As Eric Bergstrom pointed out, I forgot to specifically mention brush
noise and lumped it together with "motor noise."  It is definitely true
that the high-frequency noise is more difficult to dampen.  It will
make its way through even a small airway.

The Motor Player pump has the advantage of being made of more
substantial metal than modern pumps, which are all sheet metal and
plastic.  There is less turbine noise and the turbulence is damped by
the more massive components.

If space is no problem, it should not be difficult to make a very quiet
pump.  I tried many attempts to make a pump quiet enough to fit in my
Vorsetzer, but could not get anything as quiet as the Motor Player pump
that would fit in the same space.

I rebuilt the MP pump with high-speed sealed bearings and had the
armature rewound and balanced.  It now has class N (I think) wire and
can run hot, if necessary; so less cooling air is needed.

I bought an industrial centrifugal pump that had a separate cooling
fan and thought this would work well, since I could run it nice and
slow.  It was quite expensive but had cheap plastic parts that were
crimped in place.  It lasted less than a month.

There are some very nicely made belt-drive centrifugal blowers that
could be run by a brushless motor; but they are not cheap.  With a
suitable set of timing-belt pulleys, it should be possible to run a
motor fairly slowly and the pump at a high speed.  I did this as a
test, but never used it for a piano.

The best solution really is to use a remote pump.   My Duo-Art has the
pump under the house.  I use a noisy DC motor that I can speed-control
easily.  It doesn't matter that it is noisy, since it is under the
house.

My second-most-quiet centrifugal pump was made with PVC sewer pipe
lined with felt and with baffles both in and out.  Adding some lead
would have made it better.  I still have it somewhere and could drag it
out and experiment with it.

I prefer to avoid working with sheet lead.  An alternative is very soft
aluminum.  I have some samples of self-stick dead soft aluminum that is
made specifically for dampening noise.  It is only .015" thick or so;
but it is amazing how effective it is, and it is less toxic than lead.
It is especially good for the high frequencies when they are conducted
through a solid, but it is not very effective against airborne noise.

Spencer Chase
Garberville, CA
www.spencerserolls.com