Methods and apparatus for electronically detecting siren sounds for controlling traffic control lights for signalling the right of way to emergency vehicles at intersections or to warn motor vehicle operators of an approaching emergency vehicle

摘要

A siren sensor for detecting siren sounds emitted from emergency vehicles and electronic processing circuits for detecting and identifying the siren sounds electronically to control the traffic signal lights at an intersection to permit only the emergency vehicle to travel through an intersection with the right of way. The method and apparatus utilizes an acoustic horn in combination with a microphone for receiving the siren sounds and converting them to corresponding electrical signals. A conventional horn is modified to function as an acoustic lens to filter and amplify the siren sounds applied to the microphone. The modified acoustic horn and microphone combination comprise a tuned and directional audio sensor sensitive in the frequency range of an emergency vehicle siren. The electronic signal processing circuitry amplifies the resulting microphone signals to obtain the maximum sensitivity to the frequency spectrum of siren sounds. Detectors tuned to a harmonic of the siren signals is utilized for eliminating extraneous sounds along with unique filtering to band pass only sounds in siren frequency spectrum to a phase locked loop detector. The validity of the detected signal is verified by tracking a portion of the siren signal in pre-selected increment under time constraints to lock up and unlock the detector to verify a valid siren sound signal has been detected and provides a valid output signal for use in controlling a conventional traffic light sequencing control or to warn a motorist of an approaching emergency vehicle.