In all likelyhood it’s probably just the age of the alarms that’s causing them to malfunction, what I described is the way smoke alarms SHOULD sound when they’re operating correctly. Me & my family once lived in a house that had smoke alarms original to the house, which eventually started to malfunction & beep randomly, prompting us to replace them. After that the new ones didn’t give us any trouble. Replacing yours SHOULD fix the problem.
Once you install the new alarms, be sure to test them with smoke. I’d recommend Smoke Sabre: http://www.smokesabre.com Safer than matches, fully recyclable, won’t damage or affect the sensitivity of the detector, & easy to use.