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MMD > Archives > July 2010 > 2010.07.06 > 04Prev  Next

Reducing Turbine Suction Pump Noise
By Spencer Chase

Motor Player Company made a turbine pump that was fitted to some
Welte Licensee players.  The design is a model for a quiet turbine pump
-- when mine is running you can hear just the slightest motor noise.

Noise from a turbine comes from two sources: motor noise and noise
in the exhaust.  Surrounding the turbine with noise absorbing material
will only block this source and you will still hear a horrible whine in
the exhaust.

Blocking noise is accomplished by converting the mechanical energy of
the sound wave to something less annoying, such as heat or just a wave
of a lower and less annoying frequency.  Heavy material such as lead
will certainly do it, so will a layer of very soft aluminum.  The best
results are had if the heavy material is free to vibrate but not
conduct its vibration to the outside.

Layering a heavy material with a resilient one is the best solution.
This is how most sound dampening materials are made, with layers
alternating in density.  Some such as "Ear" foam, include the dense
material within the low density material.  This is something referred
to as a "loaded" foam using something like clay suspended in a foam

The Acoustiblock material looks like a good choice for blocking the
vibration noise.  Their stud insulator looks great too.

Quieting the exhaust requires a muffler.  The air must pass over
baffles which absorb (and convert to heat) the sound energy or convert
it to a lower frequency.  The Motor Player turbine did this by passing
the exhaust over a heavy aluminum block that was suspended in felt.

I have made mufflers by cutting a number of discs that fit inside a
large tube, lined with felt and or lead sheet.  Insert discs each with
a single hole (or portion of the disc cut off at the circumference) so
that the holes in adjacent discs do not line up, forcing the air to
hit as much sound deadening material as possible.

If you have room for it, you could use a large pipe to enclose both the
turbine and the muffler.  PVC pipe is made in sizes as large 12"
diameter but don't ask me what to do with the rest of the 20-foot
length.  :)

It also helps to start out with a quality turbine that makes less noise
that has to be reduced.  Unfortunately, anything made today that is of
really good quality would be very expensive.

A good source for decent turbines is the pumps made for process
cameras and vacuum frames used in graphics.  Every print shop used to
have a process camera but computers have taken over so these show up
in junk and surplus shops everywhere.  I have two very nice turbines
mounted in foam lined boxes that would require just a little more work
to make them very quiet.

Usually you can slow down the pump considerably and still have enough
suction for a player, however you need to make sure that you allow
enough cooling air to pass through the pump as this is how the motor
is cooled.

Best regards,
Spencer Chase
Garberville, Calif. 

(Message sent Tue 6 Jul 2010, 17:07:21 GMT, from time zone GMT-0700.)

Key Words in Subject:  Noise, Pump, Reducing, Suction, Turbine

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