Abstract:
A glassbreak detector first and second different audio transducers. One transducer is omnidirectional. The other is highly directional. Control circuitry processes signals from both transducers and determines if a glassbreakage profile is present.

Description:
FIELD 
       [0001]    The application pertains to glassbreak detectors. More particularly, the application pertains to such detectors which include highly directional audio transducers. 
       BACKGROUND 
       [0002]    Glassbreak detectors are commonly used, to provide environmental feedback as to the condition of windows, in security systems which are intended to monitor a predetermined region. Despite their usefulness, they at times have problems with false alarms which occur from displaced locations which are in a different direction than the window being protected. This is because they commonly use a microphone which is omni-directional by design, resulting in the detector being sensitive to sounds occurring from any direction. Although uni-directional microphones are available, they are designed in manner that makes it difficult to distinguish the direction from which an unidentified sound is originating. 
         [0003]    In a known prior art implementation of a glassbreak detector, a time of arrival method is implemented using two omni-directional microphones. The microphones are arranged opposed to one another on the order of 180 degrees. This configuration forms a protected zone and an excluded zone. Signals from the two microphones can be processed to detect sounds of glass breaking from the protected zone. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  is a block diagram of a detector which includes a highly directional audio transducer; and 
           [0005]      FIG. 2  is a flow diagram illustrating one form of operation of a detector as in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0006]    While disclosed embodiments can take many different forms, specific embodiments thereof are shown in the drawings and will be described herein in detail with the understanding that the present disclosure is to be considered as an exemplification of the principles thereof as well as the best mode of practicing same, and is not intended to limit the application or claims to the specific embodiment illustrated. 
         [0007]    In accordance herewith, a glassbreak detector that is highly sensitive to the direction the sound is coming from incorporates both an omnidirectional audio transducer, such as an omnidirectional microphone, and a highly directional audio transducer. Additionally, the device can be installed so that it is “aimed” towards the window(s) being protected. As a result, false alarms can be reduced. Another embodiment can be used to identify the location and/or movements of room occupants for high security applications. 
         [0008]    In one embodiment, highly directional mems-type acoustical sensors, known as microflowns, could be used in conjunction with an omni-directional microphone. This combination results in a glassbreak detector with reduced susceptibility to false alarms, and, achieves a high degree of detection when the protected windows are subjected to forced entry. This detector could be installed in a room “aimed” at the window(s) it is intended to protect, and would be programmed to identify the origin direction of sound events to be processed. It could also determine if acoustical characteristics of an event were indicative of a forced entry through the protected window(s), or a false alarm. An alarm event can be communicated to an alarm panel using known methods. 
         [0009]      FIG. 1  is a block diagram of an embodiment of an environmental condition detector  10 , for example a highly directional glassbreak detector, in accordance herewith. Detector  10  has a housing  12  which carries a plurality of electronic components. 
         [0010]    Detector  10  includes at least two audio sensors  14   a    14   b . One sensor  14   a  can be implemented, for example as an omnidirectional microphone and buffer circuits. The second  14   b  can be implemented as a highly directional audio transducer such as a microflown-type mems sensor. Buffered outputs from the sensors  14   a ,  14   b  can be coupled to analog signal conditioning circuitry  16   a ,  16   b.    
         [0011]    Conditioned analog, or digital, outputs from one or both circuits  16   a ,  16   b  can be coupled to comparator circuits  18 , and/or to control circuits  22 . Control circuits  22  can include the comparator circuits  18 . Control circuits  22  could be implemented, at least in part, with a programmable processor  22   a  and pre-stored control programs  22   b  stored on non-volatile storage circuits  22   c.    
         [0012]    Control circuits  22  are also coupled to user input circuits  26  which enable a user to specify installation parameters or conditions. A program, debug and test interface  28 , coupled to control circuits  22 , facilitates initial programming, debugging and testing of the detector  10 . The interface  28  can be used after installation to evaluate parameters or other data stored in the non-volatile circuits  22   c . For example, results of tests or installation of the detector  10  can be stored in circuits  22   c  for subsequent retrieval and evaluation. 
         [0013]    Local status indicators  30 , for example, audible or visual indicators such as audio output devices, LEDs, liquid crystal displays or the like, are coupled to circuits  22  and activated thereby to provide local status information. Status communication circuitry  32 , coupled to control circuits  22 , provides wired or wireless communication with a displaced regional monitoring system S as would be understood by those of skill in the art. 
         [0014]      FIG. 2  illustrates exemplary aspects of processing  100  at the detector  10 . In response to detecting an event-indicating interrupt, as at  104 , the control circuits  22  can acquire and convert, as at  106 , one or more input signal values, from sensors  14   a ,  14   b . Those signals can be processed, as at  108 , including evaluating directional information relative to transducer  14   b  as at  110 , and categorized as to type of event, as at  112 . 
         [0015]    An alarm event can generate an alarm communication, as at  116 , either locally, via output devices  30 , or via communications interface  32 . False alarms can advantageously be detected and rejected. 
         [0016]    A detected set-up event can be evaluated to determine if installation had been carried out as expected. Installation setup data can be stored in, loaded into, memory  22   c . A local indication thereof can be provided, as at  124  via output device(s)  30 . 
         [0017]    Events can be logged, not shown, and stored in non-volatile memory  22   c  for after-installation review. Data, for example, one or more operational parameters, installation and setup data, along with information relative to logged events can be retrieved from the memory  22   c  and output via the local interface  28 , local indicators  30 , or communications interface  32 . 
         [0018]    The pre-stored operational parameters, setup, or installation, data make possible after-installation reviews to evaluate the operation of the detector  10 . Where a detector, such as  10 , has failed to perform as expected, such pre-stored information may be the only indicia as to the field condition of the unit. Advantageously, all such data, without limitation, can be detected and stored in real-time and subsequently retrieved. 
         [0019]    It will be understood that other types of sensors including position, thermal, smoke, infra-red, smoke gas or flame sensors can be incorporated into detector  10  and all come within the spirit and scope hereof. The specific details of microphones, audio transducers or other types of sensors are not limitations hereof. 
         [0020]    From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims. Further, logic flows depicted in the figures do not require the particular order shown, or sequential order, to achieve desirable results. Other steps may be provided, or steps may be eliminated, from the described flows, and other components may be add to, or removed from the described embodiments.