Noise reduction using a small-scale microphone array in multi noise source environment

2002 ◽  
Author(s):  
Akagi ◽  
Kago
Keyword(s):  
Noise Reduction ◽  
Noise Source ◽  
Microphone Array ◽  
Small Scale

scholarly journals COGENERATION UNIT NOISE REDUCTION BY ITS CASE

2021 ◽  
Vol 2021 (2) ◽  
pp. 4501-4504
Author(s):  
RADEK STRAMBERSKY ◽  
◽  
VACLAV PAVELKA ◽  
TOMAS PAWLENKA ◽  
PAVEL SURANEK ◽  
...  
Keyword(s):  
Noise Reduction ◽  
Frequency Spectrum ◽  
Noise Source ◽  
Microphone Array ◽  
Noise Measurement ◽  
Sound Power ◽  
Final Number ◽  
Beamforming Algorithm

This paper deals with cogeneration unit noise measurement by the acoustic camera. Noise is not only measured as the final number of sound power levels, but also its original location is determined with the use of the beamforming algorithm. The properties of the used microphone array are considered and numerically calculated as every different microphone array layout will measure with another resolution. From the frequency spectrum, the possible technical source is determined. The results of noise source visualization show the cogeneration unit case noise decreasing effect while also offering the possibilities for design improvements.

scholarly journals Aeroacoustic noise reduction by application of end plates on wall-mounted finite airfoils

2021 ◽  
Vol 62 (5) ◽  
Author(s):  
Erik Schneehagen ◽  
Thomas F. Geyer ◽  
Ennes Sarradj ◽  
Danielle J. Moreau
Keyword(s):  
Noise Reduction ◽  
Microphone Array ◽  
Boundary Layer Transition ◽  
Tip Vortex ◽  
Layer Transition ◽  
Aeroacoustic Noise ◽  
End Plate ◽  
Array Measurements ◽  
Field Noise ◽  
Naca 0012

Abstract One known method to reduce vortex shedding from the tip of a blade is the use of end plates or winglets. Although the aerodynamic impact of such end plates has been investigated in the past, no studies exist on the effect of such end plates on the far-field noise. The aeroacoustic noise reduction of three different end-plate geometries is experimentally investigated. The end plates are applied to the free end of a wall-mounted symmetric NACA 0012 airfoil and a cambered NACA 4412 airfoil with an aspect ratio of 2 and natural boundary layer transition. Microphone array measurements are taken in the aeroacoustic open-jet wind tunnel at BTU Cottbus-Senftenberg for chord-based Reynolds numbers between 75,000 and 225,000 and angles of attack from 0$$^\circ$$ ∘ to 30$$^\circ$$ ∘ . The obtained acoustic spectra show a broad frequency hump for the airfoil base configurations at higher angles of attack that is attributed to tip noise. Hot-wire measurements taken for one configuration show that the application of an end plate diffuses the vorticity at the tip. The aeroacoustic noise contribution of the tip can be reduced when the endplates are applied. This reduction is most effective for higher angles of attack, when the tip vortex is the dominant sound source. Graphic abstract

Design and optimization of acoustic liners with a shear grazing flow: OPAL software platform applications

2021 ◽  
Vol 263 (6) ◽  
pp. 152-163
Author(s):  
Remi Roncen ◽  
Pierre Vuillemin ◽  
Patricia Klotz ◽  
Frank Simon ◽  
Fabien Méry ◽  
...  
Keyword(s):  
Noise Reduction ◽  
Low Frequency ◽  
Small Scale ◽  
Software Platform ◽  
Total Size ◽  
Linearized Euler Equations ◽  
Design And Optimization ◽  
Acoustic Liners ◽  
Frequency Regime ◽  
Grazing Flow

In the context of noise reduction in diverse applications where a shear grazing flow is present (i.e., engine nacelle, jet pump, landing gear), improved acoustic liner solutions are being sought. This is particularly true in the low-frequency regime, where space constraints currently limit the efficiency of classic liner technology. To perform the required multi-objective optimization of complex meta-surface liner candidates, a software platform called OPAL was developed. Its first goal is to allow the user to assemble a large panel of parallel/serial assembly of unit acoustic elements, including the recent concept of LEONAR materials. Then, the physical properties of this liner can be optimized, relatively to given weighted objectives (noise reduction, total size of the sample, weight), for a given configuration. Alternatively, properties such as the different impedances of liner unit surfaces can be optimized. To accelerate the process, different nested levels of optimization are considered, from 0D analytical coarse designs in order to reduce the parameter space, up to 2D plan or axisymmetric high-order Discontinuous Galerkin resolution of the Linearized Euler Equations. The presentation will focus on the different aspects of liner design considered in OPAL, and present an application on different samples made for a small scale aeroacoustic bench.

Wavepacket noise source model for microphone array data analysis of hot supersonic jets

2013 ◽  
Vol 134 (5) ◽  
pp. 4127-4127 ◽  
Author(s):  
Philip Morris ◽  
Robert Dougherty ◽  
Chris Nelson ◽  
Alan Cain ◽  
Kenneth Brentner
Keyword(s):  
Data Analysis ◽  
Noise Source ◽  
Microphone Array ◽  
Source Model ◽  
Supersonic Jets ◽  
Array Data

Study of Microphone Array for Noise Reduction in Sound Based Micro-Tool Wear Monitoring

2011 ◽  
Author(s):  
Chi-Feng Huang ◽  
Ming-Chyuan Lu
Keyword(s):  
Noise Reduction ◽  
Monitoring System ◽  
Background Noise ◽  
Filter Design ◽  
Microphone Array ◽  
Wiener Filter ◽  
Cutting Condition ◽  
Tool Condition ◽  
Micro Tool ◽  
Condition Monitoring System

An experienced technician can usually identify the cutting condition by hearing the sound generated during the cutting and the sound signal can be expected to detect the features closely related to the tool condition. However, the background noise always contaminates the signal obtained by microphone system during cutting and reduces the chance of applying the sound based micro tool condition monitoring system in industry. In order to reduce the noise effect and improve the system performance, a microphone array integrated with Wiener filter was designed and implemented in this study to enhance the noise reduction capability for monitoring system. The experimental results show that the microphone array integrated with Wiener filter provides a better solution than single microphone integrated with Wiener filter or the microphone array without the post filter design in reducing the broadband background noise.

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