Look at the tubes. Do you see that they are all a different length? The longer the tube, the lower the tone you hear.
When you hit the opening of the tube with a slipper, you make the tube and the air inside it vibrate. That vibration then moves through the air, to your eardrums. They start to vibrate too and that is how you hear sound.
If the tube is long, it takes a long time for the vibrations to move from the opening to the end of the tube and back. This causes the air in the tube to vibrate slowly which is why you hear a low tone. If the tube is shorter, a trip back and forth doesn’t take as long. The air vibrates faster, so you hear a high tone.
Tubes of different lengths on a pan flute
A pan flute too consists of a lot of tubes of different lengths. If you blow on the long tubes, you will get a low tone. If you blow on the short tubes, you will get a high tone.
If you leave the holes of your recorder open, the air can already escape from the first open hole. This makes for a ‘short’ tube’ which produces a high tone. If you close the holes of the recorder with your fingers, you make the tube ‘longer’ and you will get a lower tone.
