Q: tracking chime sound!!!!

can someone help me figure out how to track down a periodic chime sound that i would like to turn off?

it is really annoying and i want to spend the time tracking this down (activity monitor or other process tracking?) since there is no convenient way in yosemite AFAIK to figure out what is making sounds that i don't want to listen to...

any suggestions? skype is not on but tracking which apps are on seems like a very inefficient and actually not likely way to troubleshoot this.

can i try and find this in notifications?!

ideas?

THANKS