As the end of the straw is cut one inch at a time, the pitch goes up. It took me a while to figure out how far I should place the straw into my mouth to get the sound. I get a good sound with about 2-3 inches inside my mouth. Cutting the straw in this manner creates a reed much like the ones used in wind instruments. By blowing through the reed, the ends vibrate creating sound.
Pitch is related to how long the vibrating column is.
The longer the column, the lower the pitch. You can further demonstrate this concept by blowing into a test tube with varying amounts of water. The longer the air column above the water, the lower the pitch. Index of Activities . This activity is featured in Future Flight Hawaii , a K-12 Education Project of Hawaii Space Grant Consortium.