sub frame bracing

so these attenuators are essentially 'elephant ears' for the exhaust, the longer the tube, the lower the Hz range it affects...nominally 33.75'' might be somehwere around 30-80Hz I'd bet, barely above the lower limit of human hearing
 
Right.

[(target rpm for noise cancellation) x 4] / 60 = frequency

(speed of sound in the exhausted air) / frequency = wavelength

wavelength / 4 = length of quarter-wave


So for a 1500 rpm drone:

(1500 x 4) / 60 = 100 Hz

1125 fps / 100 Hz = 11.25 feet

11.25 feet / 4 = 2.8125 feet or 33.75 inches
 
simple! I just need space next to existing pipes for a 34" x 2.5'' tube with an elbow on it ! :)
-and..what's the rationale behind targeting the 1/4 wavelength?
 
The sound travels down the tube, hits the capped end, and travels back to the exhaust system, which effectively puts it 1/2 of a wavelength out of sync. Hence the drone/noise cancellation at the frequency it's tuned for.
 
The sound travels down the tube, hits the capped end, and travels back to the exhaust system, which effectively puts it 1/2 of a wavelength out of sync. Hence the drone/noise cancellation at the frequency it's tuned for.

ah yes, destructive interference to the drone rescue!!! and whatever rpm's (3000 or 750?) create a wavelength 2x or 1/2 that of 1500 rpm's will undergo CONSTRUCTIVE interference? that 33.75'' attenuator doubles as an amplifier?
 
The fabrication skills of many of my fellow Mark owners continue to blow me away. Imagination is not a lost talent among the users of this site. My hat is off to all of you for thinking outside of the box. Let me re-state - not just out of the box. You're thinking outside the house. You guys have the pride to not only accomplish the task, you make it look good, too. I gave the Piston Slap guy sh*t for spending too much time here - now, I get it. Every time I log on, you give me a different solution or design idea. My wife says she thinks this will end up a never-ending project. She's probably right. Just as soon as I decide - yes, that's the way I want my car to look and drive - I see someone else's ideas that change my mind. You keep an old man thinking - and judging from some of my PM's, I am not the only guy of advancing years who appreciates seeing this avocation being driven by new blood. Thank you
 

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