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.

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 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.

A Study on Estimating Gasoline Engine Radiated Noise Based on Surface Vibration Measurement

2014 ◽  
Vol 694 ◽  
pp. 509-513 ◽  
Author(s):  
Guo Xu Cui ◽  
Can Song Gu ◽  
Hui Gao
Keyword(s):  
Gasoline Engine ◽  
Power Level ◽  
Test Method ◽  
Vibration Measurement ◽  
Vibration Velocity ◽  
Sound Power ◽  
Surface Vibration ◽  
Radiated Noise ◽  
Sound Power Level ◽  
Measuring Surface

A study on the method of estimating gasoline engine radiated noise by measuring surface vibration is carried out. Firstly, the theoretical basis and test method is studied. Then an experiment is carried out on a four-cylinder gasoline engine. By measuring the engine surface vibration velocity, the sound power level of these engine parts and of the engine body is calculated. The result shows that the estimation of engine radiated noise is accurate. It shows the sound power level of gasoline engine can be predicted by surface vibration.

Analysis of the Sound Power Level Emitted by Portable Electric Generators (Outdoor Powered Equipment) Depending on Location and Measuring Surface

2013 ◽  
Vol 430 ◽  
pp. 266-275 ◽  
Author(s):  
Elena Postelnicu ◽  
Valentin Vladut ◽  
Cristian Sorica ◽  
Petru Cardei ◽  
Ion Grigore
Keyword(s):  
Noise Source ◽  
Power Level ◽  
Acoustic Power ◽  
Sound Power ◽  
Noise Emission ◽  
Sound Power Level ◽  
Measuring Surface ◽  
Measurement Surface ◽  
Electric Generators

Acoustic power is a measure which must be specified on the outdoor used equipments and its determination depends on several factors: the place where the equipment works (indoor or outdoor), the placement of the microphones for its determination (the distance less or greater from the noise source), the shape of the measurement surface (parallelepiped or hemispherical). This paper aims to analyze the values obtained in these situations and interpret the data to determine the influence that each factor has on the acoustic power compared with the values obtained (permissible) according to Directive regarding noise emission D 2000/14/EC.

scholarly journals The Research of Acoustic Emission of a Low-Power Aircraft Engine

2018 ◽  
Vol 2018 (3) ◽  
pp. 14-25
Author(s):  
Michał Gęca ◽  
Konrad Pietrykowski ◽  
Karol Rosiński
Keyword(s):  
Sound Pressure ◽  
Power Level ◽  
Aircraft Engine ◽  
Sound Level ◽  
Sound Power ◽  
Research Model ◽  
Confined Space ◽  
Sound Power Level ◽  
Model Aircraft ◽  
Level Meter

Abstract This paper presents the methodology and investigation of the sound power level produced by a radial piston aircraft engine operating at varied speeds. The research model aircraft engine of a maximum power of 5.5 kW with a two-bladed airscrew was placed on a test bend. Its sound power level was calculated from the sound pressure level measured at 9 measurement points distributed on a hemispherical surface in a confined space in line with PN-EN 3744. Mean sound power generated by the ASP FS400AR engine is 96 dB at idle (2,880 rpm) and 105 dB at a cruising speed (4,740 rpm). Accordingly, it can be concluded that a sound level meter registered a higher sound power level at the points in front of the model aircraft engine than at the points behind it, whereas the lowest sound power level was registered directly above the engine.

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