Fact 1: Blowing air into a whistle causes air to vibrate inside the whistle.

Fact 2: Pipe organ Vibrating columns of air inside the pipes are the sound source.

Given the two facts above, answer the question "blowing air into a whistle causes a what?" with the following options: 
- rapid blast of heat
 - kinetic energy
 - little beads
 - activation energy
 - sound source
 - wind speed
 - small rattling
 - mechanical


 

     sound source    