New accounts have no sound

Hi, I have a young guest coming over for a visit, so I tried setting up a guest account for her. When i tested it, I noticed that there was no sound! There was no sound in games, no sound in GarageBand. I made sure the volume was turned up. I switched back to my regular account and had sound.

So i thought that might be because it was a "Guest" account. So then I decided to set up a regular user account, and that had no sound either. Finally, I tested an alternate account that I had set up in the past and that had sound. So it seems like it has something to do with new accounts that are set up. Advice appreciated.