A Comparison of Frequency-Domain Microphone Array Methods for the Characterization of Rotating Broadband Noise Sources

2019 ◽  
Vol 105 (1) ◽  
pp. 66-74 ◽  
Author(s):  
Christof Ocker ◽  
Gert Herold ◽  
Florian Krömer ◽  
Wolfram Pannert ◽  
Ennes Sarradj ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Microphone Array ◽  
Broadband Noise ◽  
Noise Sources

scholarly journals Localization and characterization of rotating noise sources on axial fans by means of an irregularly shaped microphone array

2021 ◽  
Vol 1909 (1) ◽  
pp. 012003
Author(s):  
O Amoiridis ◽  
R Zamponi ◽  
A Zarri ◽  
J Christophe ◽  
C Schram
Keyword(s):  
Microphone Array ◽  
Noise Sources ◽  
Axial Fans

scholarly journals Effect of a pylon on the broadband noise sources of counter-rotating turbomachinery

2021 ◽  
pp. 1475472X2110551
Author(s):  
Kristóf Tokaji ◽  
Csaba Horváth
Keyword(s):  
Noise Source ◽  
Microphone Array ◽  
Measurement Data ◽  
Leading Edge ◽  
Broadband Noise ◽  
Noise Sources ◽  
Noise Characteristics ◽  
Open Rotor ◽  
Blade Tip ◽  
Generation Mechanisms

Pylons are commonly used for the mounting of engines in the aircraft industry. On the other hand, the installation of a pylon influences the noise generation mechanisms and therefore alters the broadband noise characteristics of a given turbomachinery setup. In this investigation, a counter-rotating open rotor with and without a pylon is investigated in order to determine its effects on broadband noise sources. The various broadband noise sources and their typical frequency ranges have been determined using beamforming maps and spectral analysis. In order to attain a clear impression regarding the broadband noise sources, the Double Filtering beamforming method has been utilized in the investigation. This method removes the tonal components from the recorded signal of a microphone array, resulting in a purely broadband signal. Using beamforming maps, the dominant broadband noise source amplitudes and locations can therefore be investigated in great detail. Compared to other methods, the investigation of measurement data and beamforming maps helps determine the amplitude, the frequency range, and the significance of the various types of broadband noise sources that are truly present in the emitted noise. It has been found for lower frequencies, that the broadband noise sources at the blade root of the aft rotor are dominant, while for higher frequencies, the significant broadband noise sources are localized to the trailing edge region of the forward rotor and the leading edge of the aft rotor. The installation of a pylon has resulted in an additional broadband noise source appearing at the blade tip of the aft rotor.

scholarly journals Characterization of Noise Level Inside a Vehicle under Different Conditions

Sensors ◽  
2020 ◽  
Vol 20 (9) ◽  
pp. 2471 ◽  
Author(s):  
Daniel Flor ◽  
Danilo Pena ◽  
Luan Pena ◽  
Vicente A. de Sousa ◽  
Allan Martins
Keyword(s):  
Regression Analysis ◽  
Noise Level ◽  
Acoustic Noise ◽  
Experimental Setup ◽  
Strongly Correlated ◽  
Noise Levels ◽  
Noise Sources ◽  
Statistical Tools ◽  
Window Position

Vehicular acoustic noise evaluations are a concern of researchers due to health and comfort effects on humans and are fundamental for anyone interested in mitigating audio noise. This paper focuses on the evaluation of the noise level inside a vehicle by using statistical tools. First, an experimental setup was developed with microphones and a microcomputer located strategically on the car’s panel, and measurements were carried out with different conditions such as car window position, rain, traffic, and car speed. Regression analysis was performed to evaluate the similarity of the noise level from those conditions. Thus, we were able to discuss the relevance of the variables that contribute to the noise level inside a car. Finally, our results revealed that the car speed is strongly correlated to interior noise levels, suggesting the most relevant noise sources are in the vehicle itself.

Anomalous diffusion models in frequency-domain characterization of lithium-ion capacitors

2021 ◽  
Vol 490 ◽  
pp. 229332
Author(s):  
Shuang Song ◽  
Xiong Zhang ◽  
Chen Li ◽  
Kai Wang ◽  
Xianzhong Sun ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Anomalous Diffusion ◽  
Lithium Ion ◽  
Diffusion Models

scholarly journals Turbomachinery Noise Predictions: Present and Future

Acoustics ◽  
2019 ◽  
Vol 1 (1) ◽  
pp. 92-116 ◽  
Author(s):  
Stéphane Moreau
Keyword(s):  
Hybrid Methods ◽  
Free Field ◽  
Broadband Noise ◽  
Large Eddy Simulations ◽  
Analytical Models ◽  
Flat Plates ◽  
Tonal Noise ◽  
Noise Sources ◽  
Large Eddy ◽  
Rans Simulations

In future Ultra-High By-Pass Ratio turboengines, the turbomachinery noise (fan and turbine stages mainly) is expected to increase significantly. A review of analytical models and numerical methods to yield both tonal and broadband contributions of such noise sources is presented. The former rely on hybrid methods coupling gust response over very thin flat plates of finite chord length, either isolated or in cascade, and acoustic analogies in free-field and in a duct. The latter yields tonal noise with unsteady Reynolds-Averaged Navier–Stokes (u-RANS) simulations, and broadband noise with Large Eddy Simulations (LES). The analytical models are shown to provide good and fast first sound estimates at pre-design stages, and to easily separate the different noise sources. The u-RANS simulations are now able to give accurate estimates of tonal noise of the most complex asymmetric, heterogeneous fan-Outlet Guiding Vane (OGV) configurations. Wall-modeled LES on rescaled stage configurations have now been achieved on all components: a low-pressure compressor stage, a transonic high-pressure turbine stage and a fan-OGV configuration with good overall sound power level predictions for the latter. In this case, hybrid Lattice–Boltzmann/very large-eddy simulations also appear to be an excellent alternative to yield both contributions accurately at once.

Sign in / Sign up

Export Citation Format

Share Document