As in electronics, the fourth harmonic of a frequency is the
strongest. So damping that harmonic reduces the effect of the primary
frequency. You can see in this picture how the smaller chambers are closer to
the end of the pipe and the larger chamber closer to the opposite end. The
intake noise is a very large part of the engines total noise profile. Intake
valves shutting off a fast moving air column at various RPM is the
problem.
Similar chamber sizes appear inside complex exhaust mufflers in
automobiles.
Absorbing the peak pressure waves from the Mazda and letting them
back into the stream during low pressure troughs is what
seems the lightest and least complex mufflers being tried.
Since
aircraft engines operate at just a few RPM, it seams that various
lengths of muffler, mounted at various distances from the engine should be
investigated. Or, I could be completely wrong.
Lynn E. Hanover
In a message dated 4/11/2013 11:46:50 P.M. Eastern Daylight Time,
hoursaway1@comcast.net writes:
Marty, Lynn and others
Attached is a picture of an
intake tube for a Ford pickup truck. It got me thinking about what was Ford
thinking?!?!! And from there, how could we use this. The intake air
comes in from the left. It travels past a series of deadend offshoots, of
different sizes. Then enters the throttle body after the turn at the
bottom.
In designing the mufflers for our rotaries, there are
different pitches that are troublesome. Would a design similar to this work
for our ear shattering vibs, and let the throaty V-8 sound thru?
Just
wondering
Bob
Tilley