Air vibration: TA22 (not sure it can be answered)

[Invid]

So this is a bit of an obscure question and a bit hard to describe. I'm not sure it can be solved via the internet but I'd be keen to hear peoples thoughts.

At about 2,500rpm there is a vibration of the air in the car above and beyond the exhast note. It seems to only occure between 2,500 and 3,000 rpm. I think it might be one of two things; vibration caused by the exhaust pipe or vibration from the engine/driveshaft.

My questions are:
Has anyone else had a similar problem and what was the solution?
How would you diagnose the problem?

Any help would be gratefully received

I.

[jondee86]

Could possibly be resonance ? Like the low frequency pressure vibrations inside some cars when you drive with the windows open. Kind of like blowing across the top of an empty bottle and producing a low frequency note.

Cheers... jondee86

[frr33q]

Does the vibration happen between the noted rpm in every gear selected? if yes you can discount the tailshaft/driveshaft because it rotates in relation to wheels speed and not to engine revolutions.

two things that correlate to engine speed (rpm), 1. an imbalance in the engine which could be transferring into drivetrain and then into chassis and reverberating in the cabin, or 2. exhaust is causing a reverberating sound in the cabin at these particular rpm.