Resources:
Georgia Tech Professor Ken Cunefare: ken.cunefare@me.gatech.edu
project 3B.1

A new approach to squelching noise in hydraulic systems applies compliant linings to noise-control devices for fluid-power systems.

A research team from Georgia Tech, with funding from the Engineering Research Center for Compact and Efficient Fluid Power (CCEFP), seeks to reduce noise and vibration by putting engineered-compliant materials into existing components. The materials may also reduce the size of noise-control devices.

Noise is an all too familiar problem in the fluid-power industry. Fluid-borne noise generated by components within hydraulic systems, most significantly pumps, can couple to structures and cause vibration and air-borne noise. Excessive noise increases mechanical fatigue and reduces component life, not to mention posing a health hazard to nearby workers.
Current methods for reducing fluid-borne noise rely on pressurized, gas-filled bladders that add compliance to fluid-power systems. Engineers also include design features that address noise sources such as cavitation and structural vibrations.

Pressurized bladders used in commercially available in-line silencers and in accumulators act as low-pass filters. But the high speed of sound in hydraulic fluid, along with the low fundamental frequencies of pumps, results in wavelengths of fluid-borne noise that are much longer than the practical size of common noise-control components.

To eliminate these difficulties, the research team added a polymer lining — made of a nonhomogeneous, microvoided engineered material — to a prototype silencer. Experiments showed that the silencer produced 25 dB of transmission loss from 200 to 3,000 Hz, and performed comparably to a similarly sized commercial bladder-style silencer. The team has also built other noise-control devices that incorporate the lining, including a Helmholtz resonator, tuning coil, and a Quincke tube.

The prototype Helmholtz resonator is reportedly two orders of magnitude smaller than an unlined resonator of the same resonant frequency.

The team’s test rig permits research into the acoustic performance and transmission loss of two-port hydraulic components including silencers, accumulators, hoses, branch resonators, and valves.

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