# Hands-on science: (no lab required).

After reading "Night Fright" (p. 14), try out this activity to learn how sound waves help aye-ayes locate food.

PREDICT

Suppose you were to tap on a large hollow object and on a similar, but smaller hollow object. How would the sounds compare?

MATERIALS

2 liter (67 fluid ounce) soda bottle, empty and with the top third cut off * 3 sheets of newspaper * wooden pencil * 591 milliliter (20 fluid ounce) soda bottle, empty and with the top third cut off

PROCEDURE

1 Crumple 3 sheets of newspaper into a ball.

2 Place the crumpled newspaper inside the large soda bottle.

3 Hold your ear close to the large, paper-filled bottle. Tap the end of your pencil on the side of the bottle. Note the sound that you hear.

4 Remove the newspaper from the large soda bottle.

5 Again, tap the end of your pencil on the side of the soda bottle. Note the sound that you hear now that the soda bottle is empty: Does it have a higher pitch, or a lower pitch than when the bottle was filled with newspaper?

6 Tap your pencil on the side of the small empty soda bottle. Note the sound that you hear: How does it compare with the sounds you heard when you tapped the larger soda bottle?

CONCLUSIONS

1 Could you hear a difference in sound produced by the large soda bottle when it was full of paper versus when it was empty? Explain.

2 Which empty soda bottle produced the lower-pitch sound when you tapped on it--the large bottle or the small one?

3 Sound waves with a high frequency, or number of vibrations per second, have a high pitch. Which soda bottle had the highest frequency when you tapped on it: the large one when it was full, the large one when it was empty, or the small one when it was empty?

4 Suppose an aye-aye were to tap on a tree branch in search of a meaty meal. If it were hunting for wood-boring insect larvae, what kind of sound would it listen for? Explain your reasoning.

TAKE IT FURTHER

Try the experiment again. This time instead of using soda bottles, use an empty toilet-paper roll and an empty cardboard breadcrumb container. Do you get the same results?

1. You should have heard a difference between the sound produced by the empty versus the paper-filled soda bottle, When you tapped on the paper-filled bottle, the paper absorbed some of the sound waves before the waves bounced back to your ears. That absorption made the echo sound more muffled than the echo from the empty bottle.

2. The large bottle should have produced a lower-pitch sound compared with the small bottle. That's because the frequency of a vibrating sound wave depends on the wavelength of these vibrations. The longer the wavelength, the lower the frequency, meaning a lower pitch. The large bottle could produce a longer wavelength--and lower pitch--than the small bottle.

3. The small, empty bottle should have produced the highest pitch. That's because the small bottle produces sound waves with a shorter wavelength, meaning more vibrations per second, or a higher frequency.

4. An aye-aye would search for a low-pitch sound. This would indicate a large cavity inside the tree trunk--hopefully crawling with insects.