Analysis of acoustic data acquisition instrumentation for underwater blast dredging

A team of seniors from the University of Rhode Island were tasked with analyzing the acoustic data and evaluating the data acquisition systems used in Pacific Northwest National Laboratories’ (PNNL) study of blast dredging in the Columbia River. Throughout the semester, the students learned about the unique acoustic signatures of confined underwater blasts and the necessary specifications of systems used to record them. PNNL used two data acquisition systems. One was a tourmaline underwater blast sensor system created by PCB Piezotronics. The second was a hydrophone system using a Teledyne TC 4040 hydrophone, a Dytran inline charge amplifier, and a signal conditioner built for the blast sensor system. The students concluded that the data from the blast sensor system was reliable because the system was built by the company for this specific application and there were calibration sheets showing the system worked properly. The hydrophone data was deemed unreliable because components were orientated in an unusual manner that lead to improper data acquisition. A class of URI graduate students built a new hydrophone system that accurately recorded underwater dredge blasts performed in New York Harbor. This system is a fraction of the price of the blast sensor system.