Glass breakage detector

A method of analyzing a sound produced by an event comprising:

• sensing the sound and producing an electrical sound signal characteristic of the sound;
• producing a plurality of frequency band-limited signals from the electrical signal;
• and
• characterizing the event by comparing at least one characteristic value derived from the band-limited signals with a first range of values and with a second range of values, said second range of values being wider than said first range of values wherein the event is characterized as a glass-breakage event if the characteristic value is within the first range of values, is characterized as a non-glass breakage event if the characteristic value is outside the second range of values and is characterized as an event which is to be further analyzed to determine whether a glass breakage event has occurred if the characteristic value is within the second range of values but outside the first range of value.

A method of determining whether a sound is generated by falling glass comprising

• sensing the sound and producing an electrical signal characteristic of the sound;
• producing a plurality of frequency band-limited signals from the electrical signal including at least one band-limited signal having a high frequency range characteristic of falling glass and one lower band-limited signal which is not characteristic of falling glass;
• and
• integrating the high frequency band-limited signal to form an integral signal during at least a portion of a time period during which sound characteristic of falling glass in a glass breakage event is expected to occur, and comparing the integral signal with a threshold value to identify whether a glass breakage event has occurred.

Apparatus for analyzing a sound produced by an event comprising:

• a sensor which senses the sound and produces an electrical signal characteristic of the sound;
• means for producing a plurality of frequency band-limited signals from the sound signal;
• rate-of-rise determining circuitry which receives the band limited signals and determines when a normalized rate-of-rise of at least two of the plurality of the band limited signals is above a respective given value specified for the particular band-limited signal;
• and
• a signal analysis system which identifies the signal as a signal which is to be further analyzed to determine whether glass breakage has occurred, said signal analysis system analyzing the electrical signal further only if a plurality of the band-limited signals have a normalized rate-of-rise greater than their respective given value during a predetermined time period.

Apparatus for detecting glass breakage utilizing the sound produced by an event comprising:

• a sensor which senses the sound and produces an electrical signal characteristic of the sound;
• means for producing a plurality of frequency band-limited signals from the electrical signal;
• and
• analysis circuitry which receives the band-limited signals and compares at least one characteristic value of the band-limited signals with a first range of values and a second range of values, said second range of values being wider than said first range of values, wherein an event is characterized as a glass-breakage event if the characteristic value is within the first range of values, is rejected as a non-glass breakage event if the characteristic value is outside the second range of values and the signals are passed to further analysis circuitry which further analyzes the signals to determine if the sound was caused by a glass breakage event.

Apparatus for analyzing sound to determine a breakage of glass comprising:

• a sensor which senses the sound and produces an electrical signal characteristic of the sound;
• means for producing a plurality of frequency band-limited signals from the sound signal including at least one band-limited signal having a high frequency range characteristic of falling glass and one lower band-limited signal which is not characteristic of falling glass;
• and
• analysis circuitry including an integrator which integrates the high frequency band-limited signal to form an integral signal during at least a portion of a time period during which sound characteristic of falling glass in a breakage event is expected to occur, said at least portion not including time periods during which the high frequency band limited signal is coincident with a signal from lower frequency band and comparing the integral signal to a threshold value.