Pile driving noise: Source level and sound generation mechanisms.

2011 ◽  
Vol 129 (4) ◽  
pp. 2461-2461
Author(s):  
Christ A. F. de Jong ◽  
Mario Zampolli ◽  
Michael A. Ainslie ◽  
Erwin W. Jansen ◽  
Laurent Fillinger ◽  
...  
Keyword(s):  
Noise Source ◽  
Pile Driving ◽  
Sound Generation ◽  
Source Level ◽  
Generation Mechanisms

scholarly journals Estimation of the Noise Source Level of a Commercial Ship Using On-Board Pressure Sensors

2021 ◽  
Vol 11 (3) ◽  
pp. 1243
Author(s):  
Hongseok Jeong ◽  
Jeung-Hoon Lee ◽  
Yong-Hyun Kim ◽  
Hanshin Seol
Keyword(s):  
Noise Source ◽  
Pressure Sensors ◽  
Low Frequency ◽  
Frequency Resolution ◽  
Source Strength ◽  
Recording Time ◽  
Source Level ◽  
The One ◽  
Hydrophone Array ◽  
Good Agreement

The dominant underwater noise source of a ship is known to be propeller cavitation. Recently, attempts have been made to quantify the source strength using on-board pressure sensors near the propeller, as this has advantages over conventional noise measurement. In this study, a beamforming method was used to estimate the source strength of a cavitating propeller. The method was validated against a model-scale measurement in a cavitation tunnel, which showed good agreement between the measured and estimated source levels. The method was also applied to a full-scale measurement, in which the source level was measured using an external hydrophone array. The estimated source level using the hull pressure sensors showed good agreement with the measured one above 400 Hz, which shows potential for noise monitoring using on-board sensors. A parametric study was carried out to check the practicality of the method. From the results, it was shown that a sufficient recording time is required to obtain a consistent level at high frequencies. Changing the frequency resolution had little effect on the result, as long as enough data were provided for the one-third octave band conversion. The number of sensors affected the mid- to low-frequency data.

A Method for Noise Source Levels Inversion with Underwater Ambient Noise Generated by Typhoon in Deep Ocean

2018 ◽  
Vol 26 (02) ◽  
pp. 1850007 ◽  
Author(s):  
Qiulong Yang ◽  
Kunde Yang ◽  
Shunli Duan
Keyword(s):  
Ambient Noise ◽  
Noise Source ◽  
Surface Wind ◽  
Deep Ocean ◽  
Noise Sources ◽  
Noise Field ◽  
Sea Surface Wind ◽  
Source Level ◽  
The Western Pacific ◽  
Good Agreement

Sea-surface wind agitation can be considered the dominant noise sources whose intensity relies on local wind speed during typhoon period. Noise source levels in previous researches may be unappreciated for all oceanic regions and should be corrected for modeling typhoon-generated ambient noise fields in deep ocean. This work describes the inversion of wind-driven noise source level based on a noise field model and experimental measurements, and the verification of the inverted noise source levels with experimental results during typhoon period. A method based on ray approach is presented for modeling underwater ambient noise fields generated by typhoons in deep ocean. Besides, acoustic field reciprocity is utilized to decrease the calculation amount in modeling ambient noise field. What is more, the depth dependence and the vertical directionality of noise field based on the modeling method and the Holland typhoon model are evaluated and analyzed in deep ocean. Furthermore, typhoons named “Soulik” in 2013 and “Nida” in 2016 passed by the receivers deployed in the western Pacific (WP) and the South China Sea (SCS). Variations in sound speed profile, bathymetry, and the related oceanic meteorological parameters are analyzed and taken into consideration for modeling noise field. Boundary constraint simulated annealing (SA) method is utilized to invert the three parameters of noise source levels and to minimize the objective function value. The prediction results with the inverted noise source levels exhibit good agreement with the measured experiment data and are compared with predicted results with other noise sources levels derived in previous researches.

DNS of a plane mixing layer for the investigation of sound generation mechanisms

2008 ◽  
Vol 37 (4) ◽  
pp. 360-368 ◽  
Author(s):  
Andreas Babucke ◽  
Markus Kloker ◽  
Ulrich Rist
Keyword(s):  
Mixing Layer ◽  
Sound Generation ◽  
Plane Mixing Layer ◽  
Generation Mechanisms

scholarly journals Computational Acoustic Beamforming for Noise Source Identification for Small Wind Turbines

2017 ◽  
Vol 2017 ◽  
pp. 1-24
Author(s):  
Ping Ma ◽  
Fue-Sang Lien ◽  
Eugene Yee
Keyword(s):  
Wind Turbine ◽  
Noise Source ◽  
Sound Generation ◽  
Noise Sources ◽  
Wind Turbine Noise ◽  
Trailing Edge Noise ◽  
Small Wind Turbine ◽  
Small Wind Turbines ◽  
Noise Source Identification ◽  
Naca 0012

This paper develops a computational acoustic beamforming (CAB) methodology for identification of sources of small wind turbine noise. This methodology is validated using the case of the NACA 0012 airfoil trailing edge noise. For this validation case, the predicted acoustic maps were in excellent conformance with the results of the measurements obtained from the acoustic beamforming experiment. Following this validation study, the CAB methodology was applied to the identification of noise sources generated by a commercial small wind turbine. The simulated acoustic maps revealed that the blade tower interaction and the wind turbine nacelle were the two primary mechanisms for sound generation for this small wind turbine at frequencies between 100 and 630 Hz.

COMPUTATIONAL AEROACOUSTICS EXAMPLES SHOWING THE FAILURE OF THE ACOUSTIC ANALOGY THEORY TO IDENTIFY THE CORRECT NOISE SOURCES

2002 ◽  
Vol 10 (04) ◽  
pp. 387-405 ◽  
Author(s):  
CHRISTOPHER K. W. TAM
Keyword(s):  
Noise Source ◽  
Scaling Law ◽  
Sound Generation ◽  
Acoustic Analogy ◽  
Noise Sources ◽  
Instability Waves ◽  
Full Wave ◽  
Applied Mathematician ◽  
Misleading Interpretation ◽  
Dominant Theory

Lighthill's Acoustic Analogy has been the dominant theory of aeroacoustics, especially jet aeroacoustics for almost fifty years. As yet, except for the u8 scaling law, which was derived by dimensional analysis, jet noise prediction based on the Acoustic Analogy approach has not been particularly successful. This paper examines some of the weaknesses and ambiguities in the formulation of the Acoustic Analogy theories. It is concluded that if the analogy is carried out completely, in the sense that the full wave propagation terms are retained in the propagation part of the equations of the analogy, then the theory offers no sensible noise source terms. To demonstrate that the Acoustic Analogy can fail to identify the correct noise sources, four examples are considered. They include an initial value problem, a boundary problem, the problem of weak solution and the problem of sound generation by instability waves in jets and mixing layers. These examples show clearly how, in each case, the Acoustic Analogy theory identifies the wrong noise source. Indeed, the Acoustic Analogy could provide, if not careful, misleading interpretation of the physics of sound generation. This paper is dedicated to Professor David G. Crighton, outstanding applied mathematician, world famous acoustician and a much respected friend.

scholarly journals Derivation of Lighthill’s Eighth Power Law of an Aeroacoustic Quadrupole in Acoustic Spacetime

Acoustics ◽  
2020 ◽  
Vol 2 (3) ◽  
pp. 666-673
Author(s):  
Drasko Masovic ◽  
Ennes Sarradj
Keyword(s):  
Power Law ◽  
Sound Propagation ◽  
Dimensional Manifold ◽  
Sound Waves ◽  
Sound Generation ◽  
Speed Of Light ◽  
Acoustic Analogy ◽  
Analytical Treatment ◽  
Weak Perturbation ◽  
Generation Mechanisms

Acoustic spacetime is a four-dimensional manifold analogue to the relativistic spacetime with the reference speed of light replaced by the speed of sound. It has been established primarily for the indirect studies of relativistic phenomena by means of their better understood acoustic analogues. More recently, it has also been used for the analytical treatment of sound propagation in various uniform and non-uniform flows of the background fluid. In this paper the analogy is extended and utilized to derive Lighthill’s eight power law for sound generation of an aeroacoustic quadrupole. Adding to the existing analogue theory, propagating sound waves are described in terms of a weak perturbation of the background acoustic spacetime metric. The obtained result proves that the acoustic analogy can be extended to cover both weak perturbation of the fluid due to the sound waves and certain sound generation mechanisms, at least in incompressible low Mach number flows.

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