That’s also true for guitar strings-the higher-pitched strings are more tightly stretched strings. The tighter they’re stretched, the higher the pitch. We adjust the pitch of our voice to sing a high note or a low note by adjusting the tightness of our vocal folds. The vocal folds of children are much shorter than those of adult males and females, so children’s vocal folds vibrate faster, producing a higher-pitched voice. Adult male voices are usually lower pitched than female voices due to longer and thicker vocal folds. Men and women have different size vocal folds. (See the link to a brief description of vocal folds in the Internet Resources.) Students can feel the vibrations from their vocal folds if they put their fingers on their throat while humming a low-pitched tone. These are commonly called vocal cords, although a better name for them is vocal folds, as they are not cords. When we speak or sing, there are folds of tissue in our throat that vibrate.
That vibrating wood has a large area, so it hits a lot of air molecules, producing a lot of vibrations in the air, i.e., a lot of sound. However, the vibrating string causes the wooden body of the guitar to vibrate. The string itself doesn’t make a whole lot of sound because the string is very thin and doesn’t hit many air molecules as it vibrates. When you pluck a string on an acoustic guitar, it vibrates. Do some of your students play a musical instrument? They all involve vibrations. (Goggles are necessary when working with rubber bands.) It vibrates and makes a sound. What other examples can students come up with that demonstrate vibrations that make a sound? It could be as simple as stretching a rubber band between two fingers and then plucking it. The first thing students should conclude is that vibrations produce sound. If necessary, precede all this by a review of pitch.) The less the ruler was sticking out, the higher the pitch. What did they notice when they released the ruler? (The ruler vibrated, and it made a sound.) How did the sound change when there was a different amount of the ruler hanging off the edge? (The more of the ruler that was past the edge of the table, the lower the pitch. Does each student have a science notebook or journal? Students can write down their observations and what they think is going on. Don’t forget…you can use science activities to have students practice their writing skills.