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Sound Waves

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by

Katie Fadus

on 21 February 2014

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Transcript of Sound Waves

How does the human ear function?
What sound/loudness range is safe for the human ear?
What type of wave is a sound wave?
The speed of sound in different media, such as sound travels quickly in air, faster through water and even faster through solids. On top of that the speed of sound can be manipulated through the temperature. For example, the cooler the medium is the slower the sound travels and the hotter the medium the quicker the sound travels throughout it.
The softest sounds a human can hear are 0 dB, and the highest sounds a human can hear are 120 dB. Any decibel level higher than 120 dB is painful to hear. However, even short exposures of painful sounds can result in hearing loss. So if you are near a loud speaker then simply double the distance between you and the speaker which then reduces the sound's intensity to one-fourth of what you heard when near the loud speaker. This can help to prevent hearing loss and maintain safe hearing range for yourself.
Loudness is a measure of how well a sound can be heard, for example the harder you hit a drum the more energy is transferred so the air particles vibrate father from their resting position. Amplitude is the largest distance of the wave particles from the rest position.
Loudness and Amplitude, how are they related?
The Speed of Sound
For starters, pitch is how high or low a sound seems to be. While as frequency is just the number of crests or troughs given in an amount of time. So if a sound has a high frequency then the pitch is high, same for if a sound has a low frequency then the pitch is low.
Pitch and Frequency, how are they related?
In able to hear sound, first your outer ear collects the sound waves. These vibrations then travel to your middle ear. A very small organ then increases the size of the the vibrations. Then they are picked up by the organs in your inner ear. Your inner ear then changes the vibrations into electrical signals that your brain interprets as sound.
A sound wave is a longitudinal wave, with the particles moving parallel to the direction of the wave motion. In the longitudinal wave there are compressions and rarefactions, that are created when energy is being transferred throughout the wave.
Sound Waves
For a sound wave to move it is required to have a medium; a substance through which a wave can travel such as a solid, liquid or gas; because sound waves require a medium they are also classified as mechanical waves.
How does a wave move?
A perfect representation of sound waves would be a guitar because when you pluck the strings they vibrate as well as the air molecules around creating a pressure wave. In areas of high pressure that is a compression and in areas of low pressure that is a rarefaction.
Sound Waves
A decibel level is the most common unit used to express loudness. The softest sounds a human ear can hear 0 dB, sounds that are 120 dB or higher can be painful to hear.
Common Sounds with their Decibel level
By Katie Fadus
Which animals can hear these frequencies?
Doppler Effect
Oscilloscope
Echoes and How Absorption Factors into Reflected Sound Waves
Echolocation/Sonar Technology
Sonic Boom
Interference in Sound Waves and How it Helps Create Standing Waves
Resonance in Relation to Sound/Music
Sound Quality vs. Noise
Three Types of Instruments
The apparent change in the frequency of a sound caused by the motion of either the listener or the source of the sound.
For example, the person in front of a honking car hears a higher pitch because the car is facing their direction. While as for someone behind the honking car they hear a lower frequency because the waves are having to move in the opposite direction to reach them.
The larger the amplitude the larger the sound and the smaller the amplitude the smaller the sound. Loudness and amplitude work hand in hand with each other.
Humans hearing range is between 20 Hz and 20,000 Hz. Sounds that have too high of a frequency for humans are called ultrasonic which is above 20,000 Hz. If the sound is too low of a frequency for humans it is called infrasonic which is below 20 Hz.
An oscilloscope is a graph representation of waves. Amplitude, frequency, pitch and loudness can all be deciphered from these graphs. It shows the sound as if it were a transverse wave so that it is easier to read and interpret.
Reflection is the bouncing back of a wave after hitting a surface, otherwise known as an echo. Sound waves are reflected best when bouncing back off of a hard, smooth surface. Take an auditorium for example, sound waves are absorbed into the wall so there is no echo while you are enjoying a band performance.
Echolocation is the use of reflected sound waves to locate something. Bats, dolphins and birds use this technique to hunt for food and locate other objects in their paths. They can calculate how far away something is based on how long it takes for the echo to get back to their ears. As for sonar technology, we use ultrasonic waves that give us information to avoid icebergs and even map the ocean floor.
A sonic boom is an explosive sound heard when a shock wave reaches your ears. They can be so loud that they damage your ears, break windows near by, and even shake the ground like an earthquake. A sonic boom is created when the sound waves combine by a constructive interference. You hear the shock wave when it reaches you, not when the jet breaks the sound barrier.
Resonance occur when a vibrating object causes a second object to vibrate at one of its resonant frequencies. For example, a wind instrument the vibrations are made by blowing into the mouth piece making a sound which is then amplified when it forms a standing wave in the instrument.
Examples:
- Flute
-Guitar
-Violin
-Marimba
-Piano
-Harp
These are just a few examples, but there are many more.
Sound quality is the resulting interference of several pitches. Each instrument has it own unique sound quality which explains why when two instrument play the same note, you can tell one from the other. Each note on an instrument is created from the several different pitches : the fundamental and several overtones.
String Instruments:
make sound when the strings are plucked or bowed. For example, a banjo, violin, and guitar.
Wind Instruments:
make sound when a vibration occurs at one end of its air column. They are then divided into two groups of woodwinds and brass. A brass players buzz their lips to vibrate the air, such as a trumpet, or tuba. A woodwind instrument has a reed and that vibrates it for them, for instance a clarinet or saxophone.
Percussion Instruments:
make sound when struck, instruments of different sizes are used to get different pitches. For example, drums, bells and cymbals.
Noise is sound that is a mix of different frequencies, which can be displeasing to the ear. While as sound quality is combines like frequencies from different instrument creating that harmony in the sound.
A standing wave is a pattern of vibration that looks like the wave is standing still because the both the waves and reflected waves have the same frequency going through the string.
Interference in sound waves helps to create a multitude of things, such as fundamental frequencies, and resonant frequencies which then create standing waves. A fundamental frequency is just several standing waves of different frequencies at the same time. The frequencies at which standing waves are created are called resonant frequencies.
Bibliography
~Holt Science & Technology: Georgia, Physical Science Copyright 2008 (this was my only source for this project)
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