Visible Effects of the Invisible

“Visible Effects of the Invisible” graphically demonstrates resonant frequencies. A horizontal, clear, glass tube is partially filled with clear fluid. Sound generated by a speaker housed at one end of the tube causes the air in the tube to vibrate and geysers appear in the fluid where the motion of air is greatest. The geysers are generated at various sections of the tube by the adjusting the resonant frequency of the speaker, causing pressure differentials.

Your ears collect sounds, process them, and send sound signals to your brain. The ear’s parts, the outer ear, middle ear and inner ear, all work together. The outer, the part that people can see, collects the sound waves. The outer ear also includes the ear canal, where wax is produced to protect the canal. After sound waves enter the outer ear, they travel through the ear canal and make their way to the middle ear. The middle ear’s main job is to take those sound waves and turn them into vibrations that are delivered to the inner ear. To do this, it needs the eardrum, which is a thin piece of skin stretched tight like a drum. The eardrum separates the outer ear from the middle ear and the ossicles, three of the tiniest, most delicate bones in your body. When sound waves reach the eardrum, they cause the eardrum to vibrate, which moves the tiny ossicles — from the hammer to the anvil and then to the stirrup. These bones help sound move along on its journey into the inner ear. Sound comes into the inner ear as vibrations and enters the cochlea, a small, curled tube in the inner ear that is filled with liquid, which is set into motion, like a wave, when the ossicles vibrate. When sound reaches the cochlea, the vibrations (sound) cause tiny hairs on the cells to move, creating nerve signals that the brain understands as sound.

Questions to Ask

Can sound waves travel without particles “touching” each other? How does sound move through the liquid?

What would happen to the geysers if the sound volume is increased?

Would the same effects be seen for a high pitch and a low pitch?

What type of sound would make the geysers rise and fall quickly—short bursts of high pitch or short bursts of low pitch?

Relevant Arkansas Science Frameworks

PS.6.3.1, PS.6.3.2, PS.6.3.3, PS.7.8.4, PS.7.8.6, PS.7.8.7, P.6.PS.13, P.7.PS.5

"Mini-Vibe" — An activity to do at home or in the classroom