Behavior of Sound (Archi)
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Transcript of Behavior of Sound (Archi)
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BEHAVIOR OF
SOUND-REFLECTION - REFRACTION
-INTERFERENCE - RESONANCE-DOPPLER EFFECT
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REFLECTION OF SOUND
Sound wave bounces whena boundary is met.
A reflection of sound iscalled an echo.
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REFLECTION OF SOUND
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Hard and smooth materials reflectsound better.
Rough and soft materials have greaterability to absorb sound.
REVERBERATIONS multiplereflections
REFLECTION OF SOUND
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REFRACTION OF SOUND
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involves a change in the direction andspeed of waves as they pass from onemedium to another.
Warmer temperature- sound travelsfaster
Colder temperature- sound travelsslower
REFRACTION OF SOUND
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DIFFRACTION
Diffraction of sound is the bendingof sound wave through a small
opening.
Diffraction involves a change indirection of waves as they pass throughan opening or around a barrier in theirpath.
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INTERFERENCE OF SOUND
When two waves meet at a certainpoint.CONSTRUCTIVE INTERFERENCEDESTRUCTIVE INTERFERENCE
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Beats
When 2 tunes of slightly different frequencyare sounded together, fluctuations in theloudness of the combined sound is heard.
Periodic variation in the loudness of sound is
called beats.
Beats are produced due to interference.
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Beats
Constructive interference loud sound
Destructive interference soft sound
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NATURAL FREQUENCY
The frequency or frequencies at which
an object tends to vibrate with when hit,struck, plucked, strummed or somehowdisturbed is known as the naturalfrequency of the object.
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FORCED VIBRATION
The tendency of one object toforce another adjoining or
interconnected object intovibrational motion is referred toas a forced vibration .
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RESONANCE
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Simulation: Sympathetic vibration
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RESONANCE
occurs when two interconnected objectsshare the same vibrational frequency.
When one of the objects is vibrating, itforces the second object into vibrationalmotion.
The result is a large vibration.
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What do you observe in the sound that
you hear when an ambulance passes by?
fire truck train
http://nz.youtube.com/watch?v=imoxDcn2Sgohttp://nz.youtube.com/watch?v=lgKMencd3zEhttp://nz.youtube.com/watch?v=lgKMencd3zEhttp://nz.youtube.com/watch?v=imoxDcn2Sgo -
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DOPPLER EFFECT
Waves formed by stationarysource.
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DOPPLER EFFECT
Waves formed by a moving source.
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DOPPLER EFFECT
HIGHFREQUENCY
LOWFREQUENCY
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DOPPLER EFFECT
Apparent change in thefrequency of soundobserved whenever the
source of waves ismoving with respect toan observer.
It was discovered byHans ChristianDoppler.
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Mathematical Proof
Source is moving away toward thelistener:
f = ___f___1- (v s / v)
Where:f= new frequency
f=original frequency of soundvs = Velocity of sourcev = velocity of sound
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Source moving away from the listener:
f = ___f___1+ (v s / v)
Where:f= new frequency f=original frequency of soundvs = Velocity of sourcev = velocity of sound
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SHOCK WAVES
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Shock waves
Are produced if the source actually moves atthe same speed as or faster than the waveitself can move.
Produced by an aircraft moving faster thanthe speed of sound.
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Sonic Boom
If a fast aircraft moves above you, you willhear a sonic boom
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Sonic Boom
The result of the piling up of compressionalwavefronts .These compressional wavefronts
pile up and interfere to produce a very highpressure zone.
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PROBLEM SOLVING
What is the speed of sound when thetemperature is 38 0 C?
Most people can detect frequencies as highas 20 000 Hz. Assuming the speed of soundin air is 345 m/s, determine the wavelength ofthe sound corresponding to this upper rangeof audible hearing.
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On a hot summer day, a pesky little mosquitoproduced its warning sound near your ear.The sound is produced by the beating of its
wings at a rate of about 600 wing beats persecond.a. What is the frequency in Hertz of the soundwave? b. Assuming the sound wave moveswith a velocity of 350 m/s, what is thewavelength of the wave
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Playing middle C on the piano keyboardproduces a sound with a frequency of 256Hz. Assuming the speed of sound in air is 345
m/s, determine the wavelength of the soundcorresponding to the note of middle C.
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Problem-solving
The siren of a police car at rest emits apredominant frequency of 1600 Hz. Whatfrequency will you hear if you are at rest and
the police car moves at 250m/s. a) towardyou b) away from you. If the surrounding airtemperature is 32 deg Celsius?
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