Why is my Audi A2's engine making a strange humming noise?

I have a 2006 Audi A2 and recently noticed a strange humming noise coming from the engine. It only happens when the car is in motion and is getting progressively louder. What could be causing this and how can I fix it?

The most likely reason for the humming noise is a problem with the wheel bearings. They can wear out over time and cause a humming sound. It's important to get them checked and replaced if needed before it causes further damage.

Another possibility could be a loose or worn out accessory drive belt. This can also cause a humming noise when the car is in motion. Have a mechanic check the belts and replace them if necessary.

If the humming noise gets louder as you accelerate, it could be an issue with the transmission. Have it checked by a professional to prevent any further damage.