HELP! 8 year old daughter!!

Hello, wonder if anyone has any answers or advice please... ive caught my 8 year old daughter touching herself (while in bed) and this is simply because she keeps making a sound when shes doing it. Im unsure on what to say? I have a younger daughter and they share the same room, and its getting me really down on.how everyone in the house will hear her.. or what my little girl will grow up to think if it keeps happening? I dont want to scare her, because i understand it is her body, but i just dont think she should be doing.it so blatant around people.. and making ao much noise? Also unsure on where shes learnt it from or what shes watching. Never noticed her to watch anything unusal or in her history? Is touching yourself at 8 normal? Making noises? HELP