Measurement of Sound Pressure Amplitude by Optical Methods

In this paper, frequency spectrum of infrasound signal collected was analyzed based on MATLAB. The infrasound power level of change with frequency distribution and the infrasound harmonic of each frequency component of the sound pressure amplitude can be made up judgment visually by frequency spectrum analysis and amplitude spectrum analysis, and thus we can obtain different conditions of infrasound properties scientifically and quantitatively.

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Prediction and Reduction of Aerodynamic Noise of the Multiblade Centrifugal Fan

Advances in Mechanical Engineering ◽

10.1155/2014/712421 ◽

2014 ◽

Vol 6 ◽

pp. 712421 ◽

Cited By ~ 1

Author(s):

Shuiqing Zhou ◽

Jun Wang

Keyword(s):

Flow Field ◽

Sound Pressure ◽

Acoustic Analysis ◽

Low Noise ◽

Aerodynamic Noise ◽

Hybrid Technique ◽

Field Calculation ◽

Pressure Amplitude ◽

Centrifugal Fan ◽

Hybrid Techniques

An aerodynamic and aeroacoustic investigation of the multiblade centrifugal fan is proposed in this paper, and a hybrid technique of combining flow field calculation and acoustic analysis is applied to solve the aeroacoustic problem of multiblade centrifugal fan. The unsteady flow field of the multiblade centrifugal fan is predicted by solving the incompressible Reynolds-averaged Navier-Stokes (RANS) equations with conventional computing techniques for fluid dynamics. The principal noise source induced is extracted from the calculation of the flow field by using acoustic principles, and the modeled sources on inner and outer surfaces of the volute are calculated with multiregional boundary element method (BEM). Through qualitative analysis, the sound pressure amplitude distribution of the multiblade centrifugal fan in near field is given and the sound pressure level (SPL) spectrum diagram of monitoring points in far field is obtained. Based on the analysis results, the volute tongue structure is adjusted and then a low-noise design for the centrifugal fan is proposed. The comparison of noise tests shows the noise reduction of improved fan model is more obvious, which is in good agreement with the prediction using the hybrid techniques.

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Optical Methods for the Measurement of the Sound Pressure in Liquids

The Journal of the Acoustical Society of America ◽

10.1121/1.1907607 ◽

1959 ◽

Vol 31 (1) ◽

pp. 24-28 ◽

Cited By ~ 21

Author(s):

M. A. Breazeale ◽

E. A. Hiedemann

Keyword(s):

Sound Pressure ◽

Optical Methods

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Simulation of Infrasound Pistonphone

Proceedings of the Institute for System Programming of RAS ◽

10.15514/ispras-2020-32(5)-14 ◽

2020 ◽

Vol 32 (5) ◽

pp. 181-198

Author(s):

Dmitrii Vital`Evich Golovin

Keyword(s):

Fundamental Frequency ◽

Sound Pressure ◽

Control Point ◽

Tuning Parameter ◽

Polytropic Index ◽

Heat Conducting ◽

Closed Volume ◽

Pressure Amplitude ◽

The Stability ◽

Semi Empirical

There are presented the results of numerical simulation of an applied acoustic problem – modeling of gas processes occurring in the measuring chamber of the infrasound pistonphone 3202 at different frequencies of piston oscillation (0.1 – 1000 Hz) and characterized by extremely small Mach numbers (9.1·10-7÷9.1·10-3). The simulation was performed using quasi-gas-dynamic (QGD) and quasi-hydrodynamic (QHD) equations of a viscous compressible heat-conducting gas with the use of a time-explicit difference scheme, all spatial derivatives was approximated by central differences. It is shown that QGD and QHD models can be used for a simulation of applied acoustics and, in particular, to the simulation of infrasonic pistonphone: the stability limits of the QGD and QHD algorithms in this problem were determined, the dependence of sound pressure on the tuning parameter α is investigated and it is shown that this dependence is quite small. The spectra of sound pressure at the control point calculated by QGD and QHD are given, their dependence on the tuning parameter α is shown, both models equally predict the value of the sound pressure amplitude at the fundamental frequency oscillations. At the end of the article, the sound pressure at the control point at the fundamental frequency oscillations obtained by using QGD and QHD is compared with the values calculated by using semi-empirical formula of sound pressure at closed volume for a case of small oscillations using the polytropic index obtained by Henry Gerber instead of the adiabatic coefficient.

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