The answer to 'smoke detector making buzzing noise' is that a buzzing or chirping smoke detector is usually caused by a low battery or a malfunction. This can indicate that the smoke detector needs to be replaced or repaired.
Smoke detectors will often make a loud, intermittent buzzing noise when the battery is running low, as a warning to homeowners to replace the battery. If the battery is not replaced, the smoke detector may stop working altogether. Another common cause of a buzzing smoke detector is a malfunction in the internal components, which can happen over time as the detector ages.