Hello again folks,
This week we are looking at, or, in fact, mostly listening to sound.
This video explores the fact that sound is a vibration. You can feel this for yourself if you gently put your fingers on your throat while singing or humming loudly. Again you can feel the vibration on the string if you build yourself some cup and string telephones. Have a go at some of the other experiments suggested too.
Although the vibration travels down the string it is amplified, or made louder by the cups on the end. This is how the clucking cup (as seen in my Birds and the Bees blog post) works. You can also use this to build yourself a speaker for your phone or tablet that doesn't need any electricity.
Musical instruments all rely on something vibrating. Have a go at building yourself a tongue depresser/lolly stick harmonica or a straw oboe. The straw oboe instructions are by Dave Ansell who made our knee surgery exhibit. See if you can work out what it is that is vibrating in these musical instruments.
Generally speaking the bigger/heavier the thing is that is vibrating the lower the sound. Think of the sounds made by descant and treble recorders, or violins and cellos. Try filling some identical glass bottles or jars with different amounts of water and hitting them. Which container produces the lower note? Now try blowing over the top (this is easier with a bottle) and listen to the sound. Which is lower now? Can you work out what is happening? You can also try producing a note by running a slightly wetted finger round the rim of a glass of water. Again you can change the note by changing the amount of water Or the size of the glass. Can you play a tune?
This experiment which uses some string and a metal coat hanger is one of my favourites. You really don't expect what you can hear. It will also work with metal spoons if you can't find any metal coat hangers. This cup and metal slinky combination is supposed to sound like a light sabre.
As well as optical illusions eg Escher's staircase that seems to be endlessly ascending or descending, auditory illusions can also be created. These Shepard Tones, named after their creator sound like they are getting higher and higher pitched even though they are not.
The Let's Get Digital activities in this Oxford Sparks resource for KS4 explore how we convert analogue sounds, as created by singers, musical instruments etc are converted into files eg MP3 files that can be stored or transmitted digitally.
For A level students this explanation of harmonics and standing waves explains some of the maths behind the standing waves that you can create with an electric toothbrush and some dental floss. Although the experiment is fun to carry out whatever your age.
And finally ...
Absolutely nothing to do with sound or kid's activities at all, but here are two new kittens that joined our household this week!