Mac os 10.6.8; Firefox 48.0.2
Today I checked email w/ both Safari and later Firefox. I went to Utube and then set up a Goggle acct so I could comment on a Utube video. I then decided I'd delete the Gmail/Google acct - I can't remember exactly why. I never confirmed the account via that link in an email to my comcast acct. I got tired and decided to check tomorrow if the account was never confirmed or added. If not, I'd follow the instructions to delete.
Later I was simply reading fanfiction at fanction.net w/ Firefox when I heard a musical dong and I still hear it intermittently. Sometimes it sounds like there are 2 or 3 notes. It now sometime sounds like some song is playing a couple of notes and stopping or I get just the dong.
I shut down the mac and rebooted and opened only firefox. The sound is still there.
I checked that no other firefox windows were open w/ some ad playing. I googled for macs w/ intermittent sounds suggestions. There was one example of a gmail icon in the browser window with something you uncheck, but I do not see any such icon. I checked my clock settings. I never use Mail and it is not open. Under login items in system preferences are realplayer downloader agent and instalutilLaunch.
I have read of hardware warning sounds but I don't think this musical note sounds like a hardware warning. I also ran the mac's hardware check recently, altho I found it lacking in that it gave me no list of what exactly it checked.
I went to sounds in system preferences and listened to the ones listed and none sounded like what I'm hearing. I don't see any way to associate the sounds w/ an activity like I could in Windows. I figure there must be a way since the sounds are there. Maybe you do it thru individual applications?
I have downloaded the free avast dmg per another post and I'm going to finally run a scan on this 7 year old Mac tomorrow am if the creek don't rise. First I'm going to make sure the Goggle acct is deleted. I am slowly preparing to upgrade to el capitan so I can upgrade Safari and Firefox, but I'm waiting for my sister to get her Windows lemon working before I do so. We are very dependent on my ability to write emails & letters at the moment.
Any suggestions how I got this sound and what to do about it?