In the last few days, whilst driving my car I.

In the last few days, whilst driving my car I have noticed that when accelerating to a faster speed I am hearing a humming noise from what I believe is the engine. I cannot hear this noise with the engine running and the car is stationary. I have also noticed just today a rattling noise from the right back part of the car. This is where it sounds like it could be coming from anyway. Any idea what the problems could be?