When the battery in a smoke detector needs to be replaced, it is designed to create a chirping noise. Some faults are retained in the processor of newer smoke alarms.
The smoke alarm must clear any failures; however, it may signal even after the batteries are changed. This is most common in smoke alarms powered by electricity and battery backup.
When this happens, the only method to stop the chirping noise is to manually clear the fault from the processor by resetting the smoke alarm.