Its pitch black most of the time and you wear headphones to hear the sounds. So depending on if they are scared of the dark or not. And I mean dark where you can't see your hand in front of your face.
My kids are not easily scared and enjoy almost everything at WDW, but we tried this attraction when the kids were younger and had to take the youngest 2 out. It is very dark, and you have to listen/pay attention to the script coming from the headphones to get anything out of it at all. My youngest is now 7 and we still have not tried it again, maybe next trip??
I would say no. We usually do this all the time at MGM because my husband likes it. Most of the time, the younger kids are really confused by the whole darkness thing. It is totally pitch black and the kids don't get the concept that's the attraction hasn't really broken down. I've heard lots of "Mommy/Daddy, the picture broke" comments.
We took our DD to WDW when she was 4. It's a Bug's Life spooked her but Sounds Dangerous didn't. The only problem was she didn't really understand everything that was going on. I just held her hand when it was dark and she was fine. But it does depend on how scared your 4 year old is of the dark. It's totally dark!
As long as the child isn't afraid of the dark I think they'll be fine. It's pretty much sitting the total darkness with headphones on. If the noises bother the child they can simply take the headphones off and sit in the dark If you decide to skip it, you won't really be missing much. It's a neat idea, but really I think it's not a whole lot of fun. I wish they would bring back Superstar Television instead.
Sounds Dangerous in MGM is a stage show instead of watching a show, you actually start out with a short video and lose the feed and have sound only. It takes you thru a "detective" scene with sound only. I was super excited to try it and hated it, thought it was a big waste of time.
As for a young child, I would say it would not be a good experience, between the dark and the often lsudden noises at times, I would think it would be frightening.