A signal processing system and associated methods are disclosed for reliably detecting audible alert signals, such as Temporal-3 (or Code-3) and Temporal-4 (or Code-4) alert signals generated by commercially available smoke, fire, and carbon monoxide detectors. The system and methods are capable of detecting audible alert signals of different intensities in the presence of dynamic background environment (e.g., television programming, music, noise, and the like). The system and methods are capable of detecting audible alert signals generated by far away smoke, fire, and carbon monoxide detectors. The signal processing system and methods may, in some embodiments, be incorporated into a bedside or other unit that generates a supplemental alert signal capable of alerting individuals who might not otherwise respond to the alarm condition, such as individuals who are asleep, children, hearing impaired, or intoxicated.