An ALARM goes off every day at 2 a.m. - don't know why, please help

Over a month ago an alarm started going off everyday at 2 a.m.. I have exhausted dif. avenues to try to determine why. The alarm sounds similar to an alarm clock, but starts out slow and then reaches a frantic crescendo...and I almost swear its length of time is increasing. The alarm lasts around a minute. I used the app. to check the system and it found no errors. During the alarm, I can perform any function, so it's not affecting usage, but am desperate to find out its cause "and" cure, plus I'm tired of it making me up in the middle of night. Thanks for any help.