Derick can hit an A note by blowing very soft or by blowing very hard. By changing how hard he blows into the trombone Derick is changing how loud the note is. Which property of waves is he changing w?

Derick is changing the amplitude of the wave by blowing either very soft or very hard into the Trombone. Amplitude in a wave is the measure of the maximum disturbance in the medium from its undisturbed position. By blowing harder, he is increasing the maximum disturbance which corresponds to a louder sound.