Sound+Waves



> **What are sound waves?** > Sound waves are made by the vibrations of objects moving around. A good example is a guitar string, if you pluck it, it vibrates causing pressure waves (sound waves) to move through the air. When the sound reaches the ear, you hear the sound that the wave made. >

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> **The discovery of sound waves?** > Sound waves were first discovered by Pythagoras of Samos in the early sixth century B.C. he started by observing how the guitar string vibrates, and how when it stops, the sound also stops. By 400 B.C. Archytas of Tarentum a member of the Pythagorean school suggested that sound was made by the striking together of different bodies. By about 350 B.C. Aristotle was showing that the vibrations of a string was shaking the air around it and some of the air that was hit must in turn shake the air next to it, in turn it struck the next and so on. Aristotle also deducted that sound would not be conducted through a vacuum "which is in fact correct".

**The speed of sound** The speed of sound is how fast sound moves in a certain amount of time. The speed of sound varies depending on the temperature of the air. The colder the air the slower the speed of sound will be, the warmer the air the faster. At 68 degrees fahrenheit sound travels through air at the speed of 1130 ft/sec, about a mile per every 5 seconds. also you can measure the distance of lighting by counting the number of seconds between when you see the light and when you hear the sound then divide it by 5. For example if you saw lighting then counted to 20 and then heard thunder, you can determine that the is approximately four miles between you and where the lighting struck.

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> **Guitar String Observations** > Differences and their affects on the sound: >

> Differences that affect pitch >

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 * [[image:http://3.bp.blogspot.com/-rce-TlP3iik/TZ-SkqfH71I/AAAAAAAAAAM/3rvXgbtd8BQ/s320/FatString.png width="320" height="176" align="center" link="@http://3.bp.blogspot.com/-rce-TlP3iik/TZ-SkqfH71I/AAAAAAAAAAM/3rvXgbtd8BQ/s1600/FatString.png"]] ||
 * Fat String ||

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> the pitch of the FAT string was lower.the vibrations for the fat string were slighty slower. The sound of the fat string lasted longer. > when both were PLUCKED fat string sounded, covering the skinny one. >

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 * [[image:http://1.bp.blogspot.com/-LboBeF0-2aM/TZ-SlU5wYgI/AAAAAAAAAAQ/DtG3wx3E1Lc/s320/SkinnyString.png width="320" height="166" align="center" link="@http://1.bp.blogspot.com/-LboBeF0-2aM/TZ-SlU5wYgI/AAAAAAAAAAQ/DtG3wx3E1Lc/s1600/SkinnyString.png"]] ||
 * Skinny String ||

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> The hieght of the mountain indicate tone how loud it was. > The width of each individual mountaiun indicates the pitch > length - > thickness > > type (plastic, metal, ...) > tightness

> sound > **Why does this happen?** > >

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> **Stuff to Add:** > sound is like a wave. its a way in which energy gets from one place to another. > Energy is what makes things move. Energy comes in two forms: kinetic energy and potential energy. >

> <span style="font-family: Arial,Verdana,sans-serif; font-size: 25px;">Sound waves are measured in cycles per second or hertz. It was named after the German scientist Heinrich Hertz<span style="background-attachment: initial; background-clip: initial; background-color: #ffff66; background-image: initial; background-origin: initial; background-position: initial initial; background-repeat: initial initial;"> (insert link to Wikipedia entry on Heinrich Hertz) who lived from 1857-1894. If 100 wave crests pass a given point in one second, we would say it had a wave frequency of 100hz. The actual height of the wave is called amplitude. >

> <span style="font-family: Arial,Verdana,sans-serif; font-size: 25px;">Air is like water and when the guitar string moves back and forth it moves the air creating a wave that travels through space until it reaches our ear drum, which is them interpreted by our brain as sound. >

> <span style="font-family: Arial,Verdana,sans-serif; font-size: 25px;">Sound can not travel through a vacuum because, there are no molecules to carry the sound. >

> <span style="font-family: Arial,Verdana,sans-serif; font-size: 25px;">The speed at which a guitar string vibrates determines the frequency and wavelength of the sound. The faster the //vibrations//, the smaller the amplitude and the higher the hertz, the slower the vibrations, the larger the amplitude and the lower the hertz, >

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> <span style="font-family: Arial,Verdana,sans-serif; font-size: 25px;">Sound waves by themselves we can not hear. > <span style="font-family: Arial,Verdana,sans-serif; font-size: 25px;">Are ears are very important to the way we hear, without them we would not hear sound. >

> <span style="font-family: Arial,Verdana,sans-serif; font-size: 25px;">The first and most obvious part of the ear is the ear flap that is made into sort of a cup that acts like a funnel capturing sound waves and directing them into a tiny tube shaped passage way called meatus. At the end of this we find the membrane which acts as a sort of cover to a drum taught all around. This membrane is usually referred to as the ear drum. >

> <span style="font-family: Arial,Verdana,sans-serif; font-size: 25px;">When sound waves hit the ear drum it forces it too move inward after. it passes the sound wave lets the ear drum pop up again and when the next sound wave hits the ear drum it makes it move inward again. >

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> <span style="font-family: Arial,Verdana,sans-serif; font-size: 25px;">When a sound wave strike the ear drum it causes it to vibrate in the same way that what caused it to vibrate in the first place. For example when you pluck a guitar string is vibrates and your ear drum will vibrate at the same frequency as the guitar string. >

> <span style="font-family: Arial,Verdana,sans-serif; font-size: 25px;">on the other side of our ear drum are the middle ear and the inner ear,where the sound waves are converted into electrical, and chemical energy.the middle ear acts like the safety buffer, and amplifier,quieting loud sounds and making softer sounds louder so that we may here them. It also carries the sound waves on into the inner ear. >

> <span style="font-family: Arial,Verdana,sans-serif; font-size: 25px;">Once inside the inner ear, the vibrations wander through a series of paths and tunnels filled with fluid. As they travel through this maze, they are sorted out by their levels of frequency.next they are detected by tiny hairs which send their own electrical and chemical signals to the brain. >

> <span style="font-family: Arial,Verdana,sans-serif; font-size: 25px;">The loudness of a sound wave is determined by the the amount of energy in the vibration. We can also say that the more the energy, the higher the amplitude and the louder the sound. We measure loudness in a unit called bell, named after Alexander Graham Bell, the inventor of the telephone. Because the bell represents a rather large difference in loudness, we usually use one tenth of the bell (e.g., Decibell, dB). >

> <span style="font-family: Arial,Verdana,sans-serif; font-size: 25px;">The loudness of sounds falls very quickly. You might think that if you move twice as far away from source of the noise that it would sound half as loud. In fact, it would sound one fourth as loud. If you move four times farther away, it will actually sound one sixteenth times less. Eventually, when you move far enough way, you will not hear the sound at all. Put formula >

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> <span style="font-family: Arial,Verdana,sans-serif; font-size: 25px;">If a tree falls in the forest and no one is there to hear it does it make a sound? > <span style="font-family: Arial,Verdana,sans-serif; font-size: 25px;">Yes, because it does create sound waves that will reach you eventually it will be so weak that you don't here it. >

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