The Dynavoice turbine is indeed a two-stage fan turbine identical
to what you would find in a good tank vacuum cleaner.  The racket at
24 inches of vacuum, which is soft playing, is not terrible; even at
higher levels the piano tends to compete with the turbine noise fairly
well.  However, now that I have my unit hooked up to the vacuum cleaner
in the next room, it's wonderful to have eliminated the internal
turbine noise.  The vacuum cleaner only has to run at about half speed
to generate a good solid medium volume at the piano.

As far as I can tell, all the racket from the internal turbine is from
it's vibrations being transmitted through the motor housing and through
the Dynavoice shell.  The baffle system on the exhaust seems to
actually work, and very little, if any, noise comes from the exhaust.

Mike Knudsen's statement that a Duo-Art or Ampico four-bellows vacuum
pump can easily generate the vacuum required for the Dynavoice, and
that it shouldn't be noisy, has me all excited again about tracking
down a junker I can rebuild or have rebuilt for a side-man.  When
I read that regular players only require around 4 inches of vacuum,
I figured that the bellows pump was out, but if one can indeed manage
up to 48 inches vacuum, I'm back in the market!  Any ideas where I
could lay my hands on such an item?

One other question:  Why in the world would a piano that only requires
4 inches of vacuum for normal play have such a huge over-built bellows
pump that could supply ten times the required vacuum?  Mike is right
about one other thing: the Dynavoice vacuum chamber is quite small,
and even with many notes playing there is not that much movement of air
through the system.

Tom Lear
San Francisco CA

 [ Reproducing pianos play softly at 4 to 5 inches suction, and
 [ very loud at 40 to 70 inches suction.  The 10-to-1 or more
 [ suction range is responsible for lots of valve problems unique
 [ to reproducing pianos.
 [
 [ Try measuring the sound intensity (decibels) of a chord played
 [ a different suction levels.  The reproducing piano gives more
 [ than 10 db difference.  See what range you can get with the
 [ Dynavoice.  -- Robbie