Pendulum Outlaw 904 tips - YouTube
Crank it up!
I took some sound measurements last fall because I wanted to track the sound quality as I changed the car. Unfortunately I did not get too many data points before the weather turn. I will the post the results but it is really not quality data. Over the winter I changed the muffler, changed the seats, added a roll bar removed some of the rear padding, the exterior mirror is presently off the car. Speed was measured with a gps unit and and the sound meter is a Omega unit.
2012, 50kph - 75dB, 80kph - 78.5dB
2013, 50kph - 74.3dB, 80kph - 77.5dB
So with all the changes the car got a little bit quieter. I would say the muffler did not increase in sound level but the tone appears to me to be lower. I think the biggest contributor to the noise level is powertrain noise, I have street urethane bushings on the spring plate and old original rubber engine / trans mounting, which I will update next.