@Mavyc it sounds loud because the drone acts like a sound box and amplifies the sound ,i would be concerned if it didnt come on ,in the very warm weather we have experienced in the UK recently if you are running the drone with the props off inside doing a firmware update for instance, then its best to have a fan blowing over it to help with cooling
if the drone is in the direct sunlight while you are waiting for the GPS to get a lock then it will make the fan run and even when you have flown in the hot weather the fan will be running as you make preparations to land ,this is quite normal get the battery out of the drone as soon as you can after switching off and dont leave the batteries in a hot vehicle the boot is normally cooler