"RAIN BIRD" TONGUING

I frequently tell students, “tongue like a Rain Bird sprinkler.” I am not alone.

Impact sprinklers, like the Rain Bird® (or Aqualine), derive their energy from the impact of a steady stream of water. That energy is stored in the spring when the arm bounces off the water – the water pushes it back – ​over and over. If the water stops, so does the arm. The water does the work.
 
Our tongue can be like the spring – it can store energy from the airstream – the air can do much of the work. If the airstream is inadequate, our tongue must make two movements, both to and fro – doing all the work. Also, the Bernoulli principle and the Venturi effect are involved. Moving air lowers air pressure and the tongue is "sucked" back towards the closed position – not unlike embouchure function. If the airstream is sufficient and steady, the air will do about ½ the work, moving the tongue back, and we can tongue faster and more relaxed. (This similar to, but not the same as, flutter-tonguing.)

Tongue with the sprinkler, not the faucet – constant, steady airflow!