摘要:

A procedure is described for obtaining the stress constante33for an arbitrary piezoelectric transducer operating in the thickness mode. A closed‐form solution is is developed which uses measurements of the electrical impedance of the transducer as input. Verification of the calculated parameters is accomplished by incorporating them into a computer model of the transducer. A discussion of various methods of obtaining the clamped capacitanceC0is included as well as a calculation of an equivalent resistance to represent losses in the ceramic. Numerical examples are presented.

ISSN:0001-4966    

DOI:10.1121/1.382109

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

The theory of a broadband constant directivity transducer is developed. The transducer is an array of isophase, omnidirectional elements on an acoustically transparent spherical surface. It is shown that, with appropriate amplitude shading of the array elements, the beam pattern has no side lobes and the directivity is constant at all frequencies above a cutoff frequency (determined by the beam width and the radius of the sphere.) A shading function is derived, which consists of a simple linear combination of powers of cos ϑ, and several beam patterns are calculated.

ISSN:0001-4966    

DOI:10.1121/1.382110

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

An improved design is made for a spherical multimode hydrophone by dividing each hemisphere into two zones and selecting the position of the line of division between them, so that the resonances associated with higher modes of the spherical shell vibrations, specificallyn=3 andn=5 modes in the present case, are eliminated. The elimination of these resonances has led to the provision of a frequency‐independent dipole pattern over a wide range of frequencies. The present theory includes the effect of spherical shell bending, since it is important at higher modes. Accordingly, the resonant frequencies are clearly identified by the associated mode numbers. In both theory and experiment, these resonant effects were eliminated by employing the newly designed hydrophone.

ISSN:0001-4966    

DOI:10.1121/1.382111

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Modifications to prior theory yield expressions for the frequency response and equivalent lumped elements of a condenser microphone in terms of its fundamental geometrical and material properties. Results of the analysis show excellent agreement with experimental data taken on B&K pressure microphone types 4134 and 4146.

ISSN:0001-4966    

DOI:10.1121/1.382112

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Previous treatments of fiber‐optic hydrophone sensitivity have neglected the effect of dimensional changes of the fiber in response to acoustic pressure. It is shown here that the changes in length actually contribute more to hydrophone sensitivity than do the refractive index changes; the two contributions are of opposite sign. An experiment verifying the sensitivity calculation was performed using 60‐kHz pulses from a spherical source.

ISSN:0001-4966    

DOI:10.1121/1.382113

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Studies undertaken in the Straits of Florida and the Tongue of the Ocean (TOTO), Bahamas, have established that silky sharks,Carcharhinusfalciformis, while approaching a source of underwater sound, will withdraw rapidly from its vicinity if specified changes occur in the nature of the transmitted sound. These changes include: 1) an increase in level of the sound being transmitted (approximately 20 dB) and 2) an abruptness by which that level is achieved. Augmenting factors may include sudden changes in the spectral or temporal qualities of the transmitted sound. Although a biological sound (killer whale scream) could elicit clear withdrawal, it possessed no unique quality; rather, more simply constructed sounds, possessing only a restricted band of frequencies and lacking frequency‐modulation, were equally effective. Habituation of the response was apparent during successive tests. All results closely followed those obtained on lemon sharks,Negaprionbrevirostris, during a concurrent study (to be reported elsewhere). In the presence of added stimulants (chopped, fresh fish) withdrawal could be elicited in small silky sharks for only a short time. Limited testing of oceanic whitetip sharks,Carcharhinuslongimanus, showed that extremely limited withdrawal could also be elicited in that species.

ISSN:0001-4966    

DOI:10.1121/1.382114

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

The real part of the complex Young’s modulus of whole frog sartorius muscle in the resting state was derived from step pulse propagation data in the frequency range of 1.0–10 000 Hz. The derivation was based on Fourier integral analysis of the shapes of the propagated pulses to obtain velocities and attenuation coefficients for various harmonic frequencies. The results were consistent with previous sinusoidal wave propagation studies in the higher‐frequency range. The general frequency response of the muscle was analogous to the ’’standard linear solid’’ model. The relaxation time spectrum derived from the modulus–frequency function showed similar spectral contents to spectra obtained with other methods. The advantages and limitations of the pulse method are discussed.

ISSN:0001-4966    

DOI:10.1121/1.382115

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Causes for the decrease in rate of piano tone decay with time of tone duration were investigated, including the following: different rates for different vibration modes or groups of modes, nonlinear transformation of mechanical energy to acoustical energy, storage of mechanical energy for subsequent acoustical radiation, transfer of energy between string modes perpendicular and parallel to the bridge, interference among strings that are almost exactly in tune, and change in rate of energy transfer from the multiple‐string source to the bridge during the transition from an initial in‐phase condition to a later out‐of‐phase condition. The last two closely related factors were found to control the rate change in most cases.

ISSN:0001-4966    

DOI:10.1121/1.382116

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Speech analysis and synthesis by linear prediction is based on the assumption that the short‐time spectral envelope of speech can be represented by a number of poles. An all‐pole representation does not provide an accurate description of speech spectra, particularly for nasals and nasalized sounds. This paper presents a method for characterizing speech in terms of the parameters of a pole‐zero model. In this method,an impulse response representing the composite filtering action of the glottal wave, the vocal tract, the radiation, and the speech recording system is first constructed from the speech signal.This impulse response is obtained by performing several stages of all‐pole LPC analysis. The pole‐zero parameters are determined from the impulse response by solving a set of simultaneous linear equations. The method, being noniterative, is very suitable for automatic analysis of speech. The method has been applied to real speech data and the results show that the speech spectra derived from the pole‐zero model agree very closely with the actual spectra derived by direct Fourier analysis.

ISSN:0001-4966    

DOI:10.1121/1.382117

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Two experimental techniques were used in this study: (1) an analysis of F0contours of French sentences containing words likely to express the speaker’s attitude (modals, negative, adverbs, quantifiers) and (2) listener’s judgements of the naturalness of synthetic sentences in which the F0contour was systematically manipulated. The F0contours were characterized by schematic patterns [J. Vaissière Res.Lab.Electron., Q.Prog.Report No. 115, MIT, 251–262 (1975)]. For all the sentences that were studied, the configurations of patterns frequently observed in the analyzed corpus were judged most natural when synthethized. This result suggest that the features of the F0contours most relevant to naturalness are preserved in the pattern representation. Three types of patterns were distinguished: (1) a prominent, demarcative pattern (P2); (2) a prominent, nondemarcative pattern (PE); (3) nonprominent, nondemarcative patterns. A P2 pattern often occurred at the end of a syntactic constituent. Listeners’ judgements showed that a P2 at the end of a syntactic constituent is rarely required for naturalness, but a P2 in contradiction to syntax causes unnaturalness. Prominent patterns (P2 or PE) often occurred on negatives, adverbs, and quantifiers. However, the presence or absence of a prominent pattern on these words does not affect naturalness.

ISSN:0001-4966    

DOI:10.1121/1.382118

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP