Once Maxwell introduced the concept of electromagnetic waves, everything clicked into place. air, water), but space is a near vacuum without enough molecules for sound waves to move through.Light waves come in a continuous variety of sizes, frequencies and energies, a continuum known as the electromagnetic spectrum. Have the students use the same kind of “human model” to act out high and low frequency sounds (more or fewer vibrations per second).Ĭan sound exist in space outside of the space shuttle? Hint: No. It’s a simple visual demo and allows for volunteer participation right away. Teacher Tip: This demonstration is a good way to introduce the topic of sound. Run through it a second time with more speed.The vibration continues down the line until it reaches the last student, who bangs the drum (eardrum) when the last air molecule reaches them.In the meantime, the second student returns to their original place. The third student, feeling the touch of the second student, starts to vibrate and move towards the fourth student.The second student (air molecule) begins to vibrate (wiggle), moves toward the third student (air molecule) and touches them.The first student rings the bell (or other sound-making device).Ask the students to act out the following sequence of events:.Place all of the volunteers in a line, facing the class, with 3–4 feet of space separating them.

4 students are air molecules between the source and the eardrum.

1 student is the eardrum (holding the drum).

1 student is the sound source (holding something that makes a sound, such as a bell).

Invite 5 or 6 students to the front of the class to be your volunteers.

Part 2: Illustrating Sound = Vibration, Vibration, Vibration

Can you hear the vibrations of your hands?.

What is this motion called (waving, shaking, jiggling, wiggling, etc.)? The scientific name for this motion is vibration.

Ask the students to wave their hands in front of their faces.

Part 1: Introducing the concept of vibration If a tree falls in a forest and there is nobody around to hear it, does it still make a sound? How many different vibrations are needed to hear a sound?Īll objects have the potential to vibrate. Cats can hear even higher frequencies than dogs, and porpoises can hear the fastest vibrations of all (up to 150,000 times per second).Īnything that makes a sound e.g. Animals can hear different frequencies from humans. The fastest vibration we can hear is 20,000 times per second, which would be a very high sound. The slowest vibration our human ears can hear is 20 times a second.

We cannot hear the vibrations that are made by waving our hands in the air because they are too slow. These vibrations enter the outer ear and cause the eardrum to vibrate too. The number of vibrations per second is known as the frequency, measured in Hertz (1 Hz = 1 vibration per second). When we hear something, we are sensing the vibrations in the air. There is a progression of collisions that pass through the air as a sound wave.Īir itself does not travel with the wave (there is no gush or puff of air that accompanies each sound) each air molecule moves away from a rest point and then, eventually, returns to it. When a sound is produced, it causes the air molecules to bump into their neighbouring molecules, who then bump into their neighbours, and so on. the molecules in the air (or another medium e.g.

Three things vibrate when sound is created: In this demonstration, students use their bodies to model vibrations that lead to sound waves.

Human frequency in waves persecond