feature is that prior information regarding the modal vectors can be used directly to decrease the computational time.

ISSN:0001-4966    

DOI:10.1121/1.1981652

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

An analytical method of predicting the mode shapes and natural frequencies of vibration for continuous structures with elastic edge constraints is presented. The method consists of formulating dynamic edge receptances for the structure using classical solution techniques and matching the receptance of the structure with the receptance of the constraining boundary. The technique is illustrated by the solution of a beam and a circular plate with elastic boundaries and with boundary damping. A discussion is presented giving the influence of the boundary conditions on the vibration of the structure. These examples show numerically the effect of elasticity of the support on the resonant frequencies and mode shapes of the structure. Parameters are obtained which indicate when one may assume simply supported or clamped boundaries for the actual case of elastic boundaries without introducing large errors in the natural frequency or mode shape.

ISSN:0001-4966    

DOI:10.1121/1.1981656

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

The response of two simple systems, such as beams or plates, strongly coupled at a point is discussed. Two models of a mass, spring and gyroscopic coupling mechanism are treated. It is shown that the SEA power flow‐energy difference result can be obtained even when the coupling is strong. For one model of the coupling mechanism, the power flow can be expressed in terms of changes in modal resonance frequencies caused by the coupling.

ISSN:0001-4966    

DOI:10.1121/1.1981679

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

Both the traditional vowel triangle and more recent schemes of vowel classification present us with a picture in which the members of at least three pairs of vowels, /i‐I/, /e‐ɛ/, and u‐U/, are said to be differentiated from each other by a feature of tenseness. It has been suggested that differences in tension between the members of a tense‐lax pair of vowels are manifested in the extrinsic muscles of the tongue. In the experiment reported here, electromyographic potentials for the genioglossus muscle were investigated to determine the extent, if any, of tension differences between the members of the pairs of vowels listed above. It was found that the posited differences in tension do exist, although the findings cast some doubt on traditionally proposed height relationships for the front series of vowels, /i‐I‐e‐ɛ/. Electromyographic potentials of muscles associated with jaw opening and tongue backing were investigated to see if the genioglossus data could be reconciled with the usual height ordering of the front vowels. Results indicate that there is reason to believe the height ordering of these vowels generally presented in the literature is correct.

ISSN:0001-4966    

DOI:10.1121/1.1981689

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

The observations reported in this paper pertain to the articulatory movements—especially tongue movements—that are associated with the American English diphthongs /al/, /ɔI/, and /aU/. Flesh points on the lingual surface were simulated by attaching small radiopaque markers to the midline of the tongue body. Lateral‐view cinefluorography was used to record the displacement patterns of these markers during the production of diphthongs in isolated words and short sentences. Data were collected for three speech samples, each of which was read by a different set of two speakers. Consideration of these data emphasizes the general problem of identifying invariant phonemic correlates at the articulatory level, with illustrations of the variability in (1) the initial and terminal vocal‐tract configurations for a given diphthong, (2) the patterns of tongue‐point movement for a given diphthong, and (3) the tongue‐point velocities during a given diphthong. [Research supported in part by grants from NIH.]

ISSN:0001-4966    

DOI:10.1121/1.1981694

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

Naturally produced interaural differences of time and intensity rarely occur alone, but rather are present in different amounts depending on the shape and size of the animal's head and pinnae and on the acoustic frequency of the stimulus. This study was designed to explore that problem by examination of differences in the neural responses to sounds presented to animals from different locations in free‐field space. Stimuli were tone bursts (500–5250 Hz), present in an anechoic chamber from speakers arranged in a semicircle around the animal's head. Minimum resolution was 20°. Frequency characteristics of the speakers were compensated for by a computer‐controlled attenuator. Animals were held by a specially designed headholder on which all support members are placed well behind their heads. Extracellular microelectrode recordings were obtained from cells in the inferior colliculus of barbiturate anesthetized cats. Responses of these cells to auditory direction were varied, but it appears that the dominant type of direction sensitive cell shows an initial response which carries information about the presence of sound, with a later discharge that carries information about direction

ISSN:0001-4966    

DOI:10.1121/1.1981700

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP