Glass break detector and a method therefor
First Claim
1. A method of detecting breaking glass, comprising the steps of:
- a) detecting the occurrence of acoustic waves characteristic of breaking glass and providing an output signal;
b) feeding the output signal to a plurality of parallel filters;
c) converting the outputs of the plurality of parallel filters to digital format;
d) determining the peak amplitude value of the output for each of the plurality of parallel filters over a first predetermined time period;
e) determining the average value of the output for each of the plurality of parallel filters over the first predetermined time period;
f) generating a pretrip condition signal for each of the parallel filters when the respective peak amplitude values of the filters exceeds their respective average values during the first predetermined time period by an amount which is predetermined for each filter;
g) generating a trip condition signal for each of the filters when the corresponding pretrip signals are generated for each of a sequential number of the first time periods, the sequential number of first time periods being predetermined for each of the filters; and
h) generating an alarm signal indicative of breaking glass when the trip condition signals for all of the filters have been generated within a second predetermined time period.
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Accused Products
Abstract
An acoustic transducer has an output which is fed through a preamplifier to a multiple of parallel filters. Each parallel filter passes a band of signals having frequencies within a predetermined range of frequencies. Each band of signals is converted from analog to digital and input to a signal processing unit. The peak amplitude value and the average value of the output from each parallel filter is determined. The peak amplitude value and average amplitude value are compared to determine if a pretrip condition occurs. If a pretrip condition occurs, the average value is saved and compared with the peak amplitude value for a select number of time periods to determine if a trip condition exists. A special test can be used which alters the number of time periods used in determining if a trip condition exists, based on a comparison the peak amplitude value between two of the bands. An alarm condition is generated when trip conditions occur for each of the bands of signals within a second predetermined time period.
41 Citations
27 Claims
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1. A method of detecting breaking glass, comprising the steps of:
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a) detecting the occurrence of acoustic waves characteristic of breaking glass and providing an output signal; b) feeding the output signal to a plurality of parallel filters; c) converting the outputs of the plurality of parallel filters to digital format; d) determining the peak amplitude value of the output for each of the plurality of parallel filters over a first predetermined time period; e) determining the average value of the output for each of the plurality of parallel filters over the first predetermined time period; f) generating a pretrip condition signal for each of the parallel filters when the respective peak amplitude values of the filters exceeds their respective average values during the first predetermined time period by an amount which is predetermined for each filter; g) generating a trip condition signal for each of the filters when the corresponding pretrip signals are generated for each of a sequential number of the first time periods, the sequential number of first time periods being predetermined for each of the filters; and h) generating an alarm signal indicative of breaking glass when the trip condition signals for all of the filters have been generated within a second predetermined time period. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. Apparatus for detecting breaking glass, comprising:
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transducer means for detecting airborne-transmitted sounds and providing an output analog signal; filter means responsive to the output analog signal and operative to output multiple bands of signals, each band of signals of the multiple bands of signals having frequencies within a predetermined range of frequencies; converter means responsive to each band of signals to convert each band of signals from analog to digital; signal processing means responsive to each band of signals received from the converter means and operative to determine the peak amplitude value of each band of signals over a first predetermined time period, to determine the average value of each band of signals over the first predetermined time period, to compare the peak amplitude value of each band of signals to the average value of the respective each band of signals over the first predetermined time period, generating a pretrip condition for each band of signals when the peak amplitude value is greater than the average value by a predetermined amount for each band of signals, generating a trip condition signal for each band of signals when the pretrip signal is generated for each of a sequential number of the first time periods, which is predetermined for each filter, and generating an alarm signal indicative of breaking glass when the trip condition for each band of signals has been generated within a second predetermined time period. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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Specification