A security system includes a transducer within a monitored space responsive to audio signals therein. An analog-to-digital converter couples the transducer to the input of a digital signal processor. Time-staggered digital samples are stored, and are each multiplied by the current sample in a corres
A security system includes a transducer within a monitored space responsive to audio signals therein. An analog-to-digital converter couples the transducer to the input of a digital signal processor. Time-staggered digital samples are stored, and are each multiplied by the current sample in a corresponding series of multipliers, and accumulated in a like series of accumulators. Accumulated sums, generated by the series of accumulators during known, undisturbed periods, are stored. During active monitoring, the processor compares currently generated accumulated sums to the previously stored accumulated sums generated during undisturbed periods. The processor creates an alarm signal when current values for the accumulated sums do not correspond to accumulated sums previously stored during undisturbed periods.
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1. A system for detecting a disturbance within a monitored space, comprising in combination: a) a transducer disposed within the monitored space for creating an analog electrical signal in response to audio signals within the monitored space;b) an analog-to-digital converter coupled to the transduce
1. A system for detecting a disturbance within a monitored space, comprising in combination: a) a transducer disposed within the monitored space for creating an analog electrical signal in response to audio signals within the monitored space;b) an analog-to-digital converter coupled to the transducer and generating a digital signal corresponding to the analog electrical signal currently created by the transducer;c) a digital signal processor having an input coupled to the analog-to-digital converter for receiving the digital signal generated by the analog-to-digital converter, the digital signal processor providing: i) storage for storing n digital signal samples S0, S−1, S−2, S−3, . . . , S−(n-1) corresponding to digital signals received by the digital signal processor during a most recent n periodic sampling intervals, wherein n is an integer greater than 50, wherein S0 is the digital signal sample received during a current sampling interval, wherein S−1 is the digital signal sample received during an immediately preceding sampling interval, wherein S−2 is the digital signal sample received two sampling intervals before the current sampling interval, wherein S−3 is the digital signal sample received three sampling intervals before the current sampling interval, and wherein S−(n−1) is the digital signal sample received n−1 sampling intervals before the current sampling interval;ii) a plurality of multipliers, each such multiplier multiplying digital signal sample S0 by one of digital signal samples S−1, S−2, S−3, . . . , S−(n-1) to produce a corresponding product;iii) a plurality of accumulators, each accumulator being coupled to a corresponding one of the plurality of multipliers for accumulating the products produced thereby over a series of sampling intervals to generate corresponding accumulated sums;iv) storage for storing the accumulated sums generated by the plurality of accumulators, said storage including storage locations for storing in memory normal accumulated sums generated during known periods when the monitored space is not disturbed;d) the digital signal processor comparing currently generated accumulated sums to previously stored normal accumulated sums generated during known periods when the monitored space was not disturbed, and generating an alarm signal when the current values for the accumulated sums do not correspond to normal accumulated sums previously stored during at least one known period when the monitored space was not disturbed. 2. The system recited by claim 1 wherein the transducer is a microphone. 3. The system recited by claim 1 wherein the digital signal processor samples between 100 digital signals per second and 5,000 digital signals per second. 4. The system recited by claim 1 wherein the digital signal processor stores at least 100 digital signal samples S0, S−1, S−2, S−3, . . . , S−(99). 5. The system recited by claim 1 wherein each accumulator includes an adder for combining the product of the corresponding multiplier and the accumulated sum generated by the corresponding accumulator during the immediately preceding sampling interval. 6. The system recited by claim 5 wherein each adder includes an attenuator to attenuate the accumulated sum to prevent the accumulated sum from increasing infinitely. 7. The system recited by claim 1 further including a wireless transmitter for transmitting the alarm signal to a receiver. 8. The system recited by claim 1 further including: a) a second transducer disposed within the monitored space for creating a second analog electrical signal in response to audio signals within the monitored space;b) a second analog-to-digital converter coupled to the second transducer and generating a second digital signal corresponding to the analog electrical signal currently created by the second transducer;c) the digital signal processor having a second input coupled to the second analog-to-digital converter for receiving the second digital signal generated by the second analog-to-digital converter, the digital signal processor providing: i) storage for storing n second digital signal samples S20, S2−1, S2−2, S2−3, . . . , S2−(n-1) corresponding to second digital signals received by the digital signal processor during a most recent n periodic sampling intervals, wherein n is an integer greater than 50, wherein S20 is the second digital signal sample received during a current sampling interval, wherein S2−1 is the second digital signal sample received during an immediately preceding sampling interval, wherein S2−2 is the second digital signal sample received two sampling intervals before the current sampling interval, wherein S2−3 is the second digital signal sample received three sampling intervals before the current sampling interval, and wherein S2−(n-1) is the second digital signal sample received n−1 sampling intervals before the current sampling interval;ii) a second plurality of multipliers, each such second multiplier multiplying the second digital signal sample S0 by one of second digital signal samples S2−1, S2−2, S2−3, . . . , S2−(−1) to produce a corresponding second product;iii) a second plurality of accumulators, each accumulator being coupled to a corresponding one of the second plurality of multipliers for accumulating the second products produced thereby over a series of sampling intervals to generate corresponding second accumulated sums;iv) storage for storing the second accumulated sums generated by the second plurality of accumulators, the digital signal processor storing in memory the second accumulated sums generated during known periods when the monitored space is not disturbed;d) the digital signal processor comparing currently generated second accumulated sums to previously stored second accumulated sums generated during known periods when the monitored space was not disturbed, and generating an alarm signal when the current values for the second accumulated sums do not substantially correspond to second accumulated sums previously stored during at least one known period when the monitored space was not disturbed. 9. A method of detecting a disturbance within a monitored space, comprising the steps of: a) providing a transducer within the monitored space for converting audio signals into analog electrical signals;b) converting the analog electrical signals into corresponding digital signals;c) receiving a current digital signal sample S0 at periodic sampling intervals;d) storing n digital signal samples S0, S−1, S−2, S−3, . . . , S−(n-1) corresponding to the digital signals received during the most recent n periodic sampling intervals, wherein n is an integer greater than 50, wherein S0 is the digital signal sample received during a current sampling interval, wherein S−1 is the digital signal sample received one sampling interval before, wherein S−2 is the digital signal sample received two sampling intervals before, wherein S−3 is the digital signal sample received three sampling intervals before, and wherein S−(n-1) is the digital signal sample received n−1 sampling intervals before;e) multiplying digital signal sample S0 by at least one of digital signal samples S−1, S−2, S−3, . . . , S−(n-1) and accumulating the product of such multiplication in a first accumulator over a plurality of periodic sampling intervals to produce a first accumulated sum;f) multiplying digital signal sample S0 by at least another of digital signal samples S−1, S−2, S−3, . . . , S−(n-1) and accumulating the product of such multiplication in a second accumulator over a plurality of periodic sampling intervals to produce a second accumulated sum;g) storing values for the first and second accumulated sums obtained when the monitored space is not disturbed;h) comparing current values for the first and second accumulated sums to the stored values for the first and second accumulated sums; andi) creating an alarm signal when the current values for the first and second accumulated sums do not correspond to values stored in step g). 10. The method recited by claim 9 wherein the transducer is a microphone. 11. The method recited by claim 9 wherein the step of receiving a current digital signal sample S0 at periodic sampling intervals is performed at a rate of between 100 digital signals per second and 5,000 digital signals per second. 12. The method recited by claim 9 wherein the step of storing n digital signal samples includes storing at least 100 digital signal samples S0, S−1, S−2, S−3, . . . , S−(99). 13. The method recited by claim 9 wherein, within step e), the step of accumulating the product of such multiplication in a first accumulator over a plurality of periodic sampling intervals to produce a first accumulated sum includes the steps of: combining the multiplication product with the current value of the first accumulated sum in the first accumulator to generate an updated accumulated sum for the first accumulator; andstoring the updated first accumulated sum in the first accumulator. 14. The method recited by claim 13 wherein the combining step includes the step of attenuating the first accumulated sum to prevent the accumulated sum from increasing infinitely. 15. The method recited by claim 9 wherein the step of creating an alarm signal includes the step of wirelessly-transmitting the alarm signal to a receiver. 16. The method recited by claim 9 further including the further steps of: j) providing a second transducer within the monitored space for converting audio signals into second analog electrical signals;k) converting the second analog electrical signals into corresponding second digital signals; andl) receiving a current second digital signal sample S20 at periodic sampling intervals;m) storing n second digital signal samples S20, S2−1, S2−2, S2−3, . . . , S2(n-1) corresponding to the second digital signals received during the most recent n periodic sampling intervals, wherein n is an integer greater than 50, wherein S20 is the second digital signal sample received during a current sampling interval, wherein S2−1 is the second digital signal sample received one sampling interval before, wherein S2−2 is the second digital signal sample received two sampling intervals before, wherein S2−3 is the second digital signal sample received three sampling intervals before, and wherein S2(n-1) is the second digital signal sample received n−1 sampling intervals before;n) multiplying second digital signal sample S20 by at least one of second digital signal samples S2−1, S2−2, S2−3, . . . , S2(n-1) and accumulating the product of such multiplication in a first accumulator over a plurality of periodic sampling intervals to produce a first accumulated sum;o) multiplying second digital signal sample S20 by at least another of second digital signal samples S2−1, S2−2, S2−3, . . . , S2(n-1) and accumulating the product of such multiplication in a second accumulator over a plurality of periodic sampling intervals to produce a second accumulated sum;p) storing values for the first and second accumulated sums obtained when the monitored space is not disturbed;q) comparing current values for the first and second accumulated sums to the stored values for the first and second accumulated sums; andr) creating an alarm signal when the current values for the first and second accumulated sums do not correspond to values stored in step p).
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