Lo Noise Infrasonic Sensor System

The project goal is to develop an alternative infrasound monitoring system with piezoelectric sensors for use under the Comprehensive Test Ban Treaty. These sensors will have several advantages over the microbarograph system that forms the baseline forthe IMS. As an all-electronic system, the novel sensor would be far simpler than the baseline, with no moving parts or piping. It will be more robust and durable, less expensive, and more flexible in its design and capabilities. For example, electronicsignals do not experience delay so that subelements can be at any distance from processing unit. In Phase I, it was demonstrated that off-the-shelf PVDF piezocable could be used as an infrasound sensor but conformity with the Treaty noise specificationcould not be demonstrated. The potential reasons for this are understood. In Phase II, a revised system meeting the specifications will be developed through a combination of lower electronic amplifier noise and higher acoustic sensitivity with highsensor capacitance. This may require a change of sensors to a modified piezocable, series combinations of multiple cables or the use of PVDF cylinders. A prototype, optimizing signal and noise, suitable for the IMS application will be developed anddemonstrated in a field test. An all-electronic piezoelectric infrasound ISM array alternative would be less complex than the present design and will provide many advantages. The simpler array would likely be less susceptible to environmental factors,lower in cost both to purchase and maintain, more reliable, easier to replace, and possibly less visible and thereby less susceptible to vandalism. It also offers the prospect of novel electronic processing. If individual subelements are monitored,arrays can beamformed to provide directionality. Similarly array sections that are noisy for any reason (e.g., due to animals or other highly local phenomena) can be identified and temporarily ignored in order to maintain the signal to noise ratio for theentire array. Beyond the CTBT applications, due to their simplicity, light weight, flexibility, and low cost, piezoelectric infrasound sensors become attractive for a number of military and civilian applications.