We are all used to hearing different sounds. We describe the differences in various ways: loudness (loud, noisy, quiet, etc.) and high or low pitch.
One way of investigating differences in sound is to use a microphone connected to an oscilloscope. The microphone turns sound waves into an alternating electrical voltage which the scope displays on a screen:
The taller the amplitude, the louder the sound. The more waves there are displayed, the higher the pitch. Let's look at this in more detail.