Abstract: An alarm system that includes a number of alarm detecting devices wherein each alarm detecting device includes an alarm condition detecting circuit, a secondary alarm activation circuit, and an audible alarm output circuit including an audio oscillator and a speaker; the audible alarm output circuit being responsive to a detecting circuit control output generated by the alarm condition detecting circuit and to a secondary triggering output signal generated by the secondary alarm activation circuit; the secondary alarm activation circuit including a microphone having a microphone output signal, an amplifier circuit in connection with the microphone output signal and generating an amplified output signal, a filter circuit having a filter input in connection with the amplifier output signal generating a filtered output signal in a first predetermined frequency range; a filter signal integrator having an integrator input in connection with the filtered output signal for integrating the filtered signal output and