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 liter, abbr. l, unit of volume in the metric system, defined since 1964 as equal to 0.001 cubic meters, or 1 cubic decimeter. A cube that has each of its edges equal to 10 centimeters has a volume of 1 liter. The liter is equal to 1.057 liquid quarts, 0. (67 fluid ounce fluid ounce or fluidounce n. Abbr. fl oz, fl. oz. A unit of volume or capacity equal to 8 fluid drams or 29.57 milliliters. ) soda bottle, empty and with the top third cut off * 3 sheets of newspaper * wooden pencil * 591 milliliter milliliter /mil·li·li·ter/ (mL) (-le?ter) one thousandth (10-3) of a liter. mil·li·li·ter n. Abbr. (20 fluid ounce) soda bottle, empty and with the top third cut off PROCEDURE 1 Crumple crum·ple v. crum·pled, crum·pling, crum·ples v.tr. 1. To crush together or press into wrinkles; rumple. 2. To cause to collapse. v.intr. 1. 3 sheets of newspaper into a ball. 2 Place the crumpled crum·ple v. crum·pled, crum·pling, crum·ples v.tr. 1. To crush together or press into wrinkles; rumple. 2. To cause to collapse. v.intr. 1. 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 Larvae, in Roman religion Larvae: see lemures. , 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 See breadcrumbs. container. Do you get the same results? ANSWERS 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 muf·fle 1 tr.v. muf·fled, muf·fling, muf·fles 1. To wrap up, as in a blanket or shawl, for warmth, protection, or secrecy. 2. a. 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 vibrating, v using quivering hand motions made across the client's body for therapeutic purposes. 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. |
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