Depends where you stick them on. I am using them in my diy raingauges and one of my first prototypes had a too thin surface (where the raindrops fall on) causing a light rainshower on my graph when someone was talking within a metre or 2.
It doesnt add anything. It replaces all mechanical stuff and makes the gauge maintenance free. An ESP8266 translates the sound of the raindrops to an amount. My first prototype is still running fine after 5 years outside.
