Optimization of underdetermined hologram points in reconstructing the vibro-acoustic source field based on ESM

2021 ◽  
Vol 263 (5) ◽  
pp. 1683-1687
Author(s):  
Laixu Jiang ◽  
Jeong-Guon Ih
Keyword(s):  
Near Field ◽  
Distance Measurement ◽  
Iteration Step ◽  
Test Results ◽  
Acoustic Source ◽  
Sound Sources ◽  
Optimal Arrangement ◽  
Measuring Point ◽  
Source Field ◽  
Value Decomposition

The distribution of measurement points is important in reconstructing the vibro-acoustic source field using the near-field acoustical holography (NAH) based on the equivalent source method (ESM). Because too close measurement impose a limit in the implementation of ESM, an optimal arrangement of the hologram data is needed to enable a longer distance measurement although the points are still within the near field. In this work, the optimal measurement positions are determined by adopting the method that assures the independence among the measuring positions as far as possible. Singular value decomposition of the transfer matrix is employed in the loop-iteration calculation fashion, in which the candidate measuring point affecting the increase of singularity is eliminated at each iteration step. Comparison is made with the uniformly distributed hologram points, the monopole version of ESM model, and the patch holography method. The test results reveal that the acoustic field of sound sources can be reconstructed meaningfully from the optimized hologram points of underdetermined condition. Under the predetermined reconstruction accuracy, the test results varying the hologram distance show that it is possible to realize the underdetermined far-distance measurement than the usual NAH.

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.

Study on the Properties of Aerodynamic Reference Sound Sources

2019 ◽  
Vol 105 (6) ◽  
pp. 960-969 ◽  
Author(s):  
Spyros Brezas ◽  
Volker Wittstock
Keyword(s):  
Ambient Temperature ◽  
Atmospheric Pressure ◽  
Rotation Speed ◽  
Near Field ◽  
Sound Power ◽  
Sound Sources ◽  
The Core ◽  
In Situ Conditions ◽  
Calibration Condition

Towards the establishment of traceability in sound power in airborne sound, the present study focuses on the dissemination procedure. Aerodynamic reference sound sources were studied as potential transfer standards. Initially, the sources were examined in the up-to-present requirements. The core of the study is the correction required for the transition from calibration to in situ conditions. The influence of atmospheric pressure, ambient temperature and fan rotation speed was investigated and the corresponding correction was determined. A comparison to an existing correction was also performed. Near field effects were another part of the study. The related uncertainty was estimated in a transparent approach. The dependency of the uncertainty on the in situ and calibration condition values is also presented.

scholarly journals Modeling the Influence of Dust-Removing Extraction Fan’S Parameters on the Dust Control Effects in the Tunnel

2016 ◽  
Vol 5 (2) ◽  
pp. 18 ◽  
Author(s):  
Qingguo Wang ◽  
Deming Wang ◽  
Hetang Wang
Keyword(s):  
Cfd Simulation ◽  
Dust Control ◽  
Test Results ◽  
Ventilation Mode ◽  
Forced Ventilation ◽  
Migration Process ◽  
Optimal Arrangement ◽  
Air Supply ◽  
Mechanized Tunnelling ◽  
Migration Law

<p class="emsd"><a name="OLE_LINK1"></a><span lang="EN-GB">In the process of comprehensive mechanized tunnelling in coal mines, forced ventilation is usually adopted to supply air in China. But this ventilation mode could cause the dust rise and diffuse more easily, which has threaten the mine workers’ health seriously. To solve this problem, </span><a name="OLE_LINK8"></a><span lang="EN-GB">dust-removing extraction fan</span><span lang="EN-GB"> is generally used to suck and purify dusty air in mines. However, the optimal arrangement scheme for dust control is rarely systematically studied. In this paper, we took the tunnel in Donghuantuo Mine as an example and use CFD simulation technology to analyze the dust migration law and dust control effects under different conditions. An unsteady state solution is used to simulate the process and the simulation have realized the visualization of dust migration process with time and the results are as follows. Firstly, it’s better for dust control to <a name="OLE_LINK15"></a>arrange the inlet of the dust-removing extraction fan to the air return side rather than to the center of the tunnel. Secondly, the dust control effects decrease with the distance between inlet of the dust-removing extraction fan and heading face increases. Thirdly, as the amount of air suction is larger than air supply, the dust control efforts would get worse. Field test results are similar <a name="OLE_LINK9"></a>with that obtained from simulation under the optimal arrangement, which proves the reliability of simulation.</span></p>

scholarly journals The overlapping roles of the inner ear and lateral line: the active space of dipole source detection

2000 ◽  
Vol 355 (1401) ◽  
pp. 1115-1119 ◽  
Author(s):  
Christopher B. Braun ◽  
Sheryl Coombs
Keyword(s):  
Inner Ear ◽  
Lateral Line ◽  
Near Field ◽  
Dipole Source ◽  
Source Detection ◽  
Sound Sources ◽  
Distance Range ◽  
Spatial Gradients ◽  
Theoretical Predictions ◽  
Benthic Fishes

The problems associated with the detection of sounds and other mechanical disturbances in the aquatic environment differ greatly from those associated with airborne sounds. The differences are primarily due to the incompressibility of water and the corresponding increase in importance of the acoustic near field. The near field, or hydrodynamic field, is characterized by steep spatial gradients in pressure, and detection of the accelerations associated with these gradients is performed by both the inner ear and the lateral line systems of fishes. Acceleration–sensitive otolithic organs are present in all fishes and provide these animals with a form of inertial audition. The detection of pressure gradients, by both the lateral line and inner ear, is the taxonomically most widespread mechanism of sound–source detection amongst vertebrates, and is thus the most likely primitive mode of detecting sound sources. Surprisingly, little is known about the capabilities of either the lateral line or the otolithic endorgan in the detection of vibratory dipole sources. Theoretical considerations for the overlapping roles of the inner ear and lateral line systems in midwater predict that the lateral line will operate over a shorter distance range than the inner ear, although with a much greater spatial resolution. Our empirical results of dipole detection by mottled sculpin, a benthic fish, do not agree with theoretical predictions based on midwater fishes, in that the distance ranges of the two systems appear to be approximately equal. This is almost certainly as a result of physical coupling between the fishes and the substrate. Thus, rather than having a greater active range, the inner ear appears to have a reduced distance range in benthic fishes, and the lateral line distance range may be concomitantly extended.

Sound Source Identification and Acoustic Contribution Analysis Using Nearfield Acoustic Holography

2014 ◽  
Vol 945-949 ◽  
pp. 717-724 ◽  
Author(s):  
Jiang Hua Deng ◽  
Jun Hong Dong ◽  
Guang De Meng
Keyword(s):  
Source Identification ◽  
Noise Source ◽  
Near Field ◽  
Superposition Principle ◽  
Sound Field ◽  
Mirror Image ◽  
Sound Sources ◽  
Incoming Wave ◽  
Reflected Waves ◽  
Acoustic Contribution

The main goal of the present paper is to provide a method of source identification. Firstly, statistically optimal near-field acoustical holography (SONAH) techniques are applied to locate sound sources with the reflected sound field. In the presence of reflection plane parallel and perpendicular to the source plane, the incoming wave and reflected waves are separated based on the acoustic superposition principle and acoustic mirror image principle to satisfy the condition of the sound sources reconstruction using SONAH. Secondly, contribution of noise source to the special field point is analyzed and noise source ranking of interior panel groups are evaluated based the proposed three step acoustic contribution method. Finally, this method is verified experimentally.

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