Some component that is moving. The movement produces the noise. A great technician will know to SHELLAC any and all coils on the main circuit board to reduce that noise. As to the battery, if it is over 2 years old or holds a 15 minute or less charge that battery could be over taxing the power supply and if you leave that battery in the usual result is a dead board or wall charger. Fix (for the battery issue) is usually the new battery. If it's worth it or not is up to you.

But the point is that an old battery can damage the main board or have folk complain about laptops eating chargers. Now you know.

A workaround can be -> Leave out the battery.