Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1996-08-30
1998-11-03
Hofsass, Jeffery
Communications: electrical
Condition responsive indicating system
Specific condition
340566, 340544, 340522, 340541, 73658, G08B 1300
Patent
active
058315284
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a glass break detector for detecting the shattering of glass as well as a method used by a glass break detector for detecting the shattering of glass.
BACKGROUND OF THE INVENTION
There are a number of existing glass break detectors, however, to date these detectors have not been entirely effective. The most significant problem to be solved by a glass break detector is the elimination of the occurrence of false alarms. Most of the prior art glass break detectors have recognized that there are low frequency components of a glass break signal. These low frequency components are often referred to as the "thud" associated with the initial force which leads to flexure of the glass and the subsequent shattering of the glass. The low frequency vibration of the glass and the subsequent low frequency vibration of the surrounding supporting structure, typically the glass frame, dominates these components. The prior art has also recognized that there are high frequency components between 4 kHz and approximately 8 kHz.
Some of the prior art systems have tried to categorize the glass break event by analyzing the amplitude and/or frequency of the signal. Some of these prior art structures have focused on a portion of the glass break signal at approximately 6.5 kHz while other systems have looked to timing relationships between the low frequency "thud" components and higher frequency components of a predetermined amplitude. The main problem with the prior art is the inability of the system to distinguish glass break events from non-glass break events. Common false alarms are caused by thunder, dropping metal objects, ringing of bells, service station bells, chirping birds, slamming doors, splintering wood and mouse traps. These sources have both low frequency components and high frequency components somewhat similar to a glass break event.
An improved alarm detection arrangement for detecting glass breakage is proposed herein which is more reliable and can more readily distinguish glass break events from many non-glass break events which previously caused false alarms.
SUMMARY OF THE INVENTION
A glass break detector according to the present invention detects the breaking of glass based on the non-deterministic characteristics of high frequency components of the signal and other characteristics which distinguish the signal from non-glass break transient events.
A glass break detector, according to an aspect of the present invention, detects the breaking of glass and comprises an acoustic transducer which is capable of producing a wide-band electrical signal, a processing arrangement for removing low frequency components and identifying changes in the electrical signal caused by a transient high amplitude non-deterministic signal, and an alarm arrangement which produces an alarm signal when a transient high amplitude non-deterministic signal is detected.
According to a preferred aspect of the invention, the processing arrangement of the glass break detector, includes an initial high-pass filter for eliminating low frequency components below about 1 kHz.
A glass break detector, according to the present invention, comprises an acoustical transducer responsive to acoustic pressure and, based thereon, produces an electrical output signal, a filter for removing low frequency components of the output electrical signal typically associated with the initial force leading to a glass break event and passing high frequency components of the output electrical signal, and a processing arrangement which uses statistical techniques for analyzing the high frequency components of the output signal for characteristics indicative of a glass break event and which collectively distinguish the output from non-glass break events, and producing an alarm signal when said characteristics are present.
According to a preferred aspect of the invention, the glass break detector includes a reference signal as part of the processing means which is cross-correlated with the higher frequency com
REFERENCES:
patent: 3717864 (1973-02-01), Cook et al.
patent: 3863250 (1975-01-01), McCluskey, Jr.
patent: 3889250 (1975-06-01), Solomon
patent: 3955050 (1976-05-01), DiToro
patent: 4030089 (1977-06-01), Wurfel
patent: 4054867 (1977-10-01), Owens
patent: 4088989 (1978-05-01), Solomon
patent: 4091660 (1978-05-01), Yanagi
patent: 4134109 (1979-01-01), McCormick et al.
patent: 4196423 (1980-04-01), Carver et al.
patent: 4668941 (1987-05-01), Davenport et al.
patent: 4837558 (1989-06-01), Abel et al.
patent: 4845464 (1989-07-01), Drori et al.
patent: 4853677 (1989-08-01), Yarbrough et al.
patent: 4929925 (1990-05-01), Bodine et al.
patent: 5117220 (1992-05-01), Marino et al.
patent: 5192931 (1993-03-01), Smith et al.
patent: 5229748 (1993-07-01), Ehringer et al.
patent: 5341122 (1994-08-01), Rickman
patent: 5376919 (1994-12-01), Rickman
patent: 5414409 (1995-05-01), Voosen et al.
patent: 5510765 (1996-04-01), Madau
patent: 5510767 (1996-04-01), Smith
Cecic Dennis
Fong Hartwell
Digital Security Controls Ltd.
Hofsass Jeffery
Lee Benjamin C.
LandOfFree
Detection of glass breakage does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Detection of glass breakage, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Detection of glass breakage will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-694126