Airframe noise measurements on JAXA Jet Flying Test Bed “Hisho” using a phased microphone array

2017 ◽  
Vol 16 (4-5) ◽  
pp. 255-273 ◽  
Author(s):  
Takehisa Takaishi ◽  
Hiroki Ura ◽  
Kenichiro Nagai ◽  
Yuzuru Yokokawa ◽  
Mitsuhiro Murayama ◽  
...  
Keyword(s):  
Microphone Array ◽  
Low Frequency ◽  
Landing Gear ◽  
Frequency Resolution ◽  
Test Bed ◽  
Noise Sources ◽  
Low Frequencies ◽  
Airframe Noise ◽  
Noise Measurements ◽  
Wooden Platform

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.

Attenuation of Earmuffs against Low Frequency Noise

1987 ◽  
Vol 6 (4) ◽  
pp. 167-174 ◽  
Author(s):  
Jukka Starck ◽  
Jussi Pekkarinen ◽  
Seppo Aatola
Keyword(s):  
Low Frequency ◽  
Peak Level ◽  
Standard Test ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Low Frequencies ◽  
Hearing Protectors ◽  
Noise Measurements ◽  
Attenuation Values ◽  
Very High

The standard test for hearing protectors cannot be applied to determine the attenuation values for low frequency noise or for noise consisting of high intensity impulses. Moreover, the aging of earmuffs and the use of spectacles may cause leakage which decreases attenuation mainly at low frequencies. To study the real attenuation of earmuffs, noise measurements were taken outside and inside the earmuffs of workers at industrial work places, and of military conscripts when shooting with different firearms. The effect of spectacles on the attenuation was measured under laboratory conditions. In industrial workplaces the average attenuation was 4 dB in the 63 and 125 Hz octave bands. For shooting noise the attenuation was found to be good for small calibre weapons but poor for large calibre weapons, which generate very high peak level impulses at low frequencies. Spectacles decreased earmuff attenuation by 9–11 dB.

scholarly journals Application of MEMS Microphone Array Technology to Airframe Noise Measurements

2005 ◽  
Author(s):  
William Humphreys ◽  
Qamar Shams ◽  
Sharon Graves ◽  
Bradley Sealey ◽  
Scott Bartram ◽  
...  
Keyword(s):  
Microphone Array ◽  
Airframe Noise ◽  
Array Technology ◽  
Mems Microphone ◽  
Noise Measurements

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

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.

S0505-3-5 An Investigation on Airframe Noise Sources of Landing Gear Model

2009 ◽  
Vol 2009.2 (0) ◽  
pp. 269-270
Author(s):  
Hiroki URA ◽  
Yuzuru YOKOKAWA ◽  
Taro IMAMURA ◽  
Kazuomi YAMAMOTO
Keyword(s):  
Landing Gear ◽  
Noise Sources ◽  
Airframe Noise

A European study on landing gear airframe noise sources

2000 ◽  
Author(s):  
W. Dobrzynski ◽  
L. Chow ◽  
P. Guion ◽  
D. Shiells
Keyword(s):  
Landing Gear ◽  
European Study ◽  
Noise Sources ◽  
Airframe Noise

EXCESS LOW FREQUENCY NOISE IN SINGLE-WALL CARBON NANOTUBE

2006 ◽  
Vol 06 (01) ◽  
pp. L45-L55 ◽  
Author(s):  
S. SOLIVERES ◽  
A. HOFFMANN ◽  
F. PASCAL ◽  
C. DELSENY ◽  
M. S. KABIR ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Low Frequency ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Noise Sources ◽  
Single Wall Carbon Nanotube ◽  
Single Wall Carbon ◽  
Noise Measurements ◽  
Nanotube Defects

Low frequency noise measurements have been performed on a single-wall carbon nanotube connected by Ti/Au electrodes. It has been found that the 1/f noise decreases when the measurements are undertaken under vacuum and when the nanotube is partially degassed, showing a correlation between the fluctuation inducing the 1/f noise and the presence of gases. We show that the 1/f noise sources are located at the metal/nanotube contacts. When the device is annealed under vacuum at 450K, some Lorentzian shapes are observable and can be related to nanotube defects or to strongly bound molecules.

Effects of Vortex Generating Tabs on Noise Sources in an Ideally Expanded Mach 1.3 Jet

2003 ◽  
Vol 2 (1) ◽  
pp. 35-63 ◽  
Author(s):  
J. Hileman ◽  
M. Samimy
Keyword(s):  
Flow Visualization ◽  
Microphone Array ◽  
Pressure Ratio ◽  
Mixing Layer ◽  
Power Spectra ◽  
Acoustic Fields ◽  
Streamwise Vortices ◽  
Noise Sources ◽  
Noise Measurements ◽  
Generation Mechanisms

The flow and acoustic fields of an ideally expanded Mach 1.3 axisymmetric jet with delta tabs were examined to explore the effects of the tabs on noise sources. This work continues research that was performed on a baseline (no-tab) jet. Noise measurements were made at an angle of 30° to the downstream jet axis to allow a direct comparison to previous work, and to relate the sound generation mechanisms to the large structures that were visualized with temporally resolved flow visualization. Additional acoustic measurements were made at 60° and 90° locations. Three cases were examined: a baseline jet, a single delta tab jet, and a dual delta tab jet. Both tab jets were operated at the same pressure ratio as the baseline jet, which was ideally expanded. Power spectra and average acoustic waveform measurements were made for a variety of azimuthal locations; apparent noise origins were estimated with a 3-D microphone array; and temporally resolved flow visualization was used to examine the dynamic flow structure of the jet's mixing-layer. The results confirm that the tabs generate strong streamwise vortices that have a significant effect on both the flow and acoustic fields of the jet. The tabs cause significant deformation in the cross-stream plane of the mixing-layer, as well as regulating the formation and roll-up of vortices due to Kelvin Helmholtz instability. With the addition of tabs, the noise field becomes azimuthally dependent and the region of noise generation moves dramatically upstream. It appears that the tabs are directly responsible for an increase in noise over a range of Strouhal numbers between 0.8 and 2.5 through generated streamwise vortices and they are indirectly responsible for the modification of the noise generating mechanisms at Strouhal numbers below 0.6 through the induced spanwise vortex roll-ups.

Reliability Evaluation of 4H-SiC JFETs Using I-V Characteristics and Low Frequency Noise

2013 ◽  
Vol 740-742 ◽  
pp. 934-937
Author(s):  
Hua Khee Chan ◽  
Rupert C. Stevens ◽  
Jonathan P. Goss ◽  
Nicholas G. Wright ◽  
Alton B. Horsfall
Keyword(s):  
Spectral Density ◽  
Power Spectral Density ◽  
Low Frequency ◽  
Frequency Noise ◽  
Noise Power ◽  
Low Frequency Noise ◽  
Noise Sources ◽  
Noise Power Spectral Density ◽  
Power Spectral ◽  
Noise Measurements

Two sets of 4H-SiC signal-lateral JFETs were thermally aged at 400°C and 500°C in furnaces open to air for 1000 hours. I"-" V and low frequency noise measurements were performed on these devices and the results were compared against the as-fabricated sample. The data from I"-" V characterisation demonstrates that the linear and saturated drain-source current decreases monotonically with stress temperature. In addition, the linear characteristics of the JFETs have shifted approximately 1.5V along the drain-source voltage axis. Whilst the devices thermally aged at 400°C show no degradation in magnitude and behaviour in Noise Power Spectral Density (NPSD), the NPSD of 500°C stressed devices has increase approximately 30dB and it shows a full frequency spectrum of 1/ƒ dependency up to 100 kHz. A further investigation of the noise origin reveals that the Normalised Noise Power Spectral Density (NNPSD) of the aged sample is directly proportional to RDSwhich is similar to the as-fabricated sample. Thus we hypothesize that the existing noise sources have intensified possibly due to the evolution of defects.

Analysis of Low-Frequency Acoustic Sources in the Virginia Tech Stability Wind Tunnel

2017 ◽  
Author(s):  
W. Nathan Alexander ◽  
Christopher Hickling
Keyword(s):  
Wind Tunnel ◽  
Microphone Array ◽  
Low Frequency ◽  
Virginia Tech ◽  
Broadband Noise ◽  
Low Frequencies ◽  
Flow Speeds ◽  
Acoustic Sources ◽  
The Stability ◽  
Considerable Range

The Virginia Tech Stability Wind Tunnel is a unique low-speed facility with a Kevlar-walled test section developed for aeroacoustic measurements. A 251-channel configurable microphone array has been custom-designed for this facility to exploit the large available sensing area. Due to its large aperture, particularly for a laboratory scale instrument, the array has useful resolution down to very low frequencies, particularly in the streamwise direction. The considerable range of receiving angles and high number of sensors allows for direct measurement of source directivity. An experiment has been conducted in order to demonstrate the improved capability of the facility and investigate methods for the accurate measurement of acoustic sources at these low frequencies. Noise produced by a 50.8 mm diameter cylinder mounted in the Stability Wind Tunnel at flow speeds from 20 m/s to 60 m/s was measured. The cylinder produced shedding tones from 74 Hz to 212.5 Hz and measurable broadband noise and harmonics well beyond this. Delay and sum beamforming, deconvolution methods, and an inverse method are used to analyze the sound from the cylinder. When used in combination, these methods work well to identify the location of the source and reveal its changing directivity.

QLSA: A Software Library for Spectral Estimation in Low-Frequency Noise Measurement Applications

2019 ◽  
Vol 18 (02) ◽  
pp. 1940004 ◽  
Author(s):  
C. Ciofi ◽  
G. Scandurra ◽  
G. Giusi
Keyword(s):  
Spectral Analysis ◽  
Real Time ◽  
Spectral Estimation ◽  
Low Frequency ◽  
Frequency Resolution ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Software Library ◽  
Noise Measurements ◽  
Public Domain Software

A public domain software library is introduced and discussed that aims at enabling the development of customized real-time spectral analysis applications in the field of Low-Frequency Noise Measurements. Besides allowing spectral and cross-spectral estimation on multiple channels, the library effortlessly enables the implementation of quasi-logarithmic frequency resolution for real-time spectral analysis over several decades of frequency. By exploiting the library, the burden of the selection of the proper spectral estimation parameters in any given application is virtually eliminated.

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