the pitch of the cell phone ringing will remains same when the amplitude of a sound wave increases.
The pitch of a sound wave depends on its frequency. more frequency means higher pitch and less frequency means lower pitch. The amplitude of wave is the maximum displacement of the particles of the medium from their mean positions. Increase in amplitude will increase the loudness and not the pitch. So the pitch remains same as the amplitude of sound wave is increased.
It is called observation because you observe with your nose by semlling things your eyes by looking at things your ears by hearing things your tongue by tasting things and your hands by feeling things