Have you ever been to a concert and seen an American Sign Language interpreter signing the song lyrics alongside the performer? While it may seem unusual that someone who can’t hear a musical act would attend a concert, that’s actually an inaccurate supposition; thanks to the vibrations the music provides, deaf audience members can hear the music pretty well! But how does this happen? Aren’t vibrations something you feel, not something you hear? During today’s investigation, you will experience how sound moves and is received by listeners.
While the history of “sound science” is broad and many famous scientists have made important contributions, it is Leonardi DaVinci who is generally credited with discovering that sound actually travels in waves. However, in the 17th century, Galileo made great advancements into how we perceive sound and how sound travels. He found out about frequency of sound, and how that determines pitch. If the vibrations of a sound happen far apart, the sound will have a low frequency and sound deep. If the vibrations are close together, that will create a high-pitched sound. The way that humans perceive these vibrations is something we will explore in this experiment.
You should feel the balloon vibrate when you make noise. The intensity of the vibrations should change based on how loud the noise is, and the pitch the noise is. This happens because sound travels in waves. Sound waves are what are called longitudinal waves, which means it travels in the same direction as the disturbance that caused it. Sound is caused by something vibrating, which compresses and stretches the air around it, which vibrates your ear drum, and your brain interprets that vibration as sound. The interesting thing about this experiment is that you can feel those vibrations with your hands instead of just hearing them as sound. Think about where the vibrations from step three came from. Are those similar or different to the vibrations from step six?
Make sure to clean up when you are done. Pop the balloon and throw it away. Turn off your speaker system to conserve electricity.
Think about other situations where you have felt sound. Have you ever been able to tell a car was playing music before it even drove down your street? How do you think sound travels through different materials, like water or metal? Is there a way you could test your guesses? Are balloons the best object to feel sound through? See if you can find a different object that acts like a balloon when you make noise near it.
This experiment was selected for Science at Home because it teaches NGSS Disciplinary Core Ideas, which have broad importance within or across multiple science or engineering disciplines.
Learn more about how this experiment is based in NGSS Disciplinary Core Ideas.