Sound Radiation Characteristics of Lightweight Roof Constructions Excited by Rain

1994 ◽  
Vol 1 (4) ◽  
pp. 249-270 ◽  
Author(s):  
Hiromi Suga ◽  
Hideki Tachibana
Keyword(s):  
Transmission Loss ◽  
Power Level ◽  
Sound Radiation ◽  
Sound Intensity ◽  
Sound Power ◽  
Radiation Characteristics ◽  
Natural Rainfall ◽  
Artificial Rainfall ◽  
Sound Power Level ◽  
Measurement Results

In order to investigate the sound radiation characteristics of lightweight roof constructions when excited by rainfall, an artificial rainfall apparatus was constructed to simulate natural rainfall conditions. From the measurement results, it can be seen that the facility developed is practically applicable for the examination of the sound radiation characteristics of rain noise. It was therefore used in the measurement of sound power of 20 lightweight roofs. In addition, the relationship between sound power level and sound transmission loss measured by the sound intensity method was investigated statistically. As a result, it has been shown that a linear relationship exists between them and there is a possibility of estimating the sound power level from the transmission loss.

scholarly journals A Comparison of Vibroacoustic Response of Isotropic Plate with Attached Discrete Patches and Point Masses Having Different Thickness Variation with Different Taper Ratios

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Bipin Kumar ◽  
Vinayak Ranjan ◽  
Mohammad Sikandar Azam ◽  
Piyush Pratap Singh ◽  
Pawan Mishra ◽  
...  
Keyword(s):  
Power Level ◽  
Low Frequency ◽  
Sound Radiation ◽  
Radiation Efficiency ◽  
Thickness Variation ◽  
Sound Power ◽  
Sound Power Level ◽  
Radiation Behavior ◽  
Thickness Variations ◽  
Different Thickness

A comparison of sound radiation behavior of plate in air medium with attached discrete patches/point masses having different thickness variations with different taper ratio of 0.3, 0.6, and 0.9 is analysed. Finite element method is used to find the vibration characteristics while Rayleigh integral is used to predict the sound radiation characteristics. Minimum peak sound power level obtained is at a taper ratio of 0.6 with parabolic increasing-decreasing thickness variation for plate with four discrete patches. At higher taper ratio, linearly increasing-decreasing thickness variation is another alternative for minimum peak sound power level suppression with discrete patches. It is found that, in low frequency range, average radiation efficiency remains almost the same, but near first peak, four patches or four point masses cause increase in average radiation efficiency; that is, redistribution of point masses/patches does have effect on average radiation efficiency at a given taper ratio.

Simulation and Analysis of the Radiated Acoustic Field Measurement of the Underwater Vehicle Based on NAH

2012 ◽  
Vol 503-504 ◽  
pp. 1575-1579
Author(s):  
Shao Chun Ding ◽  
Lin Na Zhou ◽  
Jing Jun Lou ◽  
Shi Jian Zhu
Keyword(s):  
Acoustic Field ◽  
Sound Pressure ◽  
Power Level ◽  
Sound Intensity ◽  
Sound Power ◽  
Pressure Method ◽  
Sound Power Level ◽  
Measuring Surface ◽  
Source Level ◽  
The Mean

we use the NAH method for the simulation and analysis of sound power level and source level with the plan measuring surface under the same distance and size. The sound intensity integral method, the mean square sound pressure method and the NAH reversal method have been adopted in this paper. We also compare the sound power level between the plan measuring surface and the cylinder measuring surface, thus helps verifying the accuracy of the measurement of the radiated acoustic field based on the method of NAH. The conclusion we have drawn here can also provides dependable experimental basis for the choosing of measuring surfaces

Sound Power Measurements in the Near Field of Transformers

2012 ◽  
Author(s):  
Michael Ertl ◽  
Hermann Landes
Keyword(s):  
Sound Pressure ◽  
Power Level ◽  
Near Field ◽  
Sound Field ◽  
Sound Intensity ◽  
Sound Level ◽  
Numerical Analyses ◽  
Sound Power ◽  
3D Fem ◽  
Sound Power Level

The international standard for the determination of the sound power level of transformers allows both the sound pressure and the sound intensity measurement method. Since the sound measurements take place in the reactive near-field next to the vibrating transformer tank walls, local disturbances influence the sound field characteristics at the measurement positions. As a result, the measured mean sound power level differs commonly up to 6dB at comparative measurements with both methods. Beyond these near field effects, the influence of an industrial measurement environment (background sound sources, hard-reflecting floor, semi-reverberant walls, and standing waves) to the sound pressure and sound intensity field characteristics is investigated. Hereby, numerical analyses based on 3D-FEM with consideration of the fluid-structure-coupling are used. The measured sound level differences can be re-produced and clarified in numerical analyses.

Sound Intensity Mapping on Single Cylinder Direct Injection Diesel Engine with The Application of Palm Oil Methyl Ester Biodiesel

2021 ◽  
Vol 18 (2) ◽  
pp. 8833-8844
Author(s):  
Mohd Shahrir Mohd Sani ◽  
J.M. Zikri ◽  
A. Abdul Adam
Keyword(s):  
Methyl Ester ◽  
Palm Oil ◽  
Engine Speed ◽  
Power Level ◽  
Sound Intensity ◽  
Sound Power ◽  
Noise Emission ◽  
Emission Analysis ◽  
Intensity Mapping ◽  
Sound Power Level

The utilisation of biodiesel nowadays has become familiar with rapid production types of biodiesel in order to replace the dependency on the fossil fuel parallel to the implementation of green technology that emphasises the products to be more environmental-friendly. Nevertheless, the emerges of various kinds of biodiesel cannot be simply used, despite using the biodiesel does not need any major modification on the engine; it still needs a few analyses that must be done to determine whether it will give advantages or disadvantages. Therefore, this research was carried out to investigate the effect of using palm oil methyl ester (POME) biodiesel on the engine in terms of noise emission. The sound intensity mapping method was used to indicate the effectiveness of the biodiesel by identifying the noise radiation. Along with the mapping, the sound power level (SPL) is also being obtained to provide a clear comparison between the parameters. Generally, switching up the engine speed and load increased the sound power level. Based on the results obtained related to the SPL, the intensity mapping tends to show a higher colour-coded in the noise source image for the higher engine speed and load setup. It was found that the engine speed and load give a significant contribution to noise emission produced by the engine, and it can be inferred that this method can be utilised to accomplish the noise emission analysis.

Sound Radiation Analysis of a Longwall Cutting Drum

2013 ◽  
Author(s):  
Junyi Yang ◽  
Hugo E. Camargo ◽  
David S. Yantek
Keyword(s):  
Finite Element ◽  
Power Level ◽  
Sound Radiation ◽  
Cylindrical Part ◽  
Acoustic Properties ◽  
Mine Safety ◽  
Sound Power ◽  
Sound Power Level ◽  
Safety And Health ◽  
Study Results

Operators of longwall mining systems experience sound levels of 93–105 dB(A) and receive noise exposures that place them at risk of noise-induced hearing loss. To address the problem, the National Institute for Occupational Safety and Health (NIOSH*) Office of Mine Safety and Health Research (OMSHR) has conducted research to develop engineering noise controls for longwall systems. In previous field surveys, the sound radiated by the cutting drums was identified as a major hazard, especially considering their close proximity to the operators. Cutting drums are complex structures consisting of curved metal pieces welded together, and NIOSH has used modeling and simulation to characterize the acoustic properties of this structure. Based on a finite element (FE) model of the drum, the boundary element method (BEM) was used to predict the sound radiated from the vibrating drum due to an excitation force applied to one of the cutting bits. Simulations were used to examine the following with respect to the radiated sound power: (1) the ramifications of adding the welds to the model rather than assuming direct attachment between the metal components; (2) the effect of weld stiffness; (3) the relative contributions of the vanes and the cylindrical part of the drum; and (4) the sensitivity to the direction of the applied force. Parametric studies have shown that including the weld in the finite element model has a significant effect on the predicted sound power level, while varying the weld Young’s modulus by 20% does not radically change the sound radiation. Panel contribution analysis indicates that the vanes contribute much more to the total sound power level, as compared to the cylindrical part of the drum. Consequently, it is expected that damping treatments would be most effective at controlling noise radiation if applied to the vanes rather than to the cylindrical portion. Finally, case study results show that the sound power levels are most sensitive to the tangential and bending forces above 500 Hz. For frequencies below 500 Hz, the sound power level is most sensitive to axial and bending forces.

Effect on Measurement of the Radiated Acoustic Field of Underwater Structure Based on NAH with Swinging Measuring Surface

2012 ◽  
Vol 197 ◽  
pp. 778-781
Author(s):  
Lin Na Zhou ◽  
Shao Chun Ding ◽  
Ruo Yu Zhang ◽  
Jing Jun Lou ◽  
Shi Jian Zhu
Keyword(s):  
Sound Pressure ◽  
Power Level ◽  
Near Field ◽  
Sound Intensity ◽  
Sound Power ◽  
Mean Square ◽  
Sound Power Level ◽  
Measuring Surface ◽  
Underwater Structure ◽  
Acoustical Holography

This paper analyzes the effects of the swinging NAH(Near field Acoustical Holography) measuring array on measurement of the sound power level of underwater structure. We use the method of sound intensity integral, the method of mean square sound pressure and the method of NAH reversal pressure to calculate the sound power level under certain collection of frequency with measuring surface in different states. We also analyze the relative error of results acquired by those methods, which can help validating the reliability and the error estimate of the results calculated with NAH.

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