The notification sound keeps going off whenever I visit the site but when I check, all the notifications are ones I've already checked.  

Do you have any topics open when the notification sounds goes off? When someone replies to a topic that you have open it will play the notification sound and provide the ability to refresh the topic, it is possible that this is the sound you are hearing.

27 minutes ago, Ben said:

Do you have any topics open when the notification sounds goes off? When someone replies to a topic that you have open it will play the notification sound and provide the ability to refresh the topic, it is possible that this is the sound you are hearing.

This was the first topic I opened in over a month. I checked my last topic to make sure this wasn't the case, and it isn't.