WonderWorks: The Science of Sound

Sound is vibrations!

Today's Topic: The Science of Sound
Supplies:
wire/metal hangers
string
empty tin cans (with smooth-cut edges, not jagged)
balloons
ceramic or glass bowls (small is fine)
cling wrap (Saran Wrap or any other brand)
rice or some other small, not-flat grain-like substance
glasses (I used glass jars, but because they were different brands, even empty they made different tones when you tapped on them)
pitcher of water
metal spoons
empty tissue boxes (or any plastic containers small enough to stretch a rubber band around them)
rubber bands
variety of kid-friendly musical instruments -- especially nice are xylophones or other instruments in which it's easy to tell that the objects are making different tones because of their size (not just because of their relative levels of tension which is harder to see).


Book: 
  Sounds all around / Pfeffer, Wendy

(This book is a great introduction to the topic! I skipped over a few parts, but did cover sound waves, echolocation and decibels.)


The Inspiration (or "what I thought kids might do"):
make a "bell" out of a spoon 
...or a hanger
create a thin, taut surface to show how sound waves vibrate

 

Prep work: Although I didn't do this myself before class, I'd highly recommend that if you're going to use the balloons + tin can = drum idea, just make the drums before class.  Cut off the neck of a large, sturdy balloon (the kind you could fill with helium work well) and stretch it over the top of a can as tightly and as smoothly as you can, until tapping the top creates a nice, almost musical sound (rather than just the "thup, thup" of tapping a balloon).

Also, stretch some of the cling wrap over your glass or ceramic bowls.  Make sure it's as smooth and tight as you can make it.

What Kids Do:  While we were still in the circle reading the book together, it instructed all the kids to put their hands on their throats and say a word or sing a note and feel the vibrations and then to stop talking and feel how the vibrations sound. I thought this mini-experiment was an excellent introduction to the concept, but I failed to get any photos of it.

We had several stations set up around the room.  One station included rubber bands and a few things to wrap them around. This classic tissue box "guitar" had particularly unsatisfactory results, so for the second class....

 ....I dug out a few plastic containers from my supply closet and they stretched rubber bands across those.  Much better!

poke the tops of the tin can drums

 or stack them into the tallest drum ever!

 This family created this hybrid instrument which is played by pulling the rubber bands up high and letting them snap back down onto the can for a lovely PING noise.

Play with a few instruments :

 Try out "water xylophones..."

 Or... just pour the water back and forth...

 

This experiment worked sometimes and didn't work other times. We tried humming near the grains and sometimes they'd wiggle from the vibrations and sometimes they didn't.  I tried it myself and learned that (oddly) high and low pitches didn't work for me, but there was a mid-range pitch that resonated quite nicely.

 This clever experimenter discovered that the tin-can-drums could do the same trick.

 But my favorite experiment of the whole day was this one:

 So simple, yet so effective!

Adult Challenge of the week:  "Ask your child 'What do you think....'" questions!

Hindsight Tip:  as noted above--pre-prep any items that need to be stretched to create tension so that they make a note.

Related Apps: Sound Uncovered by Exploratorium (Free, iPad only)