On optimum impedance pattern for accurate wideband noise parameter characterization

2021 ◽  
Author(s):  
Mohammad M. Rahmati ◽  
Ali Banai
Keyword(s):  
Noise Parameter ◽  
Wideband Noise

Cryogenic Noise-Parameter Measurements: Recent Research and a Fully Automated Measurement Application

2021 ◽  
Vol 22 (8) ◽  
pp. 52-64
Author(s):  
Alexander Sheldon ◽  
Leonid Belostotski ◽  
Hamdi Mani ◽  
Christopher E. Groppi ◽  
Karl F. Warnick
Keyword(s):  
Automated Measurement ◽  
Noise Parameter

scholarly journals The influence of axial-flow fan trailing edge structure on internal flow

2018 ◽  
Vol 10 (11) ◽  
pp. 168781401881174
Author(s):  
Weijie Zhang ◽  
Jianping Yuan ◽  
Banglun Zhou ◽  
Hao Li ◽  
Ye Yuan
Keyword(s):  
Numerical Simulation ◽  
Low Frequency ◽  
Axial Flow ◽  
Internal Flow ◽  
Axial Flow Fan ◽  
Trailing Edge ◽  
Edge Structure ◽  
Blade Loading ◽  
Wideband Noise ◽  
Fluctuation Amplitude

Axial-flow fan with advantages such as large air volume, high head pressure, and low noise is commonly used in the work of air-conditioner outdoor unit. In order to investigate the internal flow mechanism of the axial-flow fan with different trailing edge structures of impellers, four kinds of impellers were designed, and numerical simulation and experiment were deployed in this article. The pressure distribution on the blades surface and distribution of vorticity in impellers were obtained using numerical simulation. Distribution of blade loading and velocity at the circumference are discussed. The relationship between the wideband noise and the trailing edge was established based on the experiment results. The results show that after the optimization of the trailing edge structure, the distribution of vorticity near the trailing edge of the blade is more uniform, especially at the trailing edge of 80% of the chord length of the suction surface. From the blade height position of 70% to the impeller tip, the pressure on the surface rapidly increases due to the tip vortex and the vortex shedding on the blade edge occurred in the top region of impeller. The pressure fluctuation amplitude at the trailing edge structure of the tail-edge optimization structure is smaller. In the distribution of blade loading, the three tail-edge optimization structures have smaller pressure fluctuations and pressure differences at the trailing edge structure. It is extremely important to control the fluctuation amplitude at the trailing edge. The amplitude of low-frequency sound pressure level of optimizing the trailing edge structure decreases obviously in the range of 50–125 Hz, and the optimization structure of trailing edge has an obvious effect on low-frequency wideband noise.

A new method for phemt noise-parameter determination based on 50-Ω noise measurement system

2003 ◽  
Vol 51 (10) ◽  
pp. 2079-2089 ◽  
Author(s):  
Jianjun Gao ◽  
Choi Look Law ◽  
Hong Wang ◽  
S. Aditya ◽  
G. Boeck
Keyword(s):  
Measurement System ◽  
Noise Measurement ◽  
New Method ◽  
Parameter Determination ◽  
Noise Parameter
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