Siren detector

DETAILED DESCRIPTION This invention provides a siren detector capable of reliably detecting the sound of a siren while effectively discriminating against ambient street noises.
More particularly, the invention provides an audio range siren detector comprising audio pick-up means, at least two narrow pass electronic filter means responsive to the pick-up means and having closely spaced resonance points in the region of fundamental siren frequencies for producing a distictive actuating signal, timing means responsive to one of the actuating signals for generating a timing signal of short duration, gating means responsive to the filter means for producing an actuating signal upon initiation of the actuating signal from each filter means, control means responsive upon the occurrence of a pre-determined pattern comprised of all of the actuating signals within the duration of the timing interval to produce output and utilization means responsive to the output from the control means.
In the preferred practice of the invention, narrow band width filters having fast rise times and having resonant frequencies at increments of 25 cycles (for example resonant frequencies of 800 and 825) are employed in order to provide valid siren detection either for an increasing frequency mode or a decreasing frequency mode even in the presence of talking, music, horns or other street and traffic noises.