Muting a grand

[Sarah Fox]

> plus big caster cups set on foam

-- or on carpet squares, which won't mash as flat and will be somewhat
springier

Along the same vein, place the legs at least a foot from any wall.  I had a
Rhodes Stage 88 electric piano in college for its portability.  I was
actually a kind neighbor and did all my practicing through headsets.  One
day I received a knock on the door from the frazzled downstairs neighbor who
couldn't take my practicing any more.  It turns out the rear legs of the
piano were sitting close enough to the wall that the minute vibrations were
beautifully coupled into the lower wall, which served as a sounding board.
After six inches of movement away from the wall, he couldn't hear me at all.

There are also muting blankets, but I think they're only good for 6 dB or
so.

Contrary to popular understanding, here are the generally accepted rules of
thumb regarding materials:

To decouple vibrations from between solid objects, insert something
mushy/squishy/springy -- like foam.

However, to block airborne vibrations, don't use foam.  Air passes right
through it.  Use dense materials with lots of weight to them.  Heavy felt
(REALLY heavy) is ideal.  Think in terms of that stuff they use under the
carpets of cars.  Heavy carpet is perhaps a more cosmetic solution.

To keep a solid surface (e.g. a wall) from vibrating in response to airborne
sound, add mass to reduce its compliance.

To absorb sound instead of reflecting it back into the room, use a gradation
of materials, starting from light open-cell foam, to denser open-cell foam,
to heavy, thick felt, to a heavy, solid substrate such as 3/4" or 1"
particle board.  Foam wedges are effective too, but not as much as people
think.

If the client is, say, a concert pianist who practices 8 hr a day, he or she
might consider a sound attenuating chamber (called an "anechoic chamber," a
misnomer) from Industrial Acoustics.  Really nice stuff, but kinda pricey.
The chamber breaks apart into panels for shipment and assembly.  Even
someone in the same room as the chamber will only hear a faint tinkling.
The chamber is also an ideal "dead room" for recording and would probably
serve as a bioisolation shelter in the event of a terrorist attack! <grin>
If floor vibrations are a problem, the chamber can be set down on 1" wood
spacers -- enough to slip small innertubes underneath the corners.  Inflate
the innertubes to just enough lift the booth off of the spacers and provide
a spring action.  (The spacers are important to allow intertubes to be
replaced without disassembling the booth.

Hope that helps.

Peace,
Sarah