Systems and methods for acquiring and characterizing time varying signals of interest

Abstract

Methods or systems for identifying seismic or acoustic signals of interest originating with moving motorized vehicles or footstep movement or stationary or moving machinery. A related system for monitoring an area includes a plurality of sensing devices each comprising a frame and a piezo-electric sensor element. A monitoring device is coupled to receive information from each of the sensing devices. One method includes providing a processing chain coupled to receive signal data from a sensor device which receives the signals, including a detection stage, a Joint Time Frequency (JTF) domain stage, and a classification stage. The detection stage identifies presence of signals that emerge from the background. The JTF domain stage estimates the state of the signals of interest over time. The classification stage assesses the previously derived information to form a decision about source identity. In one embodiment, the detector stage performs detections on a single cycle basis.

6 . A sensing system responsive to acoustic or seismic signals, comprising:
 a frame; and   a piezo-electric sensor element, responsive to a wavefield of seismic or acoustic energy, positioned about the frame, wherein coupling between the piezo-electric sensor element and the frame is so limited as to render direct coupling of the piezo-electric sensor element with signals of the wavefield the predominant means for stimulating the piezo-electric sensor element with seismic energy.   
     
     
         7 . The system of  claim 6  wherein the element is in the form of a coaxial cable comprising a polymer material having piezo-electric properties positioned between conductors to generate a charge differential measurable as a voltage between the conductors. 
     
     
         8 . The system of  claim 6  wherein the sensor element is responsive to strain in multiple modes one or more modes taken from the set consisting of d 31 , d 32  and d 33 . 
     
     
         9 . The system of  claim 6  wherein the frame and piezo-electric sensor element form a first sensing device, the system further comprising:
 one or more additional sensing devices each comprising a frame and a piezo-electric sensor element, responsive to the wavefield, positioned about the frame; and 
 a monitoring device coupled to receive information from each of the sensing devices. 
 
     
     
         10 . The system of  claim 9  configured to generate classification information based on data acquired by one or more of the sensing devices. 
     
     
         11 . The system of  claim 10  wherein:
 the sensing devices are configured as a coordinated array; and 
 the monitoring device performs coherent processing of data acquired by the array of devices. 
 
     
     
         12 . A method of forming a sensing system responsive to signals in a wavefield of seismic or acoustic energy, comprising:
 positioning a piezo-electric sensor along or about a frame with an intermediate layer therebetween so that the piezo-electric sensor is in an entirely spaced-apart relation to the frame, the frame having a surface to which the piezo-electric sensor is stabilized , the spaced-apart relation between the frame and the piezo-electric sensor resulting in a seismic or acoustic isolating gap which decouples transmission of wavefield energy from the frame to the piezo-electric sensor,   whereby decoupling of seismic or acoustic signals between the frame and the piezo-electric sensor renders the piezo-electric sensor more responsive to direct coupling with the wavefield of seismic or acoustic energy, based on direct incidence of the wavefield on the piezo-electric sensor, and renders the piezo-electric sensor less responsive to wavefield energy received by the frame and then transmitted from the frame to the piezo-electric sensor.   
     
     
         13 . The method of  claim 12  further including positioning an intermediate layer between the frame surface and the foil layer to so limit mechanical coupling between the sheet and the frame as to render the direct coupling of the sheet with the wavefield the predominant means for stimulating the sensor element with seismic energy. 
     
     
         14 . A method of sensing acoustic or seismic signals with a system comprising a frame and a piezo-electric sensor element positioned about the frame and responsive to a wavefield of seismic or acoustic energy, comprising:
 limiting coupling between the piezo-electric sensor element and the frame to render direct coupling of the piezo-electric sensor element with signals of the wavefield the predominant means for stimulating the sensor element with seismic energy.