Hi Bettie.
I think what you can do is open two browser windows. Connect to the GT site in both of them. In one of those windows enter the group and put your sound on. You can then switch back to the other window to browse the forum or indeed visit other sites. When anyone enters the group the bell will alert you and you can switch back to that window. Hope this helps.
Of course all the groups other than the Open Groups do have a moderator so if you can ever make one of those there will always be someone there for you to talk to.