Numerical calculation of the correlation moments of the sound field scattered by a rough surface

2000 ◽  
Vol 46 (3) ◽  
pp. 261-268
Author(s):  
V. F. Baranov ◽  
É. P. Gulin
Keyword(s):  
Numerical Calculation ◽  
Rough Surface ◽  
Sound Field

scholarly journals A Spectral Method for Two-Dimensional Ocean Acoustic Propagation

2021 ◽  
Vol 9 (8) ◽  
pp. 892
Author(s):  
Xian Ma ◽  
Yongxian Wang ◽  
Xiaoqian Zhu ◽  
Wei Liu ◽  
Qiang Lan ◽  
...  
Keyword(s):  
Numerical Calculation ◽  
Spectral Method ◽  
Collocation Method ◽  
Approximation Error ◽  
Sound Field ◽  
Acoustic Propagation ◽  
Two Dimensional ◽  
Chebyshev Collocation Method ◽  
Chebyshev Collocation ◽  
Wide Range

The accurate calculation of the sound field is one of the most concerning issues in hydroacoustics. The one-dimensional spectral method has been used to correctly solve simplified underwater acoustic propagation models, but it is difficult to solve actual ocean acoustic fields using this model due to its application conditions and approximation error. Therefore, it is necessary to develop a direct solution method for the two-dimensional Helmholtz equation of ocean acoustic propagation without using simplified models. Here, two commonly used spectral methods, Chebyshev–Galerkin and Chebyshev–collocation, are used to correctly solve the two-dimensional Helmholtz model equation. Since Chebyshev–collocation does not require harsh boundary conditions for the equation, it is then used to solve ocean acoustic propagation. The numerical calculation results are compared with analytical solutions to verify the correctness of the method. Compared with the mature Kraken program, the Chebyshev–collocation method exhibits higher numerical calculation accuracy. Therefore, the Chebyshev–collocation method can be used to directly solve the representative two-dimensional ocean acoustic propagation equation. Because there are no model constraints, the Chebyshev–collocation method has a wide range of applications and provides results with high accuracy, which is of great significance in the calculation of realistic ocean sound fields.

Improving Design of Muffler Based on Three-Dimension Numerical Calculation of Fluid and Sound Field

2011 ◽  
Vol 295-297 ◽  
pp. 2300-2303
Author(s):  
Hai Jun Zhao ◽  
Jia Dong Chang ◽  
Hong Jie Zhao
Keyword(s):  
Numerical Calculation ◽  
Environmental Pollution ◽  
Rotational Speed ◽  
Pressure Loss ◽  
Sound Field ◽  
Original Structure ◽  
Three Dimension ◽  
Vehicle Noise ◽  
Important Method ◽  
Aerodynamic Quality

Presence problem of exhaust muffler is anal sized, using three three-dimension numerical calculation of fluid and sound field improvement on original structure is performed, and improving results are certificated. It is shown that insert loss under every rotational speed all reach to the standard of 28dB（A）, and the noises of stationary end tube on the attention frequency band are all smaller than 5 dB（A） , and its pressure loss is decreased by about 32% than 7.6kPa of original structure muffler. So performance of the muffler is evidence increased, an important method is provided for decreasing whole vehicle noise, improving aerodynamic quality and reducing environmental pollution.

Research on Numerical Calculation Method to Aerodynamic Noise in High Velocity Environment

2013 ◽  
Vol 655-657 ◽  
pp. 809-812 ◽  
Author(s):  
Li Jun Zhang ◽  
Xiao Jiao Chen ◽  
Min Li ◽  
Yue Fan ◽  
Qiang Fu
Keyword(s):  
Numerical Calculation ◽  
Boundary Element ◽  
Field Distribution ◽  
Sound Field ◽  
High Strength ◽  
Aerodynamic Noise ◽  
Acoustic Analogy ◽  
Analogy Method ◽  
Calculation Results ◽  
Numerical Calculation Method

At present, the flight velocity and flight performance of an aircraft are higher, so that aerodynamic noise caused by an engine jet in the take-off and flight processes can reach 160 dB. The high strength of the jet aerodynamic noise is very harmful to vehicle drivers, vehicle structures and airborne equipments. Two numerical calculation methods to aerodynamic noise, the FW-H acoustic analogy method and the FW-H acoustic analogy and boundary element combining method, were introduced. These two methods were used to predict the aerodynamic noise, and the numerical calculation results were compared with the physical experimental results. Results show that the FW-H acoustic analogy method can predict aerodynamic noise. However, it cannot predict the sound field distribution. The FW-H acoustic analogy and boundary element combining method is able to predict the sound field distribution with sound reflection.

Decay of Temporary Threshold Shift in Noise

1973 ◽  
Vol 16 (2) ◽  
pp. 267-270 ◽  
Author(s):  
John H. Mills ◽  
Seija A. Talo ◽  
Gloria S. Gordon
Keyword(s):  
Sound Field ◽  
Threshold Shift ◽  
Temporary Threshold Shift ◽  
Octave Band ◽  
Band Noise ◽  
Lower Asymptote

Groups of monaural chinchillas trained in behavioral audiometry were exposed in a diffuse sound field to an octave-band noise centered at 4.0 k Hz. The growth of temporary threshold shift (TTS) at 5.7 k Hz from zero to an asymptote (TTS ∞ ) required about 24 hours, and the growth of TTS at 5.7 k Hz from an asymptote to a higher asymptote, about 12–24 hours. TTS ∞ can be described by the equation TTS ∞ = 1.6(SPL-A) where A = 47. These results are consistent with those previously reported in this journal by Carder and Miller and Mills and Talo. Whereas the decay of TTS ∞ to zero required about three days, the decay of TTS ∞ to a lower TTS ∞ required about three to seven days. The decay of TTS ∞ in noise, therefore, appears to require slightly more time than the decay of TTS ∞ in the quiet. However, for a given level of noise, the magnitude of TTS ∞ is the same regardless of whether the TTS asymptote is approached from zero, from a lower asymptote, or from a higher asymptote.

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