A single chip broadband noise source for noise measurements at cryogenic temperatures

For high speed trains running at 300km/h or more, the aerodynamic noise becomes the primary noise source. A good knowledge of the location, spectral characteristics and propagation behavior of the noise source and the corresponding methods to reduce the effect of the aerodynamic noise are of crucial necessity during the design process of the high speed train. Based on the Lighthill Analogy, the pressure fluctuation of air at the surface of the train is acquired by simulating the flow field of a CRH3 high speed train running at 200 km/h, 300 km/h, 400 km/h and 500km/h by means of large eddy simulation method. By Fourier transformation, the distribution and the spectral characteristics of the surface acoustic dipole sources are obtained. The analysis of the results shows that the aerodynamic noise of the high speed train is a broadband noise with a strong radiation power band from 50Hz to 1000Hz. The dipole acoustic power calculated by statistically averaged on train surface is found to be proportional to the sixth power of running speed of the high speed train. The first and second bogie, the inter-car gap, the air deflector of the power train and the train nose of the last wagon are the main noise sources that contain high radiation energy.

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Noise assessment of taxibotted versus conventional taxiing operations using a phased microphone array

INTER-NOISE and NOISE-CON Congress and Conference Proceedings ◽

10.3397/in-2021-1765 ◽

2021 ◽

Vol 263 (5) ◽

pp. 1152-1163

Author(s):

Bieke von den Hoff ◽

Mirjam Snellen ◽

Dick G. Simons

Keyword(s):

Noise Source ◽

Microphone Array ◽

Noise Levels ◽

Noise Sources ◽

Operational Testing ◽

Electric Aircraft ◽

Noise Source Identification ◽

Noise Measurements ◽

Noise Assessment ◽

Lower Noise

In sustainable aviation the focus is mostly applied to the greenhouse gas emissions during flight. However airports have an increasing interest in reducing emissions during ground operations such as taxiing for example to improve the local air quality. Amsterdam Airport Schiphol started a pilot for sustainable taxiing with a pilot-controlled hybrid-electric aircraft towing vehicle called TaxiBot in 2020. The COVID-19 pandemic created an opportunity for extensive operational testing on a near-empty airport. Due to the low background noise levels in this situation, also a noise assessment of taxiing with the TaxiBot versus conventional two-engine taxiing was performed. This assessment can be used to evaluate the noise levels to which ground workers or neighbouring communities are exposed due to TaxiBot operations. For the noise measurements a phased microphone array was used, which allowed not only for a noise level and directionality assessment, but also for noise source identification. This paper compares the noise emissions and noise sources between a taxibotted and conventional taxiing operation. The results show that a taxibotted taxiing operation produces significantly lower noise levels. Additionally, acoustic imaging shows that the TaxiBot engine is the main noise source for a taxibotted pass-by manoeuvre.

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New Procedure for Noise Source Mapping During Pass-By Noise Measurements

10.4271/2003-01-3734 ◽

2003 ◽

Author(s):

Alun Crewe ◽

Florent Perrin ◽

Gene Smiley ◽

Vincent Benoit ◽

Karim Haddad

Keyword(s):

Noise Source ◽

Noise Measurements

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CFD Analysis of Journal Bearing with a Heterogeneous Rough/Smooth Surface

Lubricants ◽

10.3390/lubricants9090088 ◽

2021 ◽

Vol 9 (9) ◽

pp. 88

Author(s):

Mohammad Tauviqirrahman ◽

J. Jamari ◽

Arjuno Aryo Wicaksono ◽

M. Muchammad ◽

S. Susilowati ◽

...

Keyword(s):

Journal Bearing ◽

Noise Source ◽

Journal Bearings ◽

Broadband Noise ◽

Load Carrying Capacity ◽

Computational Investigation ◽

Roughness Model ◽

Load Carrying ◽

Cfd Method ◽

Lower Noise

In the present study, a computational investigation into acoustic and tribological performances in journal bearings is presented. A heterogeneous pattern, in which a rough surface is engineered in certain regions and is absent in others, is employed to the bearing surface. The roughness is assumed to follow the sand-grain roughness model, while the bearing noise is solved based on broadband noise source theory. Three types of heterogeneous rough/smooth journal bearings exhibiting different placement and number of the rough zone are evaluated at different combinations of eccentricity ratio using the CFD method. Numerical results show that the heterogeneous rough/smooth bearings can supply lower noise and larger load-carrying capacity in comparison with conventional bearings. Moreover, the effect on the friction force is also discussed.

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