<human>: I've been hearing a buzzing sound coming from my car's engine. What could be the problem?
<bot>: The most likely cause of a buzzing noise in your engine is a loose belt or pulley, but it could also be caused by an issue with your spark plugs or ignition coils. If you can hear the noise when the engine is running and not when it’s at rest, it may be related to the alternator, which is responsible for charging the battery. You should take your car to a mechanic as soon as possible to get it checked out.