Long-duration signal detection in a noisy environment

A long-duration signal detector that can be used to alert a hearing-impaired person to the presence of the sound of a siren is developed. The design utilizes circuitry that allows the signal detector to discriminate between short-duration and long-duration signals. The combination of the effect of the long-duration `gating´ and the bandpass filtering process on the input signal causes the circuit to detect the presence of signals with long duration