*+Unit+Content

The purpose of this section is to help the teacher review the content that will provide the foundation for the learning experience.
 * Introduction **

The world is full of numerous sounds, serving a variety of purposes and producing many different effects. Sounds can communicate, warn of danger, entertain, and inform. They can also please or annoy. Vibration causes sound. Sound is a form of energy that moves in waves through all kinds of materials to reach our ears. The ears of all animals, including humans, are designed to catch sound waves in certain ways. When we need to, we can make sounds higher, lower, louder, or softer. Musical instruments make sounds, and some of them are shaped to create or modify certain kinds of sounds. __Scientific inquiry__: the steps that scientists follow when investigating problems in order to form accurate conclusions
 * __Lesson 1: Sounds Good__ **
 * __Hypothesis__: a guess that you make based on information you have observed or gathered
 * __Investigation__: exploring a problem or question by building a model or conducting an experiment
 * __Conclusion__: the best answer to a question based on the data that have been gathered.

Check out [|Sound is Energy] and [|Brainpop] for more information. __Lesson 2: What Makes Sound?__ ** All sounds have one thing in common: each is produced by the vibrations of an object. For something to make a sound, all or part of it has to vibrate. Vibrations are created by actions such as striking, rubbing, plucking, and blowing. For example, hitting a drum or plucking a harp string causes vibrations that produce sounds. Talking and singing are sounds made by blowing air through the larynx, or voice box. It is located in the throat just below the jaw and it has two vocal cords that stretch across the air passage. These cords are relaxed until the person speaks. Then muscles draw them together and air passes the vocal cords, causing the cords to vibrate. People have different voices because the shape and tension of the vocal cords determine the pitch of a voice. The shape of the throat, nose, and mouth also contribute to the quality of a person’s voice. Electrical, mechanical, solar, wind, chemical energy: all these energy forms can cause objects to vibrate. People have found many ways to harness these energy forms for many purposes, including the productions of sound. Electricity is produced by a flow of electrons—and electrical current—along a circuit, or closed path. An electrical circuit consists of a source of electrical energy, such as a battery or generator; an output device, such as a bell; and a wire that connects the power source and the device. __Vibrations__: rapid or slow movements back and forth __Lesson 3: How Do Sound Waves Travel?__ ** Sound waves don’t only radiate from a spot in one flat concentric circle. Sound waves move in all directions from their source. To create a complete picture of how they travel, imagine waves travelling out not on one flat plane, but in concentric radiating spheres. Because the surface area of a sphere increases with its distance from the sphere’s centre, the same amount of sound energy becomes dispersed over a larger area as the sound travels from its source. This spreading out of energy causes the sound pressure to decrease with the distance travelled, and less sound energy strikes the eardrum. In the 17th century, a British scientist named Robert Boyle rang a bell inside a jar that had no air in it. He discovered that the bell could not be heard. Why not? Because sound waves must travel through some medium, such as air, metal, water, or wood. The vibrations of sound cause a chain reaction of collisions of air molecules, transporting the sound to our ears. The molecules in liquids and solids are even closer together than the molecules in air, so vibrations usually move more quickly through liquids and solids than they do through air.
 * __Vocal Chords:__ either of two pairs of folds or membranes in either the larynx- air from the lungs hitting the edges of the lower pair produces sound
 * Visit this website for some more [|Background Information for Sound].
 * ** Book: **** Hearing Sounds ** (Science for Fun) by Gary Gibson (Copper Beach Books, 1995)

More about Sound Waves at: · [] · [] · [] · [] __Lesson 4: How Do Your Ears Catch Sound Waves?__ ** Sirens, air conditioners, barking dogs, conversations—sound of all kinds reach us from every direction. Our curved, fleshy outer ears, the auricles, catch sound waves and funnel them into our ear canals. From there, the waves travel down 2.5cm ear canals to the eardrums. These tiny drum-like structures, just 10 mm in diameter, start vibrating and transmit the vibrations to the bones of the middle ear and to the spiral cochlea of the inner ear, which amplify and convert sound to nerve signals that travel to the brain. Having two ears enables us to detect the source of a particular sound in three dimensional space, from a 180-degree semicircle in front of our bodies and from 180 degrees behind. This also enables us to determine the source of a sound because sounds from one side or the other reach the closer ear a fraction of a second before the other. The difference is not apparent to the ear, but the brain, which interprets the information, can detect the direction of the source. People can lose some of their hearing due to an infection, accident, or old age. Most people with hearing loss use a transistor-powered aid. It amplifies sound waves directly into the ear. Another kind of hearing aid works by sending vibrations through the bony part of the head directly behind the ear to the auditory nerves.
 * __Eardrum:__ Thin membrane that stretches across the middle ear and vibrates when sound waves strike it
 * __Middle ear:__ A cavity, between the eardrum and inner ear, that contains three bones that transmit sound
 * __Inner ear:__ The cavity behind the three bones of the middle ear

More information about our ears: · [] · [] · [] · [] __Lesson 5: What Makes Sounds Soft or Loud, High or Loud?__ ** What causes extremes of sound and all the degrees of softness and loudness in between? Simply put, more energy produces a louder sound. Whispering to a friend takes a lot less energy than yelling to that friend. The difference in energy creates different kinds of sound waves. When you whisper, the vibrations move particles of air only slightly from their normal positions, producing a wave of air pressure along the sound wave path that is only slightly greater or less than normal. When you shout, you move the particles farther, producing waves in which the air much more compressed or rarefied. The term amplitude is used to describe the greatest compression or rarefaction of the air along the path of the sound wave. More energy generates a sound wave with a higher amplitude. The higher amplitude produces a louder perceived sound. Loud sounds travel greater distances than soft sounds because a higher-amplitude wave takes a longer time (and distance) to decrease to zero than a lower-amplitude wave does. Sounds can also be high-pitched, making a high sound like a violin, or low-pitched making a low sound like the rumble of thunder. What creates the difference in pitch? The faster an object vibrates the more sound waves it produces every second. For this reason, we say that a fast-vibrating object has a high frequency, or a high number of vibrations per second. The string for the highest notes on a violin, for example, vibrates quickly. The strong for the violin’s lowest note vibrates slowly. The length, thickness, and tension of the strings also contribute to the differences in pitch. The high-pitched strings are thin, short, and under a lot of tension; the low-pitched strings are thick, long, and under low tension.

• __Volume:__ The loudness or softness of a sound • __Pitch:__ How high or low a sound is • __Cycle__: One peak to the next peak of a sound wave

Watch these 2 videos for more information: · [] · []

Websites: · Loudness: [] · Pitch: [] · The Violin: [] __Lesson 6: Is Sound Used All Around Us?__ ** We hear sounds around us all day, but probably don’t realize how many sounds we hear. The main purpose for sound is for communication, but communication is more than talking. Alarm clocks wake us, horns tell us when the school bus arrives, a ringing telephone means someone wants to talk to us, vehicle noise tells us traffic is moving past, music entertains us, and so on. Breaking down the day by tracking the sounds we hear forces us to realize the importance of sound, and what our life might be without it.

· Book: Kaner, Etta. // Sound Science //. Reading MA: Addison-Wesley, 1991. Explores the nature of sound through experiments, riddles, interesting facts, puzzles and games. · Video: [|Name that Sound]