Lucas Lezamiz, a mechanical engineering graduate student at the UW, led two Seattle-area high school physics classes in studies of rainfall estimation derived from hydrophone data. Introduction Using an underwater hydrophone and a webcam above the water's surface, the SORFED (SOund Recording For EDucation) website displays stored ambient noise data collected in Lake Union. Users can explore the sound signatures of different weather events and human activity on the lake by listening to audio clips side by side with video from the webcam. The website was used as the primary tool to teach high school students in Seattle how to estimate rainfall by listening to underwater noise. Students worked in teams to calibrate underwater noise to rain rate, then used this relationship to estimate rain rate as a function of time on other days based on the noise level recorded in the lake. Total rainfall was then found by integration. Sound Signatures Weather events and human activity on Lake Union have characteristic sound signatures. Boats appear as discrete spikes Rain appears as a gradual increase in the noise floor With some fairly simple assumptions, we can learn a lot about human activity and the environment on the lake Measuring Rainfall High school students explored concepts in physics and calculus by using underwater noise to estimate rainfall. First, a clean sound signature was captured using the SORFED website on a rainy Seattle night. The sound signature was then related to precipaitation using local weather data from various locations. Assuming a linear correlation over the rain rates measured, students derived mathematical expressions for rain rate as a function of underwater noise level. RR (in/hr) = 0.0051 (NL) + 0.2593 Students were then introduced to the concept of signal-to-noise ratio (SNR) by using their equations to predict rain rate on other rainy days; one with relatively little activity on the lake, and another dominated by boat noise. Since the derived rain rate equation attributes all noise (e.g., that of a passing ship) to rain, the value of rain rate at any given time is unreliable. Students learned that by integrating to get the area under the curves, however, fairly good estimates of the total rainfall can be obtained. Using similar techniques students can explore other topics of interest, including shipping rate estimation, wind speed prediction, SNR studies, and spectral methods. Lucas's advisor at APL-UW is Principal Physicist Kevin Williams. Lucas presented a poster (PDF, 1.4 MB) on how to lead high school students through problems in applied acoustics at the fall 2006 Acoustical Society of America meeting in Honolulu, HI. High-resolution examples of the images on this page and more are available in the poster.