My Custom Exhaust...

tchuck said:
The location of the muffler makes no difference.

The calculation is based on reducing specific frequencies. For instance, if you listen to your exhaust note and recognize a particularly loud mid range, you might record it and analyze it in terms of frequency with a visual eq. That analysis would show you that, at 4000rpm your exhaust note is twice as loud at 1500Hz as it is at 1000 or 2000Hz. Considering pressure waves always travel at the same speed (the speed of sound), you could calculate how far away from the sound source a particular division of that frequency would lie, then you would place your resonator there to reduce that frequency coupling, thus reducing the volume at that frequency.

I've literally had 7 beers tonight, so if this doesn't make sense Ill revise it tomorrow.

SfmDRuT2
Click to expand...
I learned this in Physics...
 
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tchuck said:
The location of the muffler makes no difference.

The calculation is based on reducing specific frequencies. For instance, if you listen to your exhaust note and recognize a particularly loud mid range, you might record it and analyze it in terms of frequency with a visual eq. That analysis would show you that, at 4000rpm your exhaust note is twice as loud at 1500Hz as it is at 1000 or 2000Hz. Considering pressure waves always travel at the same speed (the speed of sound), you could calculate how far away from the sound source a particular division of that frequency would lie, then you would place your resonator there to reduce that frequency coupling, thus reducing the volume at that frequency.

I've literally had 7 beers tonight, so if this doesn't make sense Ill revise it tomorrow.

SfmDRuT2
Click to expand...

I haven't had my morning coffee yet, so I'll read this over again in a bit.
Also, no matter how many beers, I'll agree with tbe sound master.
 
tchuck said:
The location of the muffler makes no difference.

The calculation is based on reducing specific frequencies. For instance, if you listen to your exhaust note and recognize a particularly loud mid range, you might record it and analyze it in terms of frequency with a visual eq. That analysis would show you that, at 4000rpm your exhaust note is twice as loud at 1500Hz as it is at 1000 or 2000Hz. Considering pressure waves always travel at the same speed (the speed of sound), you could calculate how far away from the sound source a particular division of that frequency would lie, then you would place your resonator there to reduce that frequency coupling, thus reducing the volume at that frequency.

I've literally had 7 beers tonight, so if this doesn't make sense Ill revise it tomorrow.

SfmDRuT2
Click to expand...

A quick example of how you would place a resonator to achieve a reduction at a given frequency. Also, in my drunken wisdom last night I misused (overused, rather) the term "frequency". Frequency is not a distance. The wavelength of a frequency is what can be measured in length.

Anyway, say you record your exhaust note and you find that there is a large volume spike at 150Hz for whatever reason, and that is what you want to reduce. Since 1Hz = 1 cycle/sec and the speed of sound (pressure waves) in normal air is 1130ft/sec, then you can easily deduce that the wavelength at 150Hz is 7.6ft. Ergo, a resonator placed at 7.5ft intervals will affect frequencies at and very near 150Hz.

Helmholtz resonator design is separate deal entirely, but not all that difficult to grasp. Basically, the chamber of air acts as a spring and the internal volume (fluid volume, not sound) determines the level of wave reduction on the system. Our stock intakes have Helmholtz resonators for that very reason.
 
I wish there was another FX in town with some sort of exhaust could I could get an IN PERSON idea of the differences - I mean, things sound different over the web always - I am just dissapointed. I will be removing this system later this week and going back to stock - anyone interested just shoot me a PM. I don't feel like messing around with different ways to reduce sound or anything with this vehicle, I made a silly jump decision on this exhaust and I regret it, but all is well because I have my full OEM still - so I rest easy.
 
Okay guys, I will be placing a For Sale ad coming Saturday - The exhaust is coming off Friday. I will get a few different videos as well so you guys can get a better idea of the volume. If I decide to do another exhaust it will likely be Axle back only and be a low key magna-flow or similar. If I could afford the Invidia right now I would jump on that! But I would much rather go lower and get some nice wheels first.
 
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