Hi Dwayne;
When making changes to your muffler it would be nice to have a decibel meter to get a measurement. These can be found on ebay for reasonable prices, however I also found a free app called DeciBell for my android phone. It seems to work great and while I don't have a lot of confidence in it's accuracy compared to a professional quality meter, it will allow you to make some meaningfull before and after measurements when making changes. Attached is a screen shot of the app. This app is in the android market and may also be available for iphone.
I realize that not everyone has a smartphone, but I know of a heck of a lot more people that have smartphones, than I know with decibel meters, so if have one or have a friend with one and can get him to install the app then it's a handy tool to make a quantitative measurement of the effect of your changes.

Todd Bartrim

On 2010-07-12 2:42 PM, "Dwayne Parkinson" <dwayneparkinson@yahoo.com> wrote:

That's very interesting.  Thanks for the info.

________________________________
From: Mark Steitle <msteitle@gmail.com>
To: Rotary motors in aircra...

Sent: Mon, July 12, 2010 10:58:42 AM
Subject: [FlyRotary] Re: Mufflers

Dwayne,
 
I added a cone-shaped 3" to 2.5" reducer to the exit of my DNA muffler to try and quiet i...