My mitsubishi colt makes a high pitch whine from the stereo when I put the key in and start the electrics. Any?

my mitsubishi colt makes a high pitch whine from the stereo when I put the key in and start the electrics. Any idea what this could be, and how worrying it is?|||you just need a supressor put in somewhere not expensive just a few pounds its nothing to worry about just interference|||The alternator needs a suppressor installed on it.