Glass break detector
AssigneeDigital Security Controls Ltd.
InventorsDennis Cecic, Hartwell Fong
Life of this patent
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Abstract
The glass break detector uses sampling techniques and statistical analysis of the acoustic signal to determine whether a random type signal typical of a glass break event has been detected. A host of experiments are analysed and the collective results investigated to minimize the effect of one time non-typical occurrences in the signal. The statistical results are preferably used in combination with other techniques for identifying glass break events.
Claims15
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, a processing arrangement for analyzing the electrical signal of the acoustic transducer for detection of glass break events, said processing arrangement including means for detecting a sudden high amplitude transient event that could be caused by the initial portion of a glass break event, waiting a short period of time after detection of a sudden high amplitude transient event and thereafter sampling the signal over a further period of time which would include the high frequency glass shattering portion of a glass break event, said signal being sampled by dividing the signal into many short segments and analyzing each short segment for an assessment of the degree of randomness in the short segment, using the assessment of the short segments to distinguish periodic signals from glass break signals and upon recognition of a glass break signal producing an alarm signal.
A glass break detector comprising
- means for detecting a sudden transient event which could be a glass break event and producing a signal derived from said transient event,
- means for sampling the signal after a specified delay to form successive experiment segments when a sudden transient event has been detected where each experiment segment comprises a series of many samples,
- means for evaluating the experiment segments using statistical techniques for characteristics which distinguish periodic signal sources from glass break event signals which are not periodic,
- and means for producing an alarm when said means for evaluating indicates the signal is not periodic.
A method of detecting the breaking of glass comprising using a microphone to detect sound in an area to be monitored, using an analog to digital converter to convert the signal from the microphone to a series of bits, analysing the series of bits over time to determine a measure of change in amplitude occurring in the signal in a first experiment, repeating the experiment many times, determining the distribution of changes in amplitude of the experiments and determining if the distribution is indicative of a glass break event by using the distribution to determine other statistical factors which assist in distinguishing a glass break event from other transient events.
Dependencies are inferred from the claim text.