Slinky sound wave

Sound travels as a longitudinal wave, where all the molecules of the medium vibrate in the same direction of travel. Different sounds are produced by changing the characteristics of the sound wave, such as frequency and amplitude. 

The amplitude or height of a sound wave determines its loudness or volume. A loud sound is associated with a tall wave, and a quiet sound is associated with a short wave. 

The pitch of a sound is determined by the frequency or the number of cycles per second a sound wave repeats itself. A high-pitched sound is associated with a high frequency wave, while a low-pitched sound corresponds to a low frequency wave. The following activity will help students visualize sound properties.


  • Slinky
  • Watch this: Slinky demonstration of longitudinal and transverse waves.

Estimated time

5 mins


Longitudinal wave

  1. Ask for two volunteers to help demonstrate. Each will hold one end of the slinky and stretch it out on the ground.
  2. One person will hold their end steady, the other volunteer will push their slinky forward towards the opposite end in a parallel motion to the ground. Ask the students to observe the movement of the wave and what happens to the slinky’s coils. Note the areas where the coils are tightly together and areas where they are more spread out. 
  3. Test out different speeds. Have them try a quick push and a slow one. Tell them to keep track of the wave movement.

Transverse wave 

  1. Now, have the volunteers switch roles. The volunteer who held the steady end in the first demonstration will now be the one to create the next wave, and vice versa.
  2. Instruct the volunteer creating the wave to move the slinky side to side on the floor to demonstrate a transverse wave.
  3. Encourage them to experiment with creating waves of different heights: big waves for loud sounds, and short  waves for quiet sounds. Additionally, you can ask them to use their voice to represent the different volumes.
  4. Have them experiment with creating waves at different speeds: fast waves for high pitched sounds, and slow waves for low sounds. Again, you can ask them to simultaneously use their voice to represent the different pitches.
Illustration of a longitudinal wave with a slinky in a straight line but where one region is compressed and one region is elongated.
Longitudinal wave.
Illustration of a transverse wave with a sinky making an up and down, or sideways S, shape.
Transverse wave.

What is happening?

Longitudinal wave: In the first demonstration, the slinky illustrated the parallel direction in which sound waves propagate from their source. As sound waves move through a medium, their energy causes the molecules to vibrate and bump into each other, resulting in areas of compression and expansion.

Transverse wave: In the second demonstration, the slinky was used to create a transverse wave. This helps students visualize the shape of a wave and understand that the different properties of sound waves lead to diverse sounds. The wave height, or amplitude, influences the volume of a sound, and the frequency determines the pitch. 

Wrap-up questions

  • Describe what happens to the slinky when you push it forward.
  • Can students produce:
    • A loud, low pitched sound
    • A quiet, high pitched sound
  • For older students, can they produce:
    • A high frequency sound
    • A  short amplitude sound

Why is this important?

The frequency and volume of sound directly affect the distance it travels. Lower pitch and louder sounds travel further than higher pitch and quieter sounds. In the study of underwater noise, it’s important to understand how different sounds propagate in the ocean and their potential impact on marine species.