The parabolic equation method for outdoor sound propagation
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TECHNICAL NOTES AND RESEARCH BRIEFS Paul B. Ostergaard 10 Glenwood Way, West Caldwell, New Jersey 07006 Editor’s Note: Original contributions to the Technical Notes and Research Briefs section are always welcome. Manuscripts should be double-spaced, and ordinarily not longer than about 1500 words. There are no publication charges, and consequently, no free reprints; however, reprints may be purchased at the usual prices. Advanced-degree dissertations in acoustics Editor’s note: Abstracts of Doctoral and Master’s theses will be wel- comed at all times. Please note that they must be double spaced, limited to 200 words, must include the appropriate PACS classification numbers, and be formatted as shown below ~don’t make the editor retype them, please!!. The address for obtaining a copy of the thesis is helpful. Please submit two copies. The parabolic equation method for outdoor sound propagation [43.28.Fp, 43.20.Bi]—Marta Galindo Arranz, Dept. of Acoustic Technology, Technical University of Denmark, DK-2800 Lyngby, Denmark 1996 (Ph.D.). The parabolic equation method ~abbreviated PE! transforms the elliptic Helmholtz equation into a parabolic wave equation, which solves an initial value problem. Solving an initial value problem is desirable in the study of propagation of waves through complex environments, where the closed solutions of boundary value problems turn out to be too complex. Three different applications of the Crank–Nicolson parabolic equation method, CNPE, are presented. The first two applications study variations of the ground in a homogeneous atmosphere. Propagation of the sound above a mixed impedance ground and up-slope sound propagation are investigated. In the third application, the influence of the atmosphere is studied, charac- terized, and implemented in the CNPE method. The refraction of the sound due to the wind and temperature gradients, and the scattering due to the turbulence of the atmosphere is taken into account in the calculations. The flexibility and powerfulness of the PE method are demonstrated in the re- port. In several aspects of PE the report presents important new ideas. Thesis advisor: Karsten B. Rasmussen. Development of methods for evaluation of pitch strength in musical tones [43.75.Mn, 43.66.Hg]—Alexander Galembo, St. Petersburg Institute of Cinema and Television, Ul. Pravdy 13, St. Petersburg 191126, Russia, February 1995 (Ph.D.). The work is based on acoustic analyses and perceptual evaluations of real and synthesized piano tones. In the first part, psychological factors which limit the reliability of judgments of tone quality, such as terminology, cross-modal masking ~hearing–tactile feedback!, and prejudices were analyzed, and recommendations given for how to limit the effects of such factors. In the second part, dealing with the perceptual evaluation and acoustical analysis of treble tones in the piano, it was experimentally demonstrated that a prominent noise component is present, mainly due to structure-borne sound following the blow of the hammer. For quantifying the influence on the perceived pitch strength, a measurement of the harmonic-to-noise ratio, using a method with adjustable comb filtering of short time segments of the signal was proposed. In a third part, the characteristic stretching of the partial frequencies in piano tones due to string stiffness was analyzed. It was shown that cepstral analysis, as well as the concept of harmonic product spectrum, can be used to visualize and measure inharmonicity. A new algorithm, ‘‘the inharmonic product spectrum,’’ was designed for more accurate measurements of the inharmonicity coefficient, using a method of parameter variation. In a generalized approach a tunable ‘‘inharmonic comb filter’’ was developed, giving fast and accurate measurements of inharmonicity as well as a new convenient way of visualizing tones from musical instru- ments. Thesis advisor: Prof. Y. Vakhitov. 2397 2397 J. Acoust. Soc. Am. 101 (4), April 1997 0001-4966/97/101(4)/2397/1/$10.00 © 1997 Acoustical Society of America Redistribution subject to ASA license or copyright; see http://acousticalsociety.org/content/terms. Download to IP: 128.114.34.22 On: Mon, 01 Dec 2014 00:30:17
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Transcript of The parabolic equation method for outdoor sound propagation
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TECHNICAL NOTES AND RESEARCH BRIEFS
Paul B. Ostergaard10 Glenwood Way, West Caldwell, New Jersey 07006
Editor’s Note: Original contributions to the Technical Notes and Research Briefs section are alwayswelcome. Manuscripts should be double-spaced, and ordinarily not longer than about 1500 words. Thereare no publication charges, and consequently, no free reprints; however, reprints may be purchased atthe usual prices.
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Advanced-degree dissertations in acousticsEditor’s note:Abstracts of Doctoral and Master’s theses will be we
comed at all times. Please note that they must be double spaced, limit200 words, must include the appropriate PACS classification numbersbe formatted as shown below~don’t make the editor retype them, please!.The address for obtaining a copy of the thesis is helpful. Please submicopies.
The parabolic equation method for outdoor sound propagation[43.28.Fp, 43.20.Bi]—Marta Galindo Arranz, Dept. of AcousticTechnology, Technical University of Denmark, DK-2800 Lyngby, Denm1996 (Ph.D.).The parabolic equation method~abbreviated PE! transformsthe elliptic Helmholtz equation into a parabolic wave equation, which solan initial value problem. Solving an initial value problem is desirable instudy of propagation of waves through complex environments, whereclosed solutions of boundary value problems turn out to be too compThree different applications of the Crank–Nicolson parabolic equamethod, CNPE, are presented. The first two applications study variationthe ground in a homogeneous atmosphere. Propagation of the sound abmixed impedance ground and up-slope sound propagation are investigIn the third application, the influence of the atmosphere is studied, chaterized, and implemented in the CNPE method. The refraction of the sodue to the wind and temperature gradients, and the scattering due tturbulence of the atmosphere is taken into account in the calculations.flexibility and powerfulness of the PE method are demonstrated in theport. In several aspects of PE the report presents important new ideas
Thesis advisor: Karsten B. Rasmussen.
2397 J. Acoust. Soc. Am. 101 (4), April 1997 0001-4966/97/101(
ibution subject to ASA license or copyright; see http://acousticalsociety.org/
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Development of methods for evaluation of pitch strength inmusical tones [43.75.Mn, 43.66.Hg]—Alexander Galembo, St.Petersburg Institute of Cinema and Television, Ul. Pravdy 13,Petersburg 191126, Russia, February 1995 (Ph.D.).The work is based onacoustic analyses and perceptual evaluations of real and synthesizedtones. In the first part, psychological factors which limit the reliabiliof judgments of tone quality, such as terminology, cross-momasking ~hearing–tactile feedback!, and prejudices were analyzedand recommendations given for how to limit the effects of sufactors. In the second part, dealing with the perceptual evaluationacoustical analysis of treble tones in the piano, it was experimentdemonstrated that a prominent noise component is present, mainly dstructure-borne sound following the blow of the hammer. For quantifythe influence on the perceived pitch strength, a measurement ofharmonic-to-noise ratio, using a method with adjustable comb filteringshort time segments of the signal was proposed. In a third part,characteristic stretching of the partial frequencies in piano tones dustring stiffness was analyzed. It was shown that cepstral analysiswell as the concept of harmonic product spectrum, can be used to visuand measure inharmonicity. A new algorithm, ‘‘the inharmonproduct spectrum,’’ was designed for more accurate measuremof the inharmonicity coefficient, using a method of parameter variatiIn a generalized approach a tunable ‘‘inharmonic comb filter’’ wdeveloped, giving fast and accurate measurements of inharmonicitwell as a new convenient way of visualizing tones from musical instments.
Thesis advisor: Prof. Y. Vakhitov.
23974)/2397/1/$10.00 © 1997 Acoustical Society of America
content/terms. Download to IP: 128.114.34.22 On: Mon, 01 Dec 2014 00:30:17
