WEB EXCLUSIVE

Blast from the Vast

What sounds do you think of when you see a photo of a sperm whale? Do you associate these marine mammals with a series of clicks louder than a jet engine on takeoff? Scientists are investigating those sounds to learn more about the physics of their production and their role in the animals' survival. Within the sperm whale's elongated head, lies a living architecture of body parts that create, reflect, color, and focus sounds. Emerging from the animal, the clicks become highly focused waves loud enough to temporarily deafen a human!

By Michael DiSpezio|Thursday, December 04, 2003

Reflecting Surface

As you learned, structures within a sperm whale's head affect the behavior of sound waves. Some materials reflect sound, while others absorb it. Still others, such as the liquid within the sperm whales, are good transmitters of these waves.  In this activity, you'll observe firsthand how various materials reflect and absorb sound.

Kitchen counter timer (wind-up type)

Long cardboard tube (insert in wrapping paper roll)

Variety of materials such as wood, paper, acoustic tiles, fabrica, soft foam, filled plastic bag

CAUTION: Never place any object into the ear.

1. With your instructor, review safety techniques when placing objects near the outer ear.

2. Working in teams of two, identify a desktop or floor space that aligns with a wall.

3. Wind up the kitchen timer. Place it several inches from the wall.

4. Wrap your hand around one end of the cardboard tube with your thumb and index finger encircling the tube edge, forming a soft cushion.

5. Place this “cushioned” tube end next to your outer ear.

6. Position the free end of the tube so that it points to the wall as shown. Make sure that the end of the tube is several inches from the wall.

7. Listen to the clicks made by the kitchen timer.

8. Position a piece of wood against the wall at the point where the sound is reflected off the wall and into the cardboard tube. Listen to the clicking and describe any change in the sound.

9. Replace the wood with other materials. Record how each material affects the sound.

Sponsored by:

www.plastics.org


Questions

1. Describe the path of the sound from timer to ear. (Sound travels from timer to material, bounces off the surface to the tube and travels through tube to the ear.)

2. Which materials were the best reflectors of sound? Which materials were the poorest reflectors? (Answers will vary.)

3. Where did the “absorbed” sound energy go? (The energy was transferred from the sound waves in air, to vibrations in the material itself.)

Seeing Stereo

Check out the stereoscopic image at the bottom of page 54. Pretty neat, eh? It looks even more fantastic when the image pair "pops" into three dimensions. Although the cross-eyed technique is described for viewing this image, many people will have difficulty using this viewing strategy. Here's a more effective way to see the 3D effect. Roll two tubes of paper. Use your hands to form a protective "eyecup" at the end of each tube. Hold the tubes like binoculars and bring them to your eyes. Position the open end of each 3 to 4 inches above each photograph. Make sure to hold your viewer so that only one image can be seen through each tube. Once that happens, your brain will do the rest. The separate images will appear to drift together, fuse and produce the 3D effect.

Solid Sound

Explore the way sound travels through solids by placing your ear on a desktop. Gently tap your finger on the surface. Can you hear the sound? Lift your ear while you continue tapping. Compare the sound of tapping that has traveled through the desktop (solid) and through the air (gas). Which material is a better transmitter of sound? (Solid.) Develop a strategy for inquiry to compare distances traveled by tapping sound through air and through the desktop.

Shaping Your Voice

Singers know how to shape (or color) the texture of their voice. They can "place" the voice up in the nasal cavity and get a thin sound. In contrast, they “place” it farther back in the throat and produce a booming sound. Try coloring your voice to produce different sounds. Can you feel the “center” of the voice shifts its location? Which voices are pleasant to listen to? Which ones are offensive?

Sponsored by:

www.plastics.org

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