摘要:

With the advent of commercial jet airline operations, increased importance must be placed upon acoustical considerations in airport design. This paper reviews the relationships between the noise resulting from commercial jet and propeller airliner operations, including takeoff, taxi, and idle, for various projected traffic densities and various airport building functional design criteria. Presently used criteria are explained and new criteria are suggested to fill a gap in the over‐all evaluation procedure for short time noises. Methods and examples are presented which expedite initial visualization of the major acoustical factors in an airport design situation, facilitate decisions for preliminary airport building layout, and enable evaluation of possible wall and roof structures.

ISSN:0001-4966    

DOI:10.1121/1.1907751

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

A set of phenomenological equations, valid at all frequencies, is proposed for the rates of change of internal relaxation parameters describing molecular excitations and structural changes in liquid. An Onsager coupling is found to exist between the rate equations for the parameters and the pressure tensor, so that the diagonal terms of the pressure contain a linear sum of thermodynamic affinities governing the internal irreversible processes. These affinities can be eliminated from the pressure, using the rate equations, to give a complex compressional modulus, reducing to a bulk viscosity term at low frequencies and a contribution to the bulk modulus at very high frequencies. The bulk viscosity is calculated at 20°C for two nonassociated liquids, on the assumption of a single thermal and single structural relaxation time, with use of a “hole” model of structural relaxation based on a shear viscosity theory of Mooney. The acoustic absorption coefficient is computed from the bulk viscosity, yielding fair order‐of‐magnitude agreement with experiment in both cases.

ISSN:0001-4966    

DOI:10.1121/1.1907752

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

The propagation of free harmonic waves along a hollow circular cylinder of infinite extent is discussed within the framework of the linear theory of elasticity. A characteristic equation appropriate to the circular hollow cylinder is obtained by use of the Helmholtz potentials for arbitrary values of the physical parameters involved. Axially symmetric waves, the limiting modes of infinite wavelength, and a special family of equivoluminal modes are derived and discussed as degenerate cases of the general equations.

ISSN:0001-4966    

DOI:10.1121/1.1907753

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

The results are given of a numerical evaluation of a characteristic equation derived in Part I, appropriate to free harmonic waves propagated along a hollow cylinder of infinite extent. This equation is evaluated for some representative cylinders covering the entire range from thin shells to solid cylinders, and the results are compared with the corresponding results of a shell theory. Observations are made regarding the variation of the frequency spectrum with the physical parameters, as well as the range of applicability of shell theories.

ISSN:0001-4966    

DOI:10.1121/1.1907754

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

The Rayleigh inextensional theory for thin shells is employed to predict the natural frequencies of a sphere‐cone combination. For a particular case, the calculated and measured natural frequencies of shells of nonuniform thickness are determined. In comparing the experimental values of the lowest five “bell” frequencies with the predicted theoretical inextensional theory, there is very good agreement. This indicates that the method may be used for many missile configuration and jet engine applications.

ISSN:0001-4966    

DOI:10.1121/1.1907755

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

For the purpose of measuring the properties of cushioning materials under simulated space conditions, it has been necessary to calibrate accelerometers for use in this unusual environment. In this paper, calibrations over the temperature range from −320°F to +80°F, and at an atmospheric pressure of 5×10−5mm Hg, are reported for several different types of barium titanate accelerometers. These calibrations were obtained at several frequencies between 20 cps and 100 cps by the optical viewing method.

ISSN:0001-4966    

DOI:10.1121/1.1907756

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

A brief discussion given, in terms of ray theory, of the character of explosive sound which has propagated for long distances in the ocean. In addition to the arrivals previously studied, a “leakage” arrival has been observed. This arrival has been analyzed for travel time and spectrum level. The attenuation rate has been plotted as a function of frequency. The similarity of this attenuation rate to the theoretical and experimental attenuation rates for the surface channel indicates that the leakage arrival is due to energy that in part travels in the surface channel and in part is refracted.

ISSN:0001-4966    

DOI:10.1121/1.1907757

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

The random incidence sound absorption coefficient is calculated for a narrow strip of absorbing material set in an otherwise reflecting plane. The assumptions made are that the material is of the locally reacting type, with a real normal admittance. The effect of an imaginary component of admittance is discussed qualitatively.The results show the increase in absorption coefficient that occurs at small widths due to diffraction. Consideration is also given to the absorption of rectangular patches having both dimensions in the diffraction range. The standard reverberation room measurement of sound absorption is examined.

ISSN:0001-4966    

DOI:10.1121/1.1907758

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

Approximately 20 db of TTS at 3 and 4 kc, measured 2 min after cessation of the TTS‐producing stimulation, was produced in 14 normal listeners by three different exposures to 1200‐ to 2400‐cps noise: to 106 db SPL for 12 min, to 98 db for 27 min, and to 90 db for 117 min. Despite the fact that the TTS produced at other frequencies was different for the three exposures, the courses of recovery at 3 and 4 kc were indistinguishable. From these results and those of others, it is concluded that the course of recovery from TTS is uniquely determined by the value of TTS at 2 min recovery: i.e., by the TTS remaining after the first fast recovery process, the so‐calledR‐1 recovery process, has run its course.

ISSN:0001-4966    

DOI:10.1121/1.1907759

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

A computational procedure is presented for determining the loudness of multicomponent tones. The procedure uses the lambda loudness function and has just two basic assumptions: (1) loudness of components add as the sum of their squares, and (2) the effect of masking is to subtract a constant amount of loudness. With these two assumptions, the loudness data of Fletcher and Munson for multicomponent tones are predicted, using the lambda function and the masking data of Wegel and Lane for the necessary predictive terms. This procedure gives better accuracy than the original calculational schema of Fletcher and Munson, even though no constants are determined from the data. In fact the three sets of data (loudness scaling, masking, and multicomponent loudness) can be used such that any two will correctly predict the third. It seems possible that the lambda function may provide better integration of auditory data than other loudness functions.

ISSN:0001-4966    

DOI:10.1121/1.1907760

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP