摘要:

We describe in this paper a method of decomposing a speech wave into a number ofelementary signalsrepresenting the contribution of the individual vocal‐tract resonances. The decomposition is achieved by filtering out all but the desired resonance component from the speech wave on the basis of a suitably defined criterion of smoothness. The method assumes that the waveforms of the individual resonances can be distinguished according to the smoothness criterion. The parameters of the filter vary with time according to the changing character of the vocal tract resonances. Typically, the filter coefficients are adjusted once every pitch period. The number of filter coefficients equals the number of complex resonances of the vocal tract. In addition to excitation parameters, each elementary signal is described by four parameters representing the frequency, amplitude, bandwidth, and phase of a particular formant. The method provides an automatic method of extracting formant parameters for speech recognition and synthesis.

ISSN:0001-4966    

DOI:10.1121/1.2003960

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

In this paper we will describe the portion of the text‐to‐speech conversion system which accepts a phonetic transcription, stress, and timing information as its input, and outputs the corresponding speech wave. The synthesis program is a form of dyadic concatenation of LPC area segments obtained from natural speech; in addition, the program also calculates the amplitude and intonation. The dyadic concatenation is performed using a matrix of phoneme transitions to obtain the LPC area parameters; the amplitude is obtained by rules which depend on the class of the phonemes involved in the amplitude computation. The fundamental frequency contour is obtained by an adjustment of a stored fundamental frequency contour to fit the utterance to be synthesized. This adjustment is performed by selecting the portion of the stored fundamental frequency contour which fits the number of words and their function in the utterance. The location of the peak of the contour for each word in the utterance is then adjusted to fall at the location of the primary stress.

ISSN:0001-4966    

DOI:10.1121/1.2003967

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Several recent studies have focused on the degree to which acoustic scattering from wind driven water surfaces exhibits frequency spreading which is asymmetric in any regular way. Ocean experiments, physical model studies and analytical models have so far not been entirely in agreement on this issue. Therefore a set of physical model experiments has been performed to investigate the sensitivity of frequency spreading asymmetries to variations in geometric parameters. These experiments were conducted using broadband probing signals in the model tank at Yale. Grazing angle, azimuth, projector and receiver beam pattern, acoustic frequency, and surface roughness were varied in a systematic way. The results of this series indicate that frequency spreading is in fact quite sensitive to a number of geometric parameters and that most current analytical models are inadequate to explain the detailed behavior of this phenomenon. [Work supported by NSF and Code 320, Naval Electronic Systems Command.]

ISSN:0001-4966    

DOI:10.1121/1.2003972

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Radiation from merchant shipping is the most important cause of low‐frequency underwater ambient noise. Predictions of noise properties thus requires an understanding of the radiation characteristics—source level and directionality—of merchant ships. Since the adequate measurement and diagnosis of such properties of a full scale ship is very expensive, a 1:100 scale model of a typical 600 ft tanker was fabricated. The level of structural detail retained in the model was consistant with the frequency regime of interest, 5–50 Hz. In this paper, we describe the model and a series of measurements of the total radiated power and the structural response due to a point force applied at the location of the ship's main propulsion engine. We show that to first order the radiation from a point force is due to engine room hull vibration only, and that the total radiation impedance is relatively independent of frequency.

ISSN:0001-4966    

DOI:10.1121/1.2003980

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Acoustic radiation from merchant vessels at blade rate frequency and harmonics is caused by direct radiation from cavitation volume fluctuations and from forced vibration of the ship hull caused by unsteady propeller forces. Reciprocal measurements were made on a structural scale model of a 600‐ft tanker (1: 100 scale) to determine the relationship between forced ship hull vibration and radiated power. Unsteady propeller forces have been predicted theoretically in order to estimate the acoustic power radiated by ship hull vibrations. Analytical methods have been used to predict cavitation volume fluctuations and the acoustic power radiated by these fluctuations. For a typical single screw merchant vessel, it is shown that the acoustic power at blade rate and harmonics radiated directly from cavitation volume fluctuations will dominate over the radiation from the hull response to unsteady propeller forces.

ISSN:0001-4966    

DOI:10.1121/1.2003986

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Analysis of calculated pulse shapes for ultrasonic waves reflected from a plane transducer is made with respect to the effect of transducer thickness and transducer backing material. Conditions affecting convergence of the amplitude value of the infinite series of pulses internally reflected in the transducer are discussed in detail. The significance of the acoustic impedance of the sample under study as well as that of the transducer is shown to be an essential criteria in selection of transducer backing material.

ISSN:0001-4966    

DOI:10.1121/1.2003991

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

When a step voltage is applied to an electrostrictive transducer, the decay of the terminal current is not monotone. Although this phenomena caused by piezoelectric reaction has already been confirmed for the thickness mode, [C. Kasai, D. Okuyama and Y. Kikuchi, “Transient Response Analysis of Piezoelectric Transducers Using Reflection and Transmission Coefficients at Their Surfaces,” Electron. Commun. Jpn56‐A(3), 19 (1973)] it has not been confirmed for the longitudinal mode using transversal effect. This paper presents an analytical method for longitudinal mode that is similar to that used for the thickness mode, and also shows that the numerical calculations based on this method approximately agrees with the experimental results for the samples of electrostrictive columnar and rectangular plate. By these results, it became clear that the current waveform depends on the electromechanical coupling factor of the transducer material and the time constant of the driving circuit of the transducer.

ISSN:0001-4966    

DOI:10.1121/1.2003995

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

The two basic acoustic baffles available for use to relatively large depths (i.e., nominally about 2500 feet) in the ocean without pressure compensation are the compliant tube and spring plate types. Both have unique acoustic and stress/failure characteristics with some expected similarities. Within the frequency range in which these baffles are generally used the acoustic transmission is largest when the incident radiation is normal to the baffle plane. For this case we can easily generate aTnetwork circuit model for each type of baffle. Different layers that have periodically related spatial construction to one another can be interfaced by joining appropriate terminals to accommodate a circuit format for the composite multilayered baffle. This paper is a brief on the background physics and analysis of the two baffles, their circuits, and a comparison of their various physical/spectral features.

ISSN:0001-4966    

DOI:10.1121/1.2004001

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Two sets of acoustical adjustments are being successfully applied to improving the tone and playing qualities of child‐size violins—3/4, 1/2, 1/4, 1/8, 1/10, and 1/16: (1) Tuning a pair of free plates of a given instrument using the Chladni pattern method to indicate where and how much wood to remove from each plate for desired frequency and damping characteristics of mode 2 and mode 5; (2) Applying the principle of second harmonic reinforcement to the low G string range of each instument by adjusting the Helmholtz air resonance to be more than an octave above the open G196 Hz—between 400 and 450 Hz—so that strong tones occur over a range of two or three notes an octave below the Helmholtz resonance as the broadband input from the bowed string activates the instrument. Methods of plate tuning and frequency adjustment of the Helmholtz air resonance will be discussed and illustrated and small violins will be played to demonstrate results.

ISSN:0001-4966    

DOI:10.1121/1.2004007

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Experiments have sought to determine the spectral changes that can be reliably measured when various bowing techniques are used, by the same performer or by different performers. The trained musician can generally identify the technique (legato, staccato, “col legno,” upbow or downbow, ponticello, etc.) through the distinctive timbres. This study has been limited to the violin, and the complexities of the electronic analysis, as well as the partially meaningful results will be presented. The difficulties include the room reverberation characteristics, the directional radiation of sound from the instrument, and the variance of the individual repeat of a given note, even without the inter‐performer variance. We carefullyavoidinclusion of psycho‐acoustic consideration.

ISSN:0001-4966    

DOI:10.1121/1.2004012

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP