Electrical audio signal processing systems and devices – Monitoring of sound
Patent
1987-03-25
1988-07-19
Isen, Forester W.
Electrical audio signal processing systems and devices
Monitoring of sound
340902, 324 77E, 324 78D, 324 78F, H04R 2900
Patent
active
047590696
ABSTRACT:
A siren detection system is particularly suited for installation in an automobile for providing a warning to the driver when an emergency vehicle is in the vicinity of the automobile. The system includes a microphone mounted on the automobile. The output of the microphone is supplied to a bank of band-pass filters, each tuned to a different adjacent portion of the frequency range through which the frequency of a siren varies. The outputs of the filters are sampled by an averaging and selection circuit which produces a single output corresponding to the central one of any of the filters producing an output during a preestablished time interval. This output then is compared with the previous output (which indicates the previously selected band-pass frequency) to operate an up/down counter. Whenever successive counts of a preestablished number in the same direction occur, the output of the counter enables an alarm to indicate the presence of a siren operated by an emergency vehicle in the vicinity of the automobile. This system inherently rejects noise in the same frequency range, since random noise signals do not produce the necessary successive output counts from the counter to activate the alarm.
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Bernstein Bernard
Sohie Guy L.
Isen Forester W.
Ptak LaValle D.
SY/Lert System
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