Near-field acoustical holography-based noise source analysis of an installed, afterburning F404 engine

2021 ◽  
Vol 150 (4) ◽  
pp. A213-A213
Author(s):  
Logan T. Mathews ◽  
Kevin M. Leete ◽  
Kent L. Gee ◽  
Alan T. Wall
Keyword(s):  
Noise Source ◽  
Near Field ◽  
Source Analysis ◽  
Acoustical Holography

scholarly journals An Improved Algorithm for Noise Source Localization Based on Equivalent Source Method

2016 ◽  
Vol 2016 ◽  
pp. 1-13
Author(s):  
Zhongming Xu ◽  
Qinghua Wang ◽  
Yansong He ◽  
Zhifei Zhang ◽  
Shu Li ◽  
...  
Keyword(s):  
Source Localization ◽  
High Frequency ◽  
Noise Source ◽  
Near Field ◽  
Low Frequency ◽  
Equivalent Source ◽  
Source Method ◽  
Functional Equivalent ◽  
Acoustical Holography ◽  
Equivalent Source Method

Near-field acoustical holography (NAH) based on the equivalent source method (ESM) is an efficient method applied for noise source identification. Asl2-norm-based regularization cannot produce a satisfactory solution of the ill-conditioned problem in high frequency, the conventional ESM is restricted to relatively low frequency, and the resolution of conventional ESM in middle to high frequency remains a limitation open to investigation. This article presents an algorithm known as improved functional equivalent source method (IFESM), designed to enhance the resolution of conventional ESM. This method is developed in the framework of wideband acoustical holography (WBH) combining with functional beamforming (FB). Through numerical simulations, it is proved that the proposed method can localize noise with higher resolution compared with WBH and conventional ESM, and the ghosts on noise source map can be suppressed effectively. The validity and the feasibility of the proposed method are manifested by experiments including single-source and coherent-source localization.

Military jet noise source imaging using multisource statistically optimized near-field acoustical holography

2016 ◽  
Vol 139 (4) ◽  
pp. 1938-1950 ◽  
Author(s):  
Alan T. Wall ◽  
Kent L. Gee ◽  
Tracianne B. Neilsen ◽  
Richard L. McKinley ◽  
Michael M. James
Keyword(s):  
Noise Source ◽  
Near Field ◽  
Jet Noise ◽  
Source Imaging ◽  
Acoustical Holography

scholarly journals Noise Source Identification and Noise Directivity Analysis of Bladeless Fans by Combined CFD and CAA Method

2020 ◽  
Author(s):  
Ang Li ◽  
Jun Chen ◽  
Yangfan Liu ◽  
J. Stuart Bolton ◽  
Patricia Davies
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Noise Source ◽  
Near Field ◽  
Low Noise ◽  
Pressure Level ◽  
Design Stage ◽  
Source Analysis ◽  
Far Field ◽  
Computational Domain

Abstract The bladeless fan is a new concept of fan that does not have visible impellers. It features low noise level, uniform airflow, and improved safety. It has been widely applied in household appliances. Since the customers are particularly sensitive to the noise generated by the fan, the aeroacoustics performance of the fan needs to be accurately characterized in the design stage. In this study, computational fluid dynamic (CFD) and computational aeroacoustics (CAA) are applied to investigate the aeroacoustics performance and identify the major noise source of the bladeless fan. A prototype of the bladeless fan, including a wind channel, a base cavity, a rotor and a stator inside the base, is set in a computational domain of 4m × 2m × 2m and the airflow through the fan is simulated. The hybrid mesh is generated, the unstructured mesh in the near field, and the structured at the far field. To compute the flow field, steady RANS simulation (standard k–ε turbulence model) and Large Eddy simulation (Smagorinsky-Lilly model) are carried out. Ffowcs Williams and Hawkings (FW-H) analogy is used to predict the acoustic field. Experiments, including air velocity measurement and sound pressure measurement, are conducted to validate simulation results. Sound pressure level results at the near-field receiver illustrate that the blade passage frequency can be captured by combined CFD and CAA method. Noise source analysis shows that the combination of the rotor and stator contributes most to the noise produced by the bladeless fan. The wind channel is the secondary source. Sound pressure level contours at different distances and different heights are generated to investigate the directivity pattern of the noise generated by the bladeless fan. At the near field, the produced noise at the front and the back of the bladeless fan are louder than those at left and right; at the far field, the noise at the front is much larger than the other three sides. In addition, at the near field, with the increase of the height, two separated hotspots appear over 2,500Hz and the sound pressure level at these two hotspots increases; at the far field, the noise distribution at different heights is similar and the peak near 3,000Hz can be estimated. A possible reason to cause this peak is vortex shedding at the trailing edge of the rotor’s blades. The aeroacoustics analysis is helpful to develop strategies to reduce noise and guide the improved design of the bladeless fan.

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.

Application of cylindrical near-field acoustical holography to the visualization of aeroacoustic sources

2003 ◽  
Vol 114 (2) ◽  
pp. 842-858 ◽  
Author(s):  
Moohyung Lee ◽  
J. Stuart Bolton ◽  
Luc Mongeau
Keyword(s):  
Near Field ◽  
Acoustical Holography

Near‐field acoustical holography in cylindrical spaces

1993 ◽  
Vol 94 (6) ◽  
pp. 3519-3519
Author(s):  
Charles J. Konzelman
Keyword(s):  
Near Field ◽  
Acoustical Holography
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