Doppler Effect of Sound Waves in Air
The program shows sound waves in air and demonstrates the Doppler effect/shift. Click a green flag to start. You can change the speed and rotation of the rocket by dragging the sliders or using the arrow keys. The speed of sound seems to be about 80 pixels per second in this medium and if you go above this you are breaking the sound barrier.
There is a game in the first 3 minutes since green flag. Each time a wave hits the microphone it makes a popping sound or a laser sound. You earn points for pops and lose points for lasers and a louder sound gives or loses more points. The pops are in the first 2 seconds since silence broke and the laser between 2 and 6 seconds. You click the mic to move it to a random location. You probably get a higher point by flying at about Mach 1 speed and surprise the mic with many waves at once.
The frequency of the sounds is proportional to the sound frequency you would hear if the rocket had a siren.
It was done from scratch using clones for the wave fronts that fade out and are deleted. You may want to read https://en.wikipedia.org/wiki/Doppler_effect .
You can view the code at: http://scratchblocks.github.io/generator/#project=12532039