Re: [Phys-l] Vibration Isolation Specifications

[Brian Whatcott <betwys1@sbcglobal.net>]

David Craig wrote:
> All-
> ...
> The architect wants some numbers (tolerances) for vibration isolation  
> in those rooms.   These labs will be in the basement on the slab, but  
> will be on the same floor not too distant from the building's machine  
> rooms.   While very sensitive experiments will of course require their  
> own vibration isolation, I don't want the optics lab (for example)  
> vibrating away every time the fans fire up.  Ideally, I'd like those  
> labs on a separate slab.  (I don't know the underlying geology yet.)
>
> Anyone have reasonable baseline numbers for vibration limits over a  
> reasonable range of frequencies for such labs?  Or know of a source  
> for such limits?
>
> Thanks,
> David Craig
>
>
> <http://web.lemoyne.edu/~craigda/>
The physics labs with the most demanding requirements for vibration 
isolation
are the gravity wave experimentalists.
It seems sensible to read what they have to say.
Here is a note on one such effort. They know what vibration they would 
like,
and they (seem to) know what level of vibration to expect in suburban 
and quiet
ambient environments..
http://www.ligo.caltech.edu/docs/P/P020028-00.pdf
    (transcribed by hand...)

Fig 1.2 has a curve for vibration amplitudes in these situations.
I note that despite the "Physicsy" unit of measure: meters per root Hertz
which I suppose is intended to generalize the measure across frequency,
the urban environment is shown as 10^-8 at 10Hz to 10^-10 at 100 Hz.
This figure shows a quiet site as 10^-11 at 10Hz to 10^-20 at 100Hz.
Their objective is to provide a Michelson interferometer with Fabry Perot
resonant sections (or  some such) at vibration levels many orders lower.

David's mention of the likely pollution source suggests rotating and
reciprocating euqipment in the 60Hz, 30Hz, 20Hz and 15 Hz regions.
Reciprocating compressors, like your four cylinder car engine, are
prime contributors.

Coming down to Earth with a bang; an industrial supplier mentions
allowables in the larger fractions of a millimeter, I notice.
<http://www.mason-ind.com/masonind/downloads/spec/complete/VCS10082.pdf>
Transcribed by hand AND long!

Brian W