Bonneville America Forums Forums Technical Forums Exhaust Can we measure exhaust sound?

I may have already cornered the market on dumb questions, so here's an attempt to solidify my leadership. Every month or so, the question arises about which pipes are loudest. Couldn't one of you engineering/science types design a repeatable test? I have a digital sound pressure meter from Radio Shack (don't we all) that I would be willing to put into circulation so we could even ensure a "calibrated" meter.

Post deleted by Grump

I suggested this some time ago (so you're not the only one asking dumb questions .. standardisation wouldn't be THAT hardwe just need to make it easy to do... for example have everyone do it outside, at 12'/3m directly behind the bike, 24"/60cm off the ground, and have them run the bike at idle, 2500rpm, and 4000rpm for 3 seconds each, giving noise levels for each. You could upload that data along with an audio recording of the test so people could compare the "tones" as well as the volumes. Then we'd just need to get Robert to set up someplace to store them (or I'd be happy to store it on my site). The tricky part would be everyone who needs it getting a sound level meter, but if you're happy to send yours around (a-la the hole saw) that solves that issue.

Matt

I might suggest that we measure in decibels with the meter near the area of the riders ear. I am a safety director for a construction company and we do this often on all types of equipment. There are analog meters, they have a needle, and digital meters. Both should be plenty acurate for our uses. This evening I'll do my SM with the long slash cut Speciality Spares and my America with drilled out TOR's. It should be interesting.
Sincerely, Old 52
PS Also should be done outside in a relatively open area for consistancy, a garage puts to many variables into the mix.

Last weekend Brad and I were just kicking around the idea of creating a folder for sound bytes. Each of us could easily post sound bytes with the specs on our setups to go with them. Sounds like more work for WOJO though. This site has almost everything else available. Love it!!!!

Hey Old 52, will be very interested in your results, removed the baffling from my TOR shorts also, was wondering what your results were. I run Freaks, 160 jets, think I may have lost a bit on the low end and torque, thinking of putting a small baffle in to add some back pressure, and maybe quiet it down a tad. Wondering what your experience has been. Thanks, Jim

I think I'll have some time to check mine tonight also. For the first shot, I'll try it at both ear level and as recommended by Sandmann (at 12'/3m directly behind the bike, 24"/60cm off the ground, and have them run the bike at idle, 2500rpm, and 4000rpm for 3 seconds each). The neighbors and my family will love this.

I also recently picked up a digital video camera, which I can use to record a sound clip. I spend a lot of time working on the computer, and I'm sure I can find a way to copy out the sound.

I did a quick, seat of the pants reading on my bike out on the driveway.

At rider ear level I recorded 96 db at idle (1500 rpm); 105 db at 2500 rpm; and 107 db at 4000 rpm.

At a point 12-ft. behind the end of the pipes and two feet off the ground, those numbers are 93 db at idle, 101 db at 2500 and 109 db at 4000.

I have Bub Dresser Dogs, AI removed and 125 jets (I think).

May be interesting, but only if we have something to compare the numbers to. I want to do this again if others are interested, especially the off-the-bike readings. It was tough to do alone.

Let me know if any of you would like to use my sound meter.

BTW, I would recommend against leaving the meter on the seat when setting the throttle. Apparently the vibration causes the meter to slide a bit and fall to the ground. It's just a theory, but since it happened twice I'm either on to something or just dumb.