Abstract: The present invention, generally speaking, provides an acoustic railway crossing detector. The present invention provides a means of not only detecting the presence of a train, but it can determine speed and direction of travel. This allows a more adaptive control of the railway crossing gates and may reduce the nuisance factor of having the gate close too far in advance of the train reaching the crossing. It is also much less susceptible to false activation by natural causes or acts of vandalism. In accordance with one embodiment of the invention, an acoustic railway crossing detector includes at least one acoustic emitter; at least one acoustic detector; multiple reflectors arranged to reflect acoustic energy produced by an acoustic emitter toward an acoustic detector, and control circuitry coupled to an acoustic detector for producing an indication of whether or not a train is present.

Abstract: A improved siren detector for detecting siren sounds which precess at known warble rates, such as yelp, wail, and high-low, within a selected frequency band. A transducer detects the siren sounds and produces a corresponding electrical output signal. This electrical output signal is filtered to reject signals outside of the selected siren frequency band. The signal is processed to determine the amplitude of the electrical signal, and hence the sound level of the siren sound at the transducer input. This signal is also processed by an amplitude limiter and frequency discriminator to determine the instantaneous frequency of the siren sound. This discriminator is followed by a non-linear filter to remove the FM clicks characteristic of siren sounds having a low signal to noise ratio. Selection filters are used to analyze the precession rates, maximum frequency, minimum frequency, and shape of the precession characteristic to classify the siren as to its type, such as yelp, wail, and high-low.