Reconstruction of Sound Sources of Gear Transmission Mechanism by Planar Near Field Acoustical Holography

2012 ◽  
pp. 247-255 ◽  
Author(s):  
Abbassia Derouiche ◽  
Nacer Hamzaoui ◽  
Taoufik Boukharouba
Keyword(s):  
Near Field ◽  
Gear Transmission ◽  
Transmission Mechanism ◽  
Sound Sources ◽  
Acoustical Holography

Near-Field Beamforming Source Localization for Gear Transmission in a Semi-Anechoic Room

2014 ◽  
Vol 1016 ◽  
pp. 261-266
Author(s):  
Abbassia Derouiche ◽  
Nacer Hamzaoui
Keyword(s):  
High Resolution ◽  
Field Distribution ◽  
Source Localization ◽  
Phased Array ◽  
Near Field ◽  
Spur Gear ◽  
Gear Transmission ◽  
Beam Forming ◽  
Sound Sources ◽  
Acoustic Surveillance

In this study, we discussed the sound sources localization and characterization for a spur gear transmission, which deals with a vibro-acoustic surveillance for predictive maintenance. The technique uses is based on the near-field Beam forming using Bartlett and Capon estimators. The measurements done on the gear transmission with a rectangular phased array of microphones were performed in acoustics and vibration laboratory (LVA) of the INSA of Lyon, in a semi-anechoic room. The gear transmission was considered sometimes open and sometimes closed. The results are presented as an image showing the acoustic field distribution radiated by the gear transmission at the most energetic frequencies. Both estimators have satisfactory results, but even better for the method with high resolution capon.

Sound field separation of multiple coherent sound sources with single measurement surface

2021 ◽  
pp. 107754632110201
Author(s):  
Jin Mao ◽  
Jinfu Du ◽  
Kai Liu ◽  
Jiang Liu ◽  
Yahui Cui
Keyword(s):  
Near Field ◽  
Sound Field ◽  
Single Measurement ◽  
Sound Sources ◽  
Equivalent Source ◽  
Coherent Sources ◽  
Measurement Surface ◽  
Acoustical Holography ◽  
Field Separation ◽  
Source Number

Sound field separation based on near-field acoustical holography has been developed worldwide, but with the increase in the number of sound sources, traditional measurement methods and calculation methods will generate more workload. To reduce the number of measuring points and save calculation time, the sound field separation of multiple coherent sources with a single measurement surface is proposed. On the basis of separating two coherent sources with this method, the separation formula of more sources based on an equivalent source method is given. Through numerical simulation, the effects of the number of holographic surface measuring points, measuring distance, array shape, and equivalent source number on the calculation accuracy of the sound field separation were compared at different frequencies. The correctness and effectiveness of the sound field separation method with a single surface are verified by actual experiments.

USE OF RIGID REFLECTORS FOR THE VIRTUAL INCREASE OF FIELD DATA IN THE NEAR-FIELD ACOUSTICAL HOLOGRAPHY

2007 ◽  
Vol 15 (01) ◽  
pp. 49-61 ◽  
Author(s):  
SUNG-IL KIM ◽  
JEONG-GUON IH ◽  
JI-HOON JEONG
Keyword(s):  
Boundary Element Method ◽  
Transfer Matrix ◽  
Field Data ◽  
Near Field ◽  
Measurement Data ◽  
Source Reconstruction ◽  
Matrix Equations ◽  
Inverse Boundary ◽  
Additional Information ◽  
Acoustical Holography

This paper suggests the use of rigid reflectors to provide additional information for source reconstruction in near-field acoustical holography based on the inverse boundary element method. The additional field pressure and transfer matrix equations introduced provide a virtual increase in the measurement data without increasing the number of sensors or altering their arrangement, which could cost more than using reflectors. In order to validate this method, we successfully reconstruct a vibrating ellipse.

Ground Attenuation Factor Based on Measurements

2021 ◽  
Vol 263 (3) ◽  
pp. 3436-3447
Author(s):  
Dan Lin ◽  
Andrew Eng
Keyword(s):  
Near Field ◽  
Attenuation Factor ◽  
Measurement Data ◽  
Low Frequency ◽  
Sound Sources ◽  
Frequency Sound ◽  
Sound Levels ◽  
Different Types ◽  
Noise Measurements ◽  
Field Sound

Assumptions made on the ground types between sound sources and receivers can significantly impact the accuracy of environmental outdoor noise prediction. A guideline is provided in ISO 9613-2 and the value of ground factor ranges from 0 to 1, depending on the coverage of porous ground. For example, a ground absorption factor of 1 is suggested for grass ground covers. However, it is unclear if the suggested values are validated. The purpose of this study is to determine the sound absorption of different types of ground by measurements. Field noise measurements were made using an omnidirectional loudspeaker and two microphones on three different types of ground in a quiet neighborhood. One microphone was located 3ft from the loudspeaker to record near field sound levels in 1/3 and 1 octave bands every second. The other microphone was located a few hundred feet away to record far field sound in the same fashion as the near field microphone. The types of ground tested were concrete, grass, and grass with trees. Based on the measurement data, it was found that grass and trees absorb high frequency sound well and a ground factor of 1 may be used for 500Hz and up when using ISO 9613-2 methodology. However, at lower frequencies (125 Hz octave band and below), grassy ground reflects sound the same as concrete surfaces. Trees absorb more low frequency sound than grass, but less than ISO 9613-2 suggested.

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