Science at Home

Science at Home: Good vibrations!

This Month we’re going to create an at home version of an exhibit we have at the museum and explore sound waves and resonance at the same time. We’re going to build a Chladni plate.

First a little background: Sound is made up of vibrations called sound waves that we hear. Lower sounds or lower pitches are caused by things vibrating slowly. As vibrations sped up the pitch or sound gets higher.  Different objects will vibrate at different speeds or frequencies. Ernst Chladni was a scientist in the 1800’s who discovered a really cool way to “see” these frequencies. He put a lot of salt on a metal plate and then drew a violin bow down the edge so that the plate vibrated. He found that the vibrations caused the salt to form different patterns and that different frequencies made different patterns appear. This type of experiment is usually called a chladni plate because of his discovery.  We have a Chladni plate on our museum floor that lets you change frequency and see different patterns but you can also do this at home:

 

Here’s what you need:

  • Large glass bowl
  • Parchment paper (large enough to cover the bowl)
  • Large rubber band
  • Salt or other fine powder
  • A bluetooth or wireless speaker that will fit in the bowl
  • Something that can connect to the speaker
  • Zip top bag (optional)
  • Food coloring (optional)

 

Before you begin, it is helpful to color the powder. You can skip these next steps if you want to get straight to the experiment but it will make it easier to see some of the patterns.

To dye your salt:

  1. Add a cup of salt to the zip top bag.
  2. Add a few drops of food coloring. The more food coloring you add, the more vibrant it will be but if you add too much then the salt will clump together.
  3. Remove all of the air from the bag and seal it.
  4. Knead the salt and food coloring until it is evenly spread.

Once you have your colored salt or are ready to begin seeing some frequencies we can start to build our Chladni plate.

  1. Place the speaker inside the bowl (making sure that it is on).
  2. Cover the top of the bowl with parchment paper and secure it with the rubberband.
  3. Sprinkle your salt or fine powder in an even layer over the top of the bowl.
  4. Try playing some music and see what happens! If you want to see really nice patterns start to show up, try playing single notes using a tuner app. Low notes and high notes will look very different.

Try experimenting and see what you find! Are there some notes that give crazy patterns? Share them with us at #smwv!

 

Developed by Hannah Weiss and Koren Smith