I've noticed a strange tone emanating from underneath my 2005 A4 3.0, audible from within the car. It's evident at idle and while in motion.

I thought it was the brakes, but I got them replaced, and the tone is still present.

It sounds like the noise made from blowing into the opening of an empty glass soda bottle.

The weird thing is, it's not ALL the time... it's only MOST of the time... It seems to dissipate for a while after I go to the car wash.

I know very little about cars, so can someone please offer up some possible causes for this?

Thank you in advance.

 

Exhaust. The car wash cools the metal and it contracts.

Check your oil, I had a truck that made a noise like that when the oil was low. But not all the time.

I hope it's not your catalytic converter. Have you had any power loss?

Get out the garden hose and spray the exhaust until you hit the part that makes it stop.

 

Thanks for the reply...

The car has dual exhaust... so would that mean it could be coming from just one side? Also, I have not had any power loss, and the check-engine light hasn't come on...

I just looked this up online... What's the difference between an exhaust manifold and an exhaust manifold gasket?