My camera records videos but no sound why?

I read the manual its a Nikon model #S6500 it works fine but when i playback my movies i shoot its in slow motion and no sound and so if you have this type of camera or have any suggestions i'd like that

The obvious possibility is that you're recording in slow motion. Failing that, how are you playing back the video - in the camera or are you transferring it to a PC?

Download and install VLC player from www.videoLAN.org - it is more robust and can deal with more video types than Wnidows Media Player or QuickTime. Too bad you did not tell us which computer, operating system or media player you are using.