Glass break sensor
First Claim
1. A glass break detector for detecting the breaking of glass comprising an acoustic transducer which produces a wide band electrical signal in response to receipt of sound energy of a glass break event, and a processing arrangement for analyzing the electrical signal of the acoustic transducer for possible detection of glass break events, said processing arrangement including means for detecting a sudden increase in strength of the signal indicative of a possible glass break event and producing an activation signal, an arrangement for dividing said electrical signal into a low frequency component and a high frequency component, a sampling arrangement for each of said high frequency component and said low frequency component activated by said activation signal, each sampling arrangement dividing the respective component into a plurality of sample periods, an arrangement for collectively analyzing the sample periods of each component and determining whether the respective component is considered random, a signal shape detecting arrangement which analyses said electrical signal for an envelope shape consistent with a glass break event, and an alarm signal generator which produces an alarm signal when the analysis of said electrical signal indicates each component is considered random and said envelope is consistent with a glass break event.
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Accused Products
Abstract
The glass break detector uses sampling techniques to a low band and a high band portion of a signal from a transient event to assess whether the bands are random. In addition, an assessment of the envelope shape of the signal is made to confirm the signal is consistent with a rapid rise followed by a sloped decay typical of transient events. It has been found that dividing of the signal into high and low bands and analyzing each portion over a short front end portion of a transient event is effective in distinguishing glass break events from other common events.
34 Citations
15 Claims
- 1. A glass break detector for detecting the breaking of glass comprising an acoustic transducer which produces a wide band electrical signal in response to receipt of sound energy of a glass break event, and a processing arrangement for analyzing the electrical signal of the acoustic transducer for possible detection of glass break events, said processing arrangement including means for detecting a sudden increase in strength of the signal indicative of a possible glass break event and producing an activation signal, an arrangement for dividing said electrical signal into a low frequency component and a high frequency component, a sampling arrangement for each of said high frequency component and said low frequency component activated by said activation signal, each sampling arrangement dividing the respective component into a plurality of sample periods, an arrangement for collectively analyzing the sample periods of each component and determining whether the respective component is considered random, a signal shape detecting arrangement which analyses said electrical signal for an envelope shape consistent with a glass break event, and an alarm signal generator which produces an alarm signal when the analysis of said electrical signal indicates each component is considered random and said envelope is consistent with a glass break event.
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12. A method of detecting the breaking of glass comprising using a microphone to detect sound in an area to be monitored and produce a signal, filtering said signal to produce a low frequency component and a high frequency component, using analog to digital converters to convert both the high frequency and low frequency components to a high frequency component series of bits and a low frequency series of bits, analysing said signal to identify a sudden change in the signal indicative of a transient event,
upon recognition of a transient event analysing said series of bits of both the high frequency component and the low frequency component over a predetermined time period using sampling techniques to determine distribution of changes in amplitude of each component and whether the distribution indicates random changes in amplitude,processing said signal to determine the envelope thereof over at least part of said predetermined period and determining whether the signal is representative of a glass break signal, andproducing an alarm when both the high and low components indicate random changes in amplitude, and the determined envelope is representative of a glass break signal.
Specification