摘要:

A simple theory of three forms of holographic interferometry “time‐average,” multiple‐exposure, and “real‐time” (live) interferometry is presented, based on a new development in holographic “image synthesis” (complex amplitude addition and subtraction), introduced in 1965 by D. Gabor and G. W. Strokeet al.They demonstrated the remarkable property of holography: Interference can occur between two or more light beams that are not superimposed either in time or in space, if the holographic intensities corresponding to the beams are obtained with the aid of a coherent reference‐background beam of the same spatial shape and if these intensities are successively added in the same hologram. Following the independent discovery of holographic interferometry, in 1965, by J. M. Burch; by R. L. Powell and K. A. Stetson; and by L. O. Heflinger, R. F. Wuerker, and R. E. Brooks, among others, it was found that two or more successive photographic additions of the hologram intensities (corresponding to two or moresequentialpositions or shapes of a given object) would thus indeed permit one to “synthesize,” in the form of an interferogram, the complex sum of the spatial‐electric‐field vectors, corresponding to each object‐point position, as if the different object‐point positions had all existedsimultaneouslyrather than sequentially, as they do during the hologram recording (for instance in the case of multiple holographic‐image recording of a vibrating object). The rigorous equations we present, notably in vector form, for the general cases of practical interest bear out the equations previously derived by a number of authors, for some special cases, frequently in heuristic form.

ISSN:0001-4966    

DOI:10.1121/1.1911587

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Three mel scales, derived from fractionation data, and representing three differential noise conditions are obtained. It is found upon comparison that the presently found no‐noise function differs in no essential manner from the generally accepted mel scale advanced by Stevens (1940). However, upon the introduction of a wide‐band masker, the shape of the mel function becomes more positively accelerated. In general, when holding the intensity of the masker constant, this acceleration is inversely related to the sensation level of the experimental tones above masked threshold, and is not frequency dependent. Although this relationship is not dependent upon frequency per se, the magnitude of pitch shift increases with frequency.

ISSN:0001-4966    

DOI:10.1121/1.1911588

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

This investigation was designed to obtain the monaural loudness function for a 1000‐Hz tone. Ten trained observers with normal hearing were utilized. The method used was the numerical magnitude balance procedure. This investigation indicates that the results obtained by the numerical magnitude balance procedure are repeatable if the observers do not have previous knowledge of the decibel scale, and if they are properly trained. This is indicated by the good agreement of the results of this study with the findings of previous studies. The results of this study showed a loudness exponent of 0.54 based on data averaged by geometric means and 0.51 based on data averaged by medians.

ISSN:0001-4966    

DOI:10.1121/1.1911589

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

The over‐all loudness of a pair of equally loud tones presented dichotically, a different frequency to each ear, is independent of the frequency separation between the two tones. This rule applies over the whole range of frequency separations tested, from 0 Hz to several thousand hertz; hence, dichotic tone pairs are just as loud as a binaural pair (same frequency to each ear). Both binaural and dichotic pairs, however, are generally less than twice as loud as a component presented by itself. The over‐all loudness is invariant even though at narrow frequency separations the components of a dichotic pair interfere with each other so that each component is softer when heard in the presence of the other than when heard by itself. At wide separations, where two distinct auditory images are reported, the loudness of a component is the same whether presented with or without the contralateral tone.

ISSN:0001-4966    

DOI:10.1121/1.1911590

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Threshold measurements were obtained for low‐pass‐ and high‐pass‐filtered noises in the presence of pure tones in normal subjects. High‐pass‐filtered noise with cutoff frequencies at 2400 Hz and above yielded masking peaks near the cutoff frequencies. When noise was filtered with cutoff frequencies at 1200 Hz and below, pure tones of 800 and 1000 Hz had the greatest masking effect. For low‐pass‐filtered noise, as the bandwidth increased, masking peaks moved from low frequency to high. The masking effect was indistinguishable from that of white noise when filtered noise was cutoff at frequencies of 2400 Hz and above. These results suggest that there is a definite mechanical resonant frequency effect on noise when the width of filtered noise exceeds a critical value. Masking effects are discussed in relationship to mechanical resonant frequency and the interaction of difference and summation tones.

ISSN:0001-4966    

DOI:10.1121/1.1911591

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

An assessment of the suitability of ferrofluids for acoustic transducer and receiver applications has led to the following conclusions:First, the magnetostrictive mode of operation is not efficient enough to offer an alternative to conventional solid materials in use.Second, the piston motion of the ferrofluid induced by an applied field gradient does provide a real alternative to conventional magnetostrictive transducers. For an applied static field of 4000 Oe and a field gradient of 1000 Oe/cm, it is possible to achieve an overall efficiency that is greater than that for the ferromagnetic solids.Third, ferrofluids appear to provide a desirable alternative for pressure‐sensing applications in severe environments (e.g., detonations) where piezoelectric and pyroelectric materials suffer fatigue and failure.Fourth, ferrofluids offer the prospect of obtaining broadband frequency response when radiating or receiving in liquid media.

ISSN:0001-4966    

DOI:10.1121/1.1911592

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

This study was an attempt to account for the motor control of speech production by a model in which discrete phoneme commands are modified according to phonological context by three motor system mechanisms. The model was evaluated by consideration of high‐speed cinelluorograms, and electromyograms from nine articulatory locations, recorded while one subject produced 36 consonant‐vowel consonant monosyllables. The syllables were formed by every possible combination of initial and final consonants /b/, /d/, and /g/, and the syllable nuclei /i/, /u/, /æ/, and /ɔ/. In every possible case, some aspect of the motor control of a later syllable component was influenced by the identity of the previous one. Except in a few cases, some aspect of the motor control of an earlier syllable component was influenced by the identity of the following one. These latter influences were of greater magnitude and complexity, and more reflected in movement, in the initial consonant than in the vowel. Some of the context effects on phonemes could be accounted for by the three motor system mechanisms but a number could not. The results suggested that syllabic factors are influential in the “premotor” command structure of speech, and, in particular, that the CV form is a relatively cohesive component of CVC syllables.

ISSN:0001-4966    

DOI:10.1121/1.1911593

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Pulse propagation in a thermally relaxing liquid is studied theoretically.First, Whitham's theory of wave propagation in systems governed by more than one velocity is utilized to obtain qualitative information.Second, Laplace transform solutions are obtained for particle velocity and pressure for rectangular and Gaussian pulses as well as semi‐infinite sine wave. Detailed numerical calculations are included.

ISSN:0001-4966    

DOI:10.1121/1.1911594

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

The elastic wave propagations in deformed crystals with any symmetry are investigated theoretically. The rotationless acoustical tensor, which specifies the propagation condition, consists of the tensor based on the natural unstressed state and the perturbation term being proportional to the stress. The perturbation theory is applied to nondegenerate and degenerate cases with respect to the quasitransverse wave velocities. The perturbed wave velocities and the polarization directions are formulated by the stress suppressed on the crystals, and then the general formulas for the acoustical birefringence depending on the second‐ and third‐order elastic constants are reduced. The difference of the quasitransverse wave velocities is expressed by the sum of two terms: the difference of these in unstressed crystals due to the intrinsic anisotropy and the perturbation term due to the stress. In the cases of the cubic system and of the isotropic material, the explicit relations are calculated. For the isotropic material, the so‐called stress‐acoustical law holds.

ISSN:0001-4966    

DOI:10.1121/1.1911595

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

The presence of evanescent ultrasonic waves diffracted from an acoustic grating has been detected using Bragg diffraction of laser light. The diffraction of light by these evanescent waves (whose concept stems originally from theoretical arguments) confirms their physical existence. The grating used was designed to diffract the sound into two kinds of wave components: (1) a single propagating wave component moving directly away from the grating; and (2) a pair of oppositely directed evanescent‐wave components traveling along the back surface of the grating and forming a standing evanescent wave with exponential decay perpendicular to the grating. Such evanescent waves have shorter wavelengths than propagating waves and hence are inherently capable of better resolution if used for imaging. With the proper orientation of the laser beam with respect to the grating, theory predicts that the above wave components will produce diffracted spots of light symmetrically placed about a central axis. The spots due to the evanescent‐wave components are found on an axis perpendicular to that of the spots due to the propagating‐wave component, and the evanescent‐wave spots are further away from the center. Detection and measurement of the positions and the relative intensities of the spots gives information about the wavelengths of the components and about the rate of exponential decay of the evanescent wave.

ISSN:0001-4966    

DOI:10.1121/1.1911596

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP