The Fairy-Land of Science · Lecture VI, part 3 · Part 6: Lecture VI: The voices of nature and how we hear them
18. Notes, noises, and the voices of nature
Goal: Your child can show that faster shaking makes a higher note, tell a musical note from a noise, and explain what makes thunder roll.
You'll need
- A wooden or plastic ruler
- A table edge
- Two or three glass bottles or jars with different amounts of water
- Science notebook and pencils
What's in the book
Pages 140 to 149. Noise is uneven shocks; a note is quick, even shocks, like a stick run along a fence; a notched wheel and two tuning forks show that faster shaking makes a higher note; the brook, the sea, the wind and a glass jar each make their own sounds; how lightning makes thunder; how insects buzz and beetles bore; and the long song of the lark.
The lesson, step by step
Hook question
Drop a handful of dry beans or pebbles into a pan: that's a noise. Hum one note: that's a note.
SayWhat is the difference?
Read page 140.
But if you run a stick very quickly along a paling, you will hear a sound very like a musical note.
The bumps come quickly and evenly, so we hear a note.
Try it: the twanging ruler
Hold the ruler flat on the table with most of it sticking out over the edge. Press the table end down firmly and twang the free end. Now slide it so less sticks out and twang again.
We can also prove by this experiment that the quicker the blows are, the higher the note will be.
SayA short ruler shakes faster, so the note is higher. A long ruler shakes slowly: a low note.
Try it: bottle music
Buckley held a tuning fork over a glass jar while she poured in water, until the jar "answered" with a loud note. Blow gently across the tops of your bottles. Each sings its own note. Add or pour out water and listen to the note change.
Nature's voices
Read page 143.
Why does it sing so sweetly, while the wide deep river makes no noise?
The brook bumps over stones; the waves burst little bubbles of air and drag pebbles down the beach. Read about thunder on page 146: the lightning heats the air so fast it bursts out in sound waves all along its path, and we hear them one after another as a long roll.
What we know now
Sound is slower than Buckley says: it goes about a mile in five seconds. When you see lightning, count the seconds until the thunder; every five seconds is about a mile away.
Buckley says gnats and bees buzz by scraping their wings on their legs. We now know their buzz comes from their wings beating very fast (a bee's, about 200 times a second). Crickets and grasshoppers do make their chirps by scraping.
The sea sound in a shell is mostly the sounds around you, echoing inside the shell.
Tell it back and check
Your child tells back why the short ruler sounds higher. Then ask:
1. What is the difference between a note and a noise?
2. Does faster shaking make a higher or a lower note?
3. Why does thunder rumble on and on?
Listen to a bird
Read page 148.
The next time you are in the country in the spring, spend half an hour listening to him
Buckley means the lark. Any bird will do. Go outside, find a singing bird, and listen as long as your child can manage. Then draw the bird and write down what its song sounded like.
Afterwards
Notice it this week: run a stick along a fence, listen to rain on different surfaces, and count from lightning to thunder in a storm (from indoors).
Tip
If the ruler just thuds, press the table end down harder with your palm. A wooden ruler sticking out about half its length gives a good low twang.
Answers to the book's problems
1. A note is made by quick, regular shocks; a noise by uneven ones. 2. Higher. 3. The lightning makes sound all along its path, miles long, and the sound from the far parts takes longer to reach us, so it arrives as a long roll (echoes from clouds and hills add to it).
Worked out for this site from the scan. If a number in your copy differs, trust the book.