Why is my Audi A4 making a humming noise?

I recently noticed that my Audi A4 is making a constant humming noise, even when the engine is turned off. What could be causing this and how can I fix it?

It is possible that the noise is coming from the tires, specifically if they are worn down or unbalanced. I recommend getting them checked and replaced if necessary. It could also be a problem with the alternator or another engine component, in which case it would be best to take it to a mechanic for further diagnosis.

Have you recently installed any aftermarket parts or accessories? In some cases, these can cause strange noises in the car. I suggest removing any recently added components and seeing if the noise persists. If it does, it may be best to have a professional take a look at your car to determine the exact cause.

Is the noise only present when the car is moving? If so, it could be an issue with the wheel bearings. This is a common problem in Audi A4s and should be addressed as soon as possible to avoid further damage. I recommend taking your car to a certified Audi mechanic for inspection and potential repair.