So since the board seems to be obsessed with exhausts the last few days, i figured i may as well ask. What is the actual cause of resonance? Why does it seem so pronounced on these cars?

-Steve

 

Inquiring minds want to know.

 

Resonance is caused by the relationship of the exhaust pipes/muffler chamber size to a specific frequencie(s) produced by the exhaust/engine sound system.

 

so why the TT? What is it about this car that makes it such an issue.

If there is no muffler will there be resonance? For example, the fabspeed bypass pipes...are they just really loud with no resonance or do they resonate also?

-Steve

 

It's not just the Turbo. Check out some of the other car and truck Forums.

Sure, there can be resonance as long as there is something for the frequency to "bounce" off of. There can also be sympathetic resonance produced by sound waves causing vibration of either material not located near the sound producer or by vibration caused in any adjacent chamber(s).

 

It takes a lot of engineering and development work to tune out the resonant frequencies. With a front engine car you have a much longer exhaust system. The overall external size of the mufflers is relatively small so you have to deal with smaller chambers and fewer baffles. Also the 996 chassis/body doesn't seem to have as much sound insulation as other cars.

 

Yes it does.

But not all resonance is "bad".

 

Resonance is actually a phenomenon produced by sound frequencys vibrating within a contained area or chamber... in this case the cabin of the 911. I think that due to the fact that the cabin is shaped a certain way and that the engine with exhaust is so close to the cabin you will get drones or resonance at certain frequencies with any exhaust system you install. Even with the stock exhaust I get a bit of resonance around 2800-3200 rpm.

All cars have resonance to some degree or another. i think that we Porsche guys are just very in-tune with the sounds and fell of our cars making us hypersensitive sometimes. its all a balance between performance andcomfort.

 

Is resonance and drone the same thing? I thought that resonance was something that would cause your windows to rattle and drone is that constant low frequency humming.