Bob,
Was your prop installed when these readings were taken?

Mark S.  -----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Bob White
Sent: Wednesday, January 11, 2006 6:00 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Cool Tube Muffler Sound Readings

Today I ran the engine to get the sound level readings.
  
Short review:
This is the cool tube muffler built by Jerry Hey.  Each exhaust port
has a short tube into a large round can.  The center of the can has a
two inch tube down the center to permit cool air to aid in cooling the
exhaust.  This tube is sealed from the actual exhaust gasses.  The
exhaust exits the large tube thru a rectangular tube at the bottom of
the large round can.  (photo attached)

Here are the sound level readings with the engine running at 3000 RPM

Location A C
-------------- --- ---
Left Wing 98 105
Right Wing 96 105
Front (5 paces) 95 105
Tail 91 103
Pilot Seat 84 94

The A weighting cuts out the low frequencies below 500 Hz.  I have no
idea how these compare to the typical aircraft engine.  According to
the instruction manual, the A weighting is used to determine area noise
levels, and C wighting is used to measure sound levels of musical
instruments.  I will get some higher rpm measurements after I get a little more time
on the engine.

Coolant temps seemed to stabilize at 200F and oil at 175F with the
engine at 2500-3000 rpm tied down and no cowling installed.  I ran it
for around 10 minutes in this mode.

Bob W.