摘要:

Listeners' recognition of wind‐instrument tones was investigated for the tone concert F on the treble staff (frequency approximately 349 cps). Tones of a flute, oboe, B‐flat clarinet, tenor saxophone, alto saxophone, cornet, trumpet, French horn, trombone, and baritone were recorded, equated for duration and sound level as well as frequency. Thirty university band members listened to these tones played back: unaltered, backward, with the rise and decay removed, and through a 480‐cps low‐pass filter. Recognition of wind‐instrument tone quality was best for the unaltered playback, next best under the backward condition, next in the absence of rise and decay, and poorest under the filtered condition.

ISSN:0001-4966    

DOI:10.1121/1.1919287

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

The pitch‐excited vocoder invented by Dudley can be greatly improved and, it appears, made to produce very natural speech by the inclusion of (a) very precise pitch extraction and buzz‐hiss indication, (b) pre‐modulation spectral flattening of the exciting signal, and (c) more speechlike phase. This paper outlines a technique that induces more speechlike phase in a spectrally flattened pitch‐excited vocoder. Results obtained thus far from a computer‐simulated vocoder are quite hopeful.

ISSN:0001-4966    

DOI:10.1121/1.1919288

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

The purpose of this study is to evaluate the channel capacity necessary to transmit pitch‐period duration values. Using a statistical approach, the average uncertainty (entropy) of a pitch‐period duration value was calculated, taking into account knowledge about the just‐preceding pitch‐period duration value. The data consisted of utterances from 26 speakers (13 male and 13 female); a total of 12 576 pitch‐period duration values was obtained. The results show that, for pitch‐period duration values quantized within 50 μsec, the theoretical channel capacity is 621 bit/sec, for the case where conditioning extends one duration value into the past.

ISSN:0001-4966    

DOI:10.1121/1.1919289

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

An experimental, digitized channel vocoder has been designed and built at the Lincoln Laboratory. This vocoder differs from previous vocoders in the design of the pitch extractor. Pitch is obtained by using a special‐purpose digital computer to combine the outputs of 6 analog pitch indicators. The synthesizer uses spectral flattening to reduce spectral distortion caused by pitch variations and nonuniform filter bandwidths. For high‐quality speech input, the quality of the Lincoln vocoder is considered by many listeners to be comparable to that of a voice‐excited vocoder.

ISSN:0001-4966    

DOI:10.1121/1.1919290

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

The possibility of employing a time‐varying refractive‐index gradient, generated by an ultrasonic standing wave in solids and liquids, to provide nonmechanical optical‐beam scanning has been investigated in detail. Heretofore‐unobtained deflections of sufficiently large angles to be of practical value in active optical systems have been achieved. These angles range between 3° and 6° at frequencies below and above 200 kc/sec. respectively. Standard slit and photomultiplier techniques were employed to study the effects of stress‐induced birefringence in crystal quartz on the attainable angular movement of two collinearly deflected light beams that were orthogonally plane polarized. High‐speed streak photography was used to measure the fidelity of the light beam as it emerged from a tetrachloroethylene ultrasonic cell. The photographic technique was utilized to evaluate effects of (1) light‐beam diameter/sonic‐wavelength ratio, (2) light‐beam transit position relative to the sonic‐pressure nodal point, and (3) light‐beam angular‐deflection amplitude.

ISSN:0001-4966    

DOI:10.1121/1.1919291

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

An ultrasonic absorption cell has been constructed that maintains parallelism sufficient for absorption measurements well above 500 Mc/sec. Constructional details are described and results presented showing absorption in benzene, dioxane, and polysiloxane at 510 Mc/sec. The system as a whole will permit an attenuation of about 35 dB before the signal is lost in the noise. The absorption in benzene divided by the square of the frequency is substantially lower than values obtained at low frequencies, and indicates a relaxation frequency of approximately 600 Mc/sec.

ISSN:0001-4966    

DOI:10.1121/1.1919292

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

Velocity of sound measurements have been made in superheated steam at pressures from 200 to 1000 lb/in.2and over a range of temperatures from 395° to 750°F. Experimental values are in agreement with calculated values, using existing Tables on the thermodynamic properties of steam. A variable path‐type acoustic interferometer of stainless and chrome‐alloy steel was used for the present work. Frequency range was from 650 to 1000 kc/sec.

ISSN:0001-4966    

DOI:10.1121/1.1919293

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

This paper presents the theory and first experimental observations with a new method for accurately standardizing the amplitude of small mechanical oscillations in terms of an optical wavelength. A multiple beam interferometer of the Fizeau type is used in which a simple harmonic motion of known frequency is imparted to one of the surfaces of the interferometer. The oscillating multiple‐beam fringe pattern is viewed with a photoelectric detector through a slit aperture arranged parallel to the fringes. The resultant photoelectric current contains harmonics of the frequency of oscillation and a strong one is selected by tuning a detector. The amplitude of the selected harmonic is shown by analysis to depend on only three variables: (1) the aperture widthRrelative to a fringe spacing, (2) the geometric mean reflectancerof the two silvered surfaces of the interferometer, and (3) the peak amplitude of oscillation of the fringe patternn0fringe spacings. A functionH(R,r,n0) is calculated as a function ofn0for certain values ofRandrand it is shown to have a large number of prominent turning points. With the exception of the first, these turning points form a series with a common interval of one fringe spacing. The calculated values of the positions of the turning points are independent ofRandrwithin ranges of variation ofRandrrepresenting realistic estimates of errors likely to occur in the values of these quantities. Experiments have shown that, provided that the center of oscillation of the interferometer is stable, the form of the relationship and, more important, the positions of the turning points can be satisfactorily reproduced. The range of amplitudes that the method is potentially capable of standardizing is at present considered to be 0.25 to 10 μ, the precise values depending on the wavelength used.

ISSN:0001-4966    

DOI:10.1121/1.1919294

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

In the present paper, the equations of elasticity and equations of electricity, together with the constitutive relations of a piezoelectric quartz, have been used to solve the problem set forth in the title.

ISSN:0001-4966    

DOI:10.1121/1.1919295

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

Approximate equations are used to study the thermoelastic dissipation present in the thickness shear and flexural vibrations of a finiteAT‐cut quartz plate with tractionfree edges. The dimensionless measure of energy dissipationQ−1is found to be of the order of 10−8near the thickness shear frequency.

ISSN:0001-4966    

DOI:10.1121/1.1919296

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP