scholarly journals Noise Reduction Potential of Cellular Metals

Metals ◽  
2012 ◽  
Vol 2 (2) ◽  
pp. 195-201 ◽  
Author(s):  
Björn Hinze ◽  
Joachim Rösler ◽  
Nicolas Lippitz
Keyword(s):  
Noise Reduction ◽  
Reduction Potential ◽  
Cellular Metals

scholarly journals Noise Reduction Potential for the Existing Business Jet Fleet

1977 ◽  
Author(s):  
W. J. Galloway ◽  
J. F. Wilby ◽  
H. C. True
Keyword(s):  
Noise Reduction ◽  
Reduction Potential ◽  
Noise Suppression ◽  
The United States ◽  
Optimal Combination ◽  
Control Technology ◽  
Noise Levels ◽  
Turbofan Engines ◽  
Business Jet ◽  
Bypass Ratio

The business jet fleet registered in the United States as of July 1975 consisted of approximately 1500 aircraft, of which only 10 percent were powered by new, medium bypass ratio turbofan engines, and 75 percent by turbojet engines. A review of the noise reduction potential for existing aircraft has been completed on a model-by-model basis. An optimal combination of flight operational procedures and noise suppression techniques for existing engines has been derived for each aircraft model to minimize noise levels at FAR 36 certification measurement locations, consistent with existing noise control technology and operating economics. The alternative of new engine installations has also been evaluated. Comparisons between noise levels for modified and unmodified aircraft are presented.

A Drill Rod Coulomb Friction Damper

2012 ◽  
Author(s):  
Henry A. Scarton ◽  
Anne R. Guthrie ◽  
Kyle R. Wilt
Keyword(s):  
Noise Reduction ◽  
Decay Time ◽  
Coulomb Friction ◽  
Reduction Potential ◽  
Friction Damper ◽  
Peak Acceleration ◽  
Transverse Bending ◽  
Modes Of Vibration ◽  
Reverse Taper ◽  
Bending Modes

A Coulomb friction damper, consisting of a case-hardened roll-threaded collar resting against a reverse taper segment of drill rod, is studied for its noise-reduction potential. Axial impact causes the drill rod to be excited in many transverse bending modes of vibration, along with longitudinal and torsional resonances. Due to the inertia of the collar, simultaneous axial and rotational self-tightening motion occurs on the rolled thread. The collar consequently presses on the case-hardened tapered surface of the drill rod, inducing interfacial frictional rubbing, resulting in 5–45 dB of attenuation in peak acceleration of the modes of vibration, and reduction in decay time on the order of 10 seconds.

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