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SOUND
Introduction
Physics of Sound
Characteristics of sound Human perception of sound
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INTRODUCTION
What is sound ?
Sound is
A form of energy made by vibrations.
When an object vibrates it causes the air particlesaround it to move.
These particles bump into particles close to themand this continues until they run out of energy.
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INTRODUCTION
How does sound travel ?
Sound travels in forms of waves:
Longitudinal waves
Transverse waves
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SOUND NEEDS MEDIUM
GasesMost of the soundswe hear travel
through gases, suchas air.
Sound waves travelslowly through the
air.
For example: Soundfrom a bell, a horn,or an alarm clock
travels through theair.
LiquidsSome sounds thatwe hear travel
through water.
Sound waves travela faster through
water than throughthe air.
Sonar is the way to
use sounds to locateobjects underwater.
What animals usesonar?
SolidsSome sounds thatwe hear travelthrough solids.
Sound waves travelvery fast throughsolids.
For example: Whenyou hit a drum, itvibrates, then thesound travelsthrough the air, toyour ears.
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PHYSICS OF SOUND
Medium velocity m/sec
air (20 C) 343
air (0 C) 331
water (25 C) 1493sea water 1533
diamond 12000
iron 5130
copper 3560
glass 5640
SPEED OF SOUND IN VARIOUS MEDIUMS :
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Longitudinal Wave
wave particles vibrate back and forth along thepath such that the wave travels.
Also called Compressional Wave
INTRODUCTION
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Transverse waveswave particles vibrate in an up-and-down motion.
INTRODUCTION
Crests Highest part of a wave
Troughs The low points of the wave
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PHYSICS OF SOUND
WAVELENGTH :
THE MINIMUM DISTANCE IN WHICH SOUND WAVE REPEATS ITSELF IS
CALLED WAVELENGTH.
OR
THE DISTANCE BETWEEN THE TWO CONSECUTIVE CREST OR TROUGHS ISCALLED WAVELENGTH.
WAVELENGTH
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PHYSICS OF SOUND
AMPLITUIDE :
THE MAXIMUM DISPLACEMENT OF THE PARTICLE OF THE MEDIUM FROM
THEIR ORIGINAL UNDISTURBED POSITIONS, WHEN THE WAVE PASSESTHROUGH THE MEDIUM, IS CALLED AMPLITUIDE OF THE WAVE.
AMPLITUIDE
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PHYSICS OF SOUND
TIME PERIOD :
THE TIME REQUIRED TO PRODUCE ONE COMPLETE WAVE OR CYCLE.
OR
TIME TAKEN TO COMPLETE ONE COMPLETE VIBERATION
TIME PERIOD
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PHYSICS OF SOUND
FREQUENCY :
THE NUMBER OF COMPLETE WAVES PRODUCED IN ONE SECOND.
OR
NUMBER OF VBERATIONS PER SECOND.
Unit is Hertz (Hz)
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PHYSICS OF SOUND
VELOCITY OF WAVE :
THE DISTANCE TRAVELED BY THE WAVE IN ONE SECOND
VELOCITY = DISTANCE TRAVELED
TIME TAKEN
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PROPOGATION OF SOUND IN SPACE
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CHARACTERISTICS OF SOUND
LOUDNESS :
IT IS THE MEASURE OF SOUND ENERGY REACHING THE EAR PER SECOND.
LOUDNESS DEPENDS UPON THE AMPLITUIDE OF SOUND WAVE.
IT IS MEASURED IN DECIBLE (Db)
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SOUND
Decibel scale
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CHARACTERISTICS OF SOUND
PITCH:IT IS THAT PROPERTY OF SOUND BY WHICH WE CAN
DISTINGUSH BETWEEN DIFFERENT SOUNDS OF THE
SAME LOUDNESS.
IT DEPENDS UPON THE FREQUENCY OF VIBERATION.
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CHARACTERISTICS OF SOUND
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HUMAN EAR
Sound Waves
Sound waves are sent.
The outer ear catches the sound waves.
The middle ear takes the sound waves and vibrates the
eardrum.
The inner ear sends the messages to the brain.
Middle Ear
Inner Ear
Outer Ear
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HUMAN EAR
RANGE OF HEARING IS 20 TO 20,000 Hz.
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SOUND
ULTRASOUND
- sound waves with frequencies above the
normal human range of hearing.Sounds in the range from 20-100kHz
INFRASOUND
- sounds with frequencies below the
normal human range of hearing.
Sounds in the 20-200 Hz range
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HEARING RANGE OF ANIMALS