Electrical audio signal processing systems and devices – Monitoring of sound
Patent
1987-07-31
1988-11-15
Isen, Forester
Electrical audio signal processing systems and devices
Monitoring of sound
340902, 324 77E, 324 78D, 324 78F, H04R 2900
Patent
active
047854740
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 output 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. The system also includes circuits for enhancing noise rejection in the same frequency range.
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Bernstein Bernard
Sohie Guy L.
Isen Forester
Ptak LaValle D.
Sy/Lert Systems Limited Partnership
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