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If a tree falls down in a forest and no person is around, is it considered sound? Yes, sound exists even if someone is not around to hear it. Sound consists of the vibrations of the surrounding medium. Sound is a form of energy that is produced by things that move in quivering motions called vibrations. Vibrations travel through the air. Sound is used as an important way to communicate and a way to be aware of ones surroundings. There are wide variations of sounds that can he made. Sounds travel all around us in waves. When sound waves reach our ears we hear sounds.
Air can carry several vibrations simultaneously. Vibrations travel in many different directions. Humans can hear a radio playing, a bird singing, a car, an airplane, a friend talking, and other noises at one time. Sounds make the world an interesting place to live.
Objects that vibrate make the air vibrate. When a vibrating material moves outward, it compresses the surrounding air. Air expands and rushes into space occupied by a vibrating object when a vibrating material moves inward. Every vibration that follows causes the air surrounding it to compress and expand.
The compressions made in the air by the vibrations are called condensations. The expansions made by the vibrating object are call rarifactions. The compressions and expansions located near the source of the sound continue to compress and expand the air farther away so the vibrations travel through the air as sound waves.
Sound waves travel through the air from a source as long as the source is vibrating. Sound waves travel along the back and forth action ot the vibrating object, these waves are called compression waves or longitudinal waves. Sound waves are composed of compressed and expanded air that continues to move back and forth in exactly the same direction that the wave is traveling.
An oscilloscope is used by scientists to study sound. Oscilloscopes can show the pattern of sounds waves or the shape of the sound waves, this electronic device is used to observe and measure any oscillation or vibration that can be changed into an electrical voltage. This device shows the vibrations of the voltage which corresponds to the sound waves on a fluorescent screen of a cathode-ray tube.
Sound travels through a medium. the speed at which sound travels depends upon the density of the medium through which the sound waves are traveling and the elasticity of the medium. Dense mediums slow down the speed of sound. Mediums with more elasticity speed up the speed of sound. For example, sound moves faster through steel than through air. Steel is two million times more elastic than air even though it is 6,000 times denser than air. As the temperature changes, the elasticity and density of air changes. therefore, the speed of sound in air changes as a result of the temperature. Sound travels at a slower speed than the speed of light. Sound travels at different speeds depending upon the medium through which it travels. Sound travels at a speed of 1,100 feet per second in air. In water, sound travels at 4,700 feet per second. In brick, sound travels at 11,900 feet per second. Sound travels at 16,400 feet per second in steel. Sound will not travel in a vacuum where there is no substance.
Sound waves enter the human ear and travel down long tubes to the eardrums and other fragile organs that send the vibrations to nerves that go to the brain. There the sounds are interpreted. Sounds which can not be heard by the human ear are below the threshold 01' audibility, the point at which we can hear sounds. the sounds which are loud enough to hurt the can are considered to be above the threshold of hearing. ii someone needs more and more intense sounds to hear, then that person is probably going deaL
Sound waves have different characteristics. Musical sounds have quality and pitch. Pitch is the clement of the sound of a tone or sound determined by the frequency of vibration ot the sound waves entering the ear. Frequency refers to the number of times an object vibrates in a second. the greater the frequency, the higher the pitch. People can hear different ranges of sound frequencies. Dogs and bats can hear sounds humans can not.
Sounds have intensity and levels of loudness. -t he amount of energy that is moving in the sound wave refers to its intensity. Loudness of sound refers to the strength of the sound sensation that is received by the eardrum and then sent onto the brain. I he intensity and loudness of a sound depends upon the distance from the sound source, the amplitude of vibrations, the density of the medium that the sound wave is traveling through. and the area of the vibrating material. As the distance between a human and the sound source increases. then the loudness and intensity of the sound decreases. Sound waves move out from then- sound source in all directions. tn sound waves, the energy flowing spreads out over greater areas and decreases as it travels tanther away worn the sound source.
The distance that a vibrating object moves when it is vibrating is the amplitude of vibration. More energy is needed for an object to produce a large amplitude of vibration. Large amplitudes of vibration coming from a sound source result in louder and more intense sounds. As the density of a medium decreases, then the intensity and loudness of a sound decreases.
A vibrating source's area affects the intensity and loudness of a sound. A ticking clock will sound louder if you place it so that it rests against another object. I his placement of the clock increases the area of vibration and makes the sound louder and more intense.
The pitch of a sound depends upon the number of sound waves passing a certain point in one second. f he frequency of a sound is measured in hertz (Hz). the higher the frequency of a sound, then the more high pitched the sound. I he hearing range for human beings is from 20 to 20,000 Hz.
The Doppler Effect, in relation to sound, is the change that is observed in the frcqucncy' of sound waves because of the motion between the sound source and a listener. the pitch of a train whistle appears to get higher as the train comes closer to a listener, the pitch of the train whistle seems to drop as the train passes the listener and goes farther away. However, the actual pitch of the whistle remains constant. there are more sound vibrations that reach a listener's ear every second as the train comes closer to them. I his happens because the sound waves are closer together. A listener will hear less vibrations when the tram goes past them because the sound waves are stretched farther apart from each other.
A decibel is a unit of sound pressure that is measured by a decibel meter. the decibel scale accommodates a wide range if sounds. A decibel is a unit of measurement used to measure the intensity of sound. A sound intensity of 0 decibels is at the threshold of audibility for the normal ear. Sounds at 10 decibels have an intensity ten times greater than a sound of 0 decibels. A human whisper can be measured at 20 decibels. Ordinary speaking voices have been measured at 60 decibels. Human ears are sensitive to a wide range of sounds. Human ears have low sensitivity to low pitches, the sensitivity of the human car increases as the pitch increases until the pitch reaches 1,000 vibrations per second. I hen the human ear's sensitivity to the sound decreases again.
Humans speak as a result of sound being produced by air columns that are vibrated by membranes. Vocal cords are located on each side of the larynx, the voice box. By fOrcing air past these cords, people make these cords vibrate. Different pitches of sounds are produced by changing the tension on the cords.
Sounds are created by animals in different ways. Many animals have vocal cords and make sounds 1ikc humans do. Some insects make sounds by rubbing their wings together. Buzzing bees and flies make sounds by beating their wings in the air and causing vibrations.
There are musical and noisy sounds. Musical sounds are produced by a vibrating source that generates regular vibrations at regular intcrvals. Skilled musicians can play pleasant musical sounds. Noisy sounds send out irregular vibrations at irregular intervals. A chain saw makes irregular vibrations and creates unpleasant noise.
Musical sounds can relax listeners. Stringed instruments, wind, and percussion instruments can make music. Violins have strings stretched over a resonance box. The tightness of the strings will control the frequency at which it vibrates and the pitch of the sound it makes. Increased tension in the string increases the frequency of sound it makes. Longer strings lower the frequency of the sound made. Musicians control the length of the vibrating strings on their instruments by pressing their fingers on the strings in various places. One end of the string on the instrument is attached to the resonance box and the other end is attached to a peg on the instrument. The musician is able to play a wide range of tones. tones are sounds that are distinct and identifiable by regularity of the vibration or constant pitch that can place it in harmonic relation with other sounds.
Musicians play wind instruments by blowing a stream of air over the opening of a pipe or tube. This stream of air activates the air column inside the pipe or tube to vibrate. The length of the pipe or tube affects the frequency of the vibration of this air column. Pressing valves regulates the length of the column of air created that produces the sounds in wind instruments. Reeds help make the air columns vibrate in inusicai instruments.
Musical instruments like drums, cymbals, gongs, and bells are percussion instruments. These musical instruments are often beaten to make vibrations to generate sounds. When these instruments are played badly, they generate noise, or unpleasant sounds.
Noise can harm humans. Loud and unpleasant sounds can damage your hearing. Noise pollution can cause hearing loss, pain, and stress. Noise is unwanted sounds. Any decibel reading at 85 dBs or above can damage hearing. Noise regulation laws exist to protect workers and should be followed in homes to protect humans, pets, and other wildlife from damage to their physical and social well-being. Builders can use insulated walls and acoustical ceilings to reduce sounds. they can seal cracks located on the inside and outside of buildings to reduce noise from the outside. Special window panes, drapes, carpets, and thicker doors will also keep unwanted sounds out.
Acoustics is the science that studies how to control sound. Theaters are designed to add clarity to useful sounds. Acoustical engineers design buildings and select material to enhance good sounds and reduce noises. Unwanted sounds can be reflected or absorbed by other materials.
The world is full of sound. Every living creature deserves a life hill of good sounds that do not harm them. Noise pollution needs to be reduced for the benefit of every living thing. Sound can be used to enhance and enrich living things. Sound can also warn living things of dangers. Sound is a form of energy that creates an auditory effect that is distinctive and identifiable and can add to the quality of life.
Bibliography
Darling, David. Sounds Interesting. New York: Dillion Press, 1991.
De Pinna, Simon. Sound. Texas:Raintree Steck-Vaughn,l998.
Friedhoffer, Robert. Sound New York: Franklin Watts, 1992.
Hewitt. Susan. Hearing Sounds. New York: Children's Press, 1998.
Lampton, Chrisotpher. Sound. New Jersey: Enslow Publisher. Inc., 1992.
Levine. Shar, and Leslie Johnsione. The Science of Sound and Music. New York: Sterling Publishing Co.. Inc., 2000.
Pringle. Laurence. Hearing. New York: Benchmark Books, 2000.
Walpole, Brenda. Hearing. Texas: Steck-Vaughn.1 997.
Ward, Brain. The Ear and Hearing Ne York: Franklin Watts, 1981.
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