Wow, neat, Instructables user nusnel shows us how to make an acoustic rain gauge:

For a project at Delft University of Technology (The Netherlands) we are building cheap, durable acoustic rain gauges, known as disdrometers. These devices “listen” to the rain and calculate the rain rate from the acoustic signal. But you can also listen to the signal: that way, you can hear the rain, even when inside a cubicle. A nice way to bring the outside environment into the office, without getting wet.