A Non-Contact Displacement Sensor for Estimating Sound Pressure Level in Pipes

The presence of noise in piping systems often serves as an early warning of mechanical problems such as faulty or cavitating pumps and valves, or boiling in cooling lines. Additionally, in many Naval environments, especially submarines, minimizing noise radiated from vibrating pipes is highly desirable. The ability to quantify the sound pressure level in fluid-filled pipes with an external sensor is needed. Creare proposes to develop an easy-to-use, modular optical displacement sensor to estimate the sound pressure level inside a pipe by monitoring the outer wall vibrations. The sensor will be sensitive to sound pressure levels between 100 and 120 dB relative to 1 micro-Pascal at all frequencies between 10 and 3,000 Hz. In Phase I we will optimize our existing models of sound propagation in fluid-filled pipes and optical displacement sensors for pipes and fluids of interest to the Navy, perform a simple benchtop experiment to demonstrate the feasibility of our approach, and use the results of the models and experiments to refine our estimate of system sensitivity. By the completion of Phase II we will have developed a fully fieldable sensor system consisting of one universal control module and at least two pipe interface modules of different sizes.