Sound Travels How sound travels is explained and demonstrated using a spoon and some string to get the vibrations, then sound, to the students ears.

Transcription

1 Sound Travels How sound travels is explained and demonstrated using a spoon and some string to get the vibrations, then sound, to the students ears. Grade Level Used This activity was done with 4 th graders. Duration (Prep/Activity): 15 min/30 min Objectives Materials (per student) -Be able to explain what sound is and how - 2-ft. piece of string or yarn sound travels (propagates) - a rubber band -Be able to explain how the human ear - a spoon works - a worksheet and pencil - a Slinky (one per class) - some larger spoons, mixer beaters, knives, forks, etc. New Mexico Science Standards Strand II: Content of Science, Standard I: Physical Science K-4 Benchmark II: Know that energy is needed to get things done and that energy has different forms. 5-8 Benchmark II: Explain the physical processes involved in the transfer, change, and conservation of energy. Preparations 1. Collect all of the materials for the hands-on experiment. 2. Explain what a sound wave (compression wave) is. Demonstrate this wave using the Slinky. 3. Demonstrate how sound travels with your voice. Explain what is vibrating and what a sound wave is. 4. Talk about how sound can travel in something that has matter (like air, water, etc.), but not in the absence of matter a vacuum like outer space. In space there is nothing to compress. 5. Explain how the ear works. Show pictures of the parts of an ear (see Teacher Background Information). Procedure Focus Question: How does sound travel? 1. Attach the rubber band to the spoon handle. 2. Thread the rubber band onto the string. Move it to the middle of the string. 3. Wrap each end of the string around the ends of your index fingers one on each hand. 4. Gently put your index fingers into your ears. 5. Move back and forth by a table, chair or counter to swing the spoon and gently hit the table, chair or counter with it. 6. Describe what you hear. 7. Have students complete the worksheet (attached). Discuss the answers. 1

2 Follow-up Questions 1. A worksheet with questions follows in the Pictures/Graphs/Additional Information section. Teacher Background Information How an Ear Works The ear is one of the most complicated and delicate measurement instruments of the human body. It can detect sound and send a signal to the brain. It also helps us keep our balance. It is surrounded by the hardest bones we have. The ear is made up of three regions the outer ear, the middle ear and the inner ear. See Picture 1. Picture 1. The Human Ear Starting with the outer ear, Picture 2, you can see that it is designed to collect sound waves. Sounds are collected by the auricle and focused onto the little protrusion on the front of the ear. Once concentrated, this little protrusion directs the sound waves into the external auditory canal or ear canal. It all works like a funnel for sound. The compression waves or sound waves enter the ear canal and are channeled to the eardrum. This is a membrane that vibrates like the head of a drum. 2

3 Picture 2. Outer Ear The middle ear has three bones called the hammer, the anvil and the stirrup. Each one looks like its name. The hammer touches the inside of the eardrum, the anvil touches the hammer and stirrup, and the stirrup touches the inner ear. These bones vibrate to amplify and pass the sound from the outer ear (eardrum) to the inner ear. The middle ear is also where the Eustachian tube is located. It is connected to the back of your throat and is usually collapsed. When you change altitude quickly or the pressure of the air around you changes, your ears feel plugged up, so you yawn. This opens the Eustachian tubes and allows the pressure to equalize on both sides of your eardrum. 3

4 Picture 3. Middle Ear The inner ear is where the sound (vibrations through the hammer, anvil and stirrup) is taken from the oval window (membrane) which vibrates and creates waves in the fluid of the cochlea, through the inner ear, and is translated into an electrical signal. This signal is sent to the brain and compared to all of the stored sounds you have heard before. All of this happens in less than a second. The brain either recognizes the sound or records a new sound and what makes it. Picture 4. Inner Ear 4

5 These pictures of the human ear are from The World Book Encyclopedia, Sound Waves If you drop a pebble into a still pond, you will see a series of waves travel outward from the point where the pebble struck the surface. Sound also travels in waves as it moves through the air or some other medium (substance/matter). The waves are produced by a vibrating object. As a vibrating object moves outward, it compresses the surrounding medium, producing a region of compression. As the vibrating object then moves inward, the medium expands into the space formerly occupied by the object. This is a region of expansion. As the object continues to move outward and inward, a series of compressions and expansions travels away from the object. Sound waves consist of these regions of compression and expansion. Keywords Outer Ear Eardrum Middle Ear Inner Ear Compression Ear Canal Membrane Hammer, Anvil and Stirrup Sound waves Expansion Expected Results The students should be able to hear what sounds like a church bell ringing in their ears. They should also be able to feel the vibration in the string. 5

6 Pictures/Graphs/Additional Information Sound Travels Worksheet For this experiment, you will need a string, a spoon, and a rubber band. Procedure: 1. Attach the rubber band to the spoon handle. 2. Thread the rubber band onto the string. Move it to the middle of the string. 3. Wrap each end of the string around the ends of your index fingers one on each hand. 4. Gently put your index fingers into your ears. 5. Move back and forth by a table, chair or counter to swing the spoon and gently hit the table, chair or counter with it. 6. Describe what you hear. Draw the experimental set up here: Questions 1. What parts of the experimental equipment vibrated? Spoon Rubber band String Fingers Ear Canal Ear Drum 2. Where was the vibration turned into sound waves? 3. Where were the sound waves turned into electrical signals? 4. Describe sound waves 5. Will sound waves travel in a vacuum (space)? 6