Sound is a pressure wave that travels through air or other media and can be detected by the human ear within a range of 20-20,000 cycles per second. Sound is produced by vibration and travels by pushing adjacent particles, propagating outward from the source. It can travel as longitudinal waves through solids, liquids, and gases, with particles vibrating parallel to the direction of travel. The Doppler effect describes how the observed frequency of sound waves is different for an observer moving relative to its source.

1. PREPARED BY
V.REVATHIAMBIKA
LECTURER IN PHYSICS

2. SOUND
• It is the sensation that is caused by stimulation of the
organs of hearing by vibrations transmitted through the
air or another medium.
• It is transmitted as condensations and rarefactions in the
medium. It is called a pressure wave.
• Human ear can detect only those waves whose
frequency of vibrations are in the range 20 – 20000
cycles/ sec.

6. PRODUCTION OF SOUND
• Sound has great importance in our daily life.
• Sound makes it possible for us to communicate with
one another through speech.
 Musical sound gives us pleasure.
 Radio and Television sound gives us information and
entertainment.
 Horn sound of vehicles alert us.

8. PROPAGATION OF SOUND
• Sound travels through a medium from
the point of generation to the listener.
• Sound waves travel along the to and
fro movement of the vibrating objects
that produce them.
• Example :
Throw a stone into a pool of water.
See the circular waves spread out from
the point of disturbance and travel
outward on the surface of water

9. waves
Electro Magnetic Waves
(transverse waves)
Mechanical Waves
Eg: Light Waves, Infrared,
Ultraviolet, etc.,
Longitudinal Waves Transverse Waves
Eg: Sound Waves Eg: Water Waves

12. DIFFERENCE BETWEEN TRANSVERSE AND
LONGITUDINAL WAVES
TRANSVERSE WAVES LONGITUDINAL WAVES
Particles of the medium vibrate in Particles of the medium vibrate in
a direction which is perpendicular a direction which is parallel to the
to the direction of propagation. direction of propagation.
Crests and troughs are formed Compressions and rarefactions are
formed
Can travel through solids and Can travel through solids , liquid
surfaces of liquid and gases
Example : water waves Example : sound waves

14. • The maximum displacement of a particle
from the mean position
AMPLITUDE(a) • UNIT : metre
• Time taken by a particleof the medium
to complete one vibration
TIME PERIOD(T) • UNIT : second
• The number of vibrations completed by
a particle in one second
FREQUENCY(n) • UNIT : hertz
• Distance moved by a wave during the
time a particle completes one vibration
WAVELENGTH(λ) • UNIT : metre

15. ECHO
• The sound waves produced by us bounce back or reflected from the
forest or mountain or buildings come to our ears as Echo.
• Example :
• The sound uttered by a person may be heard two or three times
after the reflection from an object.
• The sensation of sound persists in our brain for about 1/10th of a
second.
• Echoes may be heard more than once due to successive or multiple
reflections.
• The rolling of thunder is due to the successive reflections of the
sound from a number of reflecting surfaces, such as cloud and land.

16. REFLECTION OF SOUND

17. REVERBERATION

21. APPLICATION OF ULTRASOUND
• Ultra sound scan is currently considered to be
a safe, non-invasive, accurate and cost
effective investigation of the foetus.
• It has progressively become an indispensable
obstetric tool and plays an important role in
the care of every pregnant women.
• Ultra sound sent by transmitter and received
by the detector.

23. SONAR
• It is a device that uses ultrasonic waves to measure
the distance, direction and speed of underwear
objects and depth of the sea, locate under water
hills, submarine, icebergs, sunken ship, etc.,
• ECHO Ranging :
• time interval between transmission and reception of
ultrasound is “t” speed of sound through water is “ v
“ total distance travelled is “ 2d “
2d = v *t
d = v * t /2

25. DOPPLER’S EFFECT
The phenomenon of
the apparent change
in the frequency of
the source due to
relative motion
between the source
and the observer is
called as Doppler’s
Effect.

26. Uses of Doppler effect in sound
• The doppler shift of radar waves are used in
airports to find the height, speed and distance
of approaching aircrafts.
• Bats send out and receive ultrasonic waves
reflected by the prey and obstacles. Bats
detect the location, distance and movement
of the prey by the Doppler Shift.