Band Transition Noise Measurements of Gas Discharge Noise Sources (Correspondence)

In 2015, the Japan Aerospace Exploration Agency launched the Flight demonstration of QUiet technology to Reduce nOise from High-lift configurations project to verify by flight demonstration the feasibility of practical noise-reducing aircraft modification concepts. In order to serve as a baseline for comparison before modification, airframe noise sources of the JAXA Jet Flying Test Bed “Hisho” were measured with a 30 m diameter array of 195 microphones mounted on a wooden platform built temporary beside the runway of Noto Satoyama Airport in Japan. A classical Delay and Sum in the time domain beamforming algorithm was adapted for the present study, with weight factors introduced to improve the low-frequency resolution and autocorrelations eliminated to suppress wind noise at high frequencies. In the landing configuration at idle thrust, the main landing gear, nose landing gear, and side edges of the six extended flap panels were found to be the dominant “Hisho” airframe noise sources. Deconvolution by the DAMAS and CLEAN-SC algorithms provided clearer positions of these sound sources at low frequencies. Integration of acoustical maps agreed well with the sound pressure level measured by a microphone placed at the center of the microphone array and gave detailed information about the contribution of each noise source.

Download Full-text

Separation of Individual Noise Sources from Compound Noise Measurements in Digital Circuits

APCCAS 2006 - 2006 IEEE Asia Pacific Conference on Circuits and Systems ◽

10.1109/apccas.2006.342070 ◽

2006 ◽

Author(s):

Vivek P. Nigam ◽

Masud H. Chowdhury ◽

Roland Priemer

Keyword(s):

Digital Circuits ◽

Noise Sources ◽

Noise Measurements

Download Full-text

SCLC Degradation in 980 nm Pump Laser by Using Electrical Noise

ISRN Optics ◽

10.5402/2012/841695 ◽

2012 ◽

Vol 2012 ◽

pp. 1-4

Author(s):

B. Orsal ◽

I. Asaad

Keyword(s):

Defect Density ◽

Optical Power ◽

Longitudinal Mode ◽

Pump Laser ◽

Electrical Noise ◽

Noise Sources ◽

Noise Spectral Density ◽

Noise Current ◽

Noise Measurements ◽

Pump Lasers

The knowledge of the noise levels is important for pump laser diodes as it allows to study and to locate the noise sources and their origin. 980 nm fresh and aged pump lasers have been characterized by using electrical noise measurements. At 10 Hz, the spectra are dominated by () noise. Current noise spectral density (CNSD) is dominated by (). The trapping defect density near the n+n- and p+p- interfaces is related to pinching of the space-charge-limited current (SCLC) effect. An excess electrical noise due to longitudinal mode hopping is correlated with optical power fluctuations.

Download Full-text

Internally Generated Noise From Gas Turbine Engines. Measurement and Prediction

Journal of Engineering for Power ◽

10.1115/1.3616636 ◽

1967 ◽

Vol 89 (2) ◽

pp. 177-185 ◽

Cited By ~ 9

Author(s):

M. J. T. Smith ◽

M. E. House

Keyword(s):

Gas Turbine ◽

Full Scale ◽

Turbine Engines ◽

Gas Turbine Engines ◽

Test Results ◽

Radiation Patterns ◽

Noise Sources ◽

Prediction Technique ◽

Noise Measurements ◽

Engine Compressor

The noise sources from gas turbine engines are defined and their radiation patterns identified from test results. Examination of single-stage and full-scale engine compressor noise measurements leads to a prediction technique being evolved for inlet and efflux levels.

Download Full-text