Jet Noise Reduction through Liquid‐Base Foam Injection

Fluidic Chevrons for Jet Noise Reduction

Chevron mixing devices are used to reduce noise from commercial separate-flow turbofan engines. Mechanical chevron serrations at the nozzle trailing edge generate axial vorticity that enhances jet plume mixing and consequently reduces far-field noise. “Fluidic chevrons” generated with air injected near the nozzle trailing edge create a vorticity field similar to that of the mechanical chevrons ...

Vibration and Noise Reduction Optimization Design of Mine Chute with Foam Aluminum Laminated Structure

The mining chute is an important equipment in the process of coal transportation and coal screening preparation. During the working process, the mining chute will generate a lot of vibration and noise because of constantly friction and impact of gangue and coal blocks. In order to reduce the vibration and noise during the operation of the chute, a new type of foam aluminum laminated structure i...

Noise reduction through compressed sensing

We present an exemplar-based method for noise reduction using missing data imputation: A noise-corrupted word is sparsely represented in an over-complete basis of exemplar (clean) speech signals using only the uncorrupted time-frequency ele­ ments of the word. Prior to recognition the parts of the spectro­ gram dominated by noise are replaced by clean speech estimates obtained by projecting the...

Turbofan Jet Noise Reduction via Deflection of the Bypass Stream

We describe a parametric experimental study of noise reduction via de ection of the secondary stream in dual-stream jets. The jets simulated the exhaust of turbofan engines with bypass ratios 4.5 and 6.0. The secondary (bypass) stream was de ected downward by means of vanes installed inside the bypass duct. Variables included the number of vanes, vane angle of attack, azimuthal placement, and a...

The Reduction of Supersonic Jet Noise Using Pulsed