Standard tone
Most smoke and CO alarms give off a beeping noise that is piercing and persistent enough to alert homeowners to danger.
Voice
Many preteenagers slept through tone alarms but awakened to the sound of their mother's prerecorded voice, according to a
2006 study in the journal Pediatrics. Several voice-command alarms are on the market, but it is not clear whether they offer
the most effective way to awaken your children in a fire. The latest revisions to the construction standard for smoke alarms
limits the verbal warning to less than 2 seconds in duration. For more information, read Smoke Alarms for Kids. [link is part of this story]
Strobe
Smoke alarms with integral strobe lights are available and are the best choice for the hearing impaired. There are also strobe
models designed to be added to some alarm models.