Summary of Noise Reduction Characteristics of Typical General Aviation Materials

1979 ◽  
Author(s):  
J. Roskam ◽  
F. Grosveld ◽  
J. Van Aken
Keyword(s):  
Noise Reduction ◽  
General Aviation ◽  
Reduction Characteristics

On the reductions of aerofoil-turbulence interaction noise through multi-wavelength leading edge serrations

2020 ◽  
pp. 095441002096574
Author(s):  
S Narayanan ◽  
Sushil Kumar Singh
Keyword(s):  
Noise Reduction ◽  
Maximum Amplitude ◽  
Leading Edge ◽  
Emission Angle ◽  
Broadband Noise ◽  
Dual Wavelength ◽  
Flat Plates ◽  
Wide Range ◽  
Multi Wavelength ◽  
Reduction Characteristics

This paper provides an experimental study into the use of multi-wavelength sinusoidal leading edge ( LE) serrations for enhancing the aerofoil-broadband noise reductions. The noise reduction performances of multi-wavelength serration profiles introduced on a flat plate are compared against those generated by single-wavelength profiles when applied separately. The multi-wavelength leading edge serration is made in such a way that its maximum amplitude is kept same as that of each single-wavelength ones to be compared. The present study reveals that the dual-wavelength serrations provide higher noise reductions over a narrow band of frequencies as compared to single and triple wavelength ones. Further, it reveals that the noise reduction characteristics of dual-wavelength serrated airfoils are similar to the flat plates. It shows that the baseline plate generate higher noise radiations for all emission angles as compared to leading edge serrated plates, but the common feature among them is the downstream directivity. For the range of frequencies 0.9 to 5 kHz, the highest directivity is seen at an emission angle of 55° for the baseline, while it occurs at 75° for the serrated plates. The dual wavelength serrations generate lowest acoustic radiations as compared to single and triple ones for all the emission angles. Also, it is noticed that the radiation levels of the dual serrations decrease with increase in amplitude of the serration, which shows that the longer dual serrations generate lowest acoustic radiations. Thus, the present study illustrates that the dual wavelength leading edge serrations act as the best passively modified serration profiles for achieving the highest noise reductions over a wide range of frequencies as compared to single and triple wavelength ones.

401 Noise Reduction Characteristics of Noise Canceling in a Sound Field Environment

2014 ◽  
Vol 2014.63 (0) ◽  
pp. _401-1_-_401-2_
Author(s):  
Kazutaka ASAMOTO ◽  
Isao ITO ◽  
Takumi HATAOKA ◽  
Katumi MORIWAKI
Keyword(s):  
Noise Reduction ◽  
Sound Field ◽  
Field Environment ◽  
Reduction Characteristics ◽  
Noise Canceling

The Effect of Active Noise Reduction Technology on Noise Induced Pilot Fatigue and Associated Cognitive Performance Decrements

1996 ◽  
Vol 40 (2) ◽  
pp. 67-71 ◽  
Author(s):  
John Jordan ◽  
Wayne C. Harris ◽  
Phillip N. Goernert ◽  
John Roberts
Keyword(s):  
Noise Reduction ◽  
Cognitive Performance ◽  
General Aviation ◽  
Flight Instruction ◽  
Active Noise ◽  
Subjective Fatigue ◽  
Flight Instructors ◽  
Active Noise Reduction ◽  
Pilot Fatigue

Fatigue in the general aviation cockpit is caused by a variety of factors including cockpit noise. Active Noise Reduction (ANR) headsets have been proposed as a method to decrease cockpit noise and thereby decrease fatigue and the cognitive performance decrements associated with fatigue. The present study contrasted the subjective fatigue and cognitive performance of Certified Flight Instructors (CFI) during a day of in-air flight instruction with ANR headsets versus conventional headsets. CFIs exhibited increased subjective fatigue and a pattern of more rapid but less accurate cognitive performance at the end of an instructional day. However, subjective fatigue and cognitive performance changes did not differ as a function of type of headset worn. The results suggest that subjective fatigue increases and cognitive performance changes occur during a day of flying but they provide no evidence that the use of ANR headsets modify these changes.

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