I've always listened to the radio when I sleep, but I don't watch too much TV (less than an hour a week). Still, radio has given positive effects to my dreams. When the morning show DJs come on in the morning I realize it in my dreams and am able to wake up on time/go lucid if I can sleep in that day. I can also faintly hear the music in the background of my dreams, which rocks, and I also experience an increase in vividness and lucidity when a song I like comes on. So, I'd say that it couldn't be too bad.
-Just to note, I also can hear those high-frequency noises from TVs, but they're quite annoying for me, so I prefer to keep to lower-power appliances in my room (I still have a dial-phone because key pad and cordless phones kept me up at night. I also had to get rid of my TV and computer...) Anyway, I've noticed that not everybody can hear it, or at least they don't notice any more. So, I'd say that it might not be that your hearing is capable of hearing higher frequencies, but that everybody else is used to hearing the noise and you are simply more perceptive. Either way, it's good to know that there's some other people who hear that kind of stuff!