A Hail Size Distribution Impact Transducer
  An active impact transducer has been designed and tested for the purpose of monitoring hail fall in the vicinity of the Space Shuttle launch pads. An important outcome of this design is the opportunity to utilize frequency analysis to discriminate between the audio signal generated from raindrop impacts and that of hailstone impacts. The sound of hail impacting a metal plate is sub-tly but distinctly different than the sound of rain impacts. This useful characteristic permits application of signal processing algorithms that are inherently more robust than techniques relying on amplitude processing alone in the implementation of a hail disdrometer. 
John E. Lane, Robert C. Youngquist, William D. Haskell, and Robert B.   Cox
physics.ao-ph astro-ph.IM