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Vibration Isolation Technical Article- Interesting







I abstracted the following from a whitepaper (link) published by Ametek/TMC, a big vibration control equipment manufacturer. It's a good description of what you need to do to really isolate a turntable from FLOOR vibration. Floor vibration in my experience typically has a source frequency around 5 Hz, more-or-less. My little project was undertaken to reduce structure-borne vibration arising from airborne sound exciting the relatively "lively" steel furniture my TT was sitting on. I feel it got some results in that area. However, their graph, which appears to me technically correct, suggests the vibration isolation for my project is effective only in the audio range, above 40-50 Hz in fact. That seems useful, nonetheless, seeing that I don't discern any amplification of floor vibration.

Extrapolating the idea, however, lightweight platforms on relatively stiff foam pads would be effective for isolation at even higher audio frequencies, curtailing their benefit.

From TMC: "Homemade [vibration] isolation systems - often a steel or granite slab placed on rubber pads, tennis balls, or air bladders - will work only if the disturbing vibrations are high frequency and minimal isolation is required. While all isolators use the principle of placing a mass on a damped spring, their performance is differentiated primarily by spring stiffness: the stiffer the spring, the higher the resonant frequency. Thus, homemade solutions are limited by their high resonant frequency.

"A tennis ball under a steel plate [or granite slab] with a 7 Hz resonant frequency begins to isolate above 10 Hz and reduces vibrations by 90% at 30 Hz. But most building floors exhibit their highest vibrational displacements between 5 and 30 Hz, so that a tennis ball or rubber pad actually makes the problem worse by amplifying ambient frequencies between 5 and 10 Hz.

"[By contrast, a pneumatic] piston isolator with a 1.5 Hz vertical resonant frequency begins to isolate at 2 Hz and can reduce vibration by over 95% at 10 Hz." This refers to the superb gas-piston isolation tables these dudes manufacture for things like electron-microscopes.

If you want to get serious about vibration isolation, this company's platforms and similar ones come up for sale on eBay under the industrial category for pennies in the dollar, if you can own a forklift- they run a few hundred lbs!






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Topic - Vibration Isolation Technical Article- Interesting - mr.bear 23:41:21 06/19/17 (13)

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