Finn Lassen wrote:

Here's my attempt on a simple muffler.

2" tubing, 7.75" long, 40 1/4" holes and end fishtailed to 1/4" (x 3"),
2.7 sq inch slightly less area than the 2.9 sq inch of the 2" tubing,
but more than the 2.2 sq inch area of the 1.75 header tubes. All tubes
are .035 walls.

  SNIP

Is there any way to send a sound? Maybe a .waw file?

Finn

Probably but I don't have the capability to test it. A Radio Shack
DB meter held at some standard distance from the plane would be a better

way

of quantifying noise.

Paul Lamar

Finn,
    Since my muffler is very similar, 2" tubing 15" long with 5/16" holes
and fishtailed to 1/2", I am highly interested in any results.  I was
looking at Sound Meters on the Web, but most are rather expensive for a one
time use, however, I'll take Paul's suggestion and look into what Radio
Shack has to offer.

Ed Anderson

I'll bring my Radio Shack DB meter to Tracy's flyin as it sounds like (pardon the pun)
 both of you guys will be there. Also Finn I can meet you about the 8th or 9th of Dec
as I will be landing in Tampa via UAL. for a North Fl visit with Tracy and Art Luther.

Paul Lamar

Finn Lassen wrote:

No marked improvement on the ground (idle to 3000 RPM). Maybe a bit better in the cockpit
while flying. I need to run with and without several times.

I tried enclosing it in a 3' long 3" tube (on the ground). Didn't seem to lessen the
volume, just changed it to a much lower note.

No whistle sound.

Paul is right that I should make the comparison with a sound level meter (curve A to
parallel the human ear) to get exact results. Actually a spectrum analyzer would be even
better. Suppose I get hold of a recorder that records true level without compressing it,
does anybody here know of a shareware program to take the sound from the sound card input
and display it on the screen as a frequency spectrum?

I taped the sound with my camcorder but couldn't hear any difference. Probably not a valid
test due to the level compression in the sound recording part of the camcorder.

I didn't know Tracy is holding a flyin in December. Flying up to see him this weekend and
do a prop swap.

Looking forward to see you here in December Paul and Ed.

Finn

Nope. Hopefully Tracy will do his fly in real near Sun & Fun in April so I can make
only one trip out from the west coast then :-). Hopefully Ed will be ready
to fly down from N.C. in April.  My Dec trip is part of our family 
vacation. I will meet Robin and more of the family in St Thomas on 
the tenth or 11th.

Paul Lamar


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