Moving sound source and its relation to the doppler effect.

1. DOPPLER EFFECT
AND
SONIC BOOM
TEACHER: MS. KATHLEEN BOOTH
SUBJECT: PHYSICS
PRESENTED BY: SANGANAK KASARE

2. SHELDON COOPER AND DOPPLER EFFECT

3. HISTORY OF DOPPLER EFFECT
• In 1984 an Australian Physicist and mathematician, JC Doppler
studied the behaviour of waves as the source, receiver or both are
moving.
• He proposed as the source is moving the waves at the front have a
higher frequency compared to the source being stationary.
• Also the waves trilling behind the source have a lower frequency
compared to the source being stationary.
• The variation in frequencies is noticed by human ears as the change
in pitch as the source moves.

4. DOPPELR EFFECT
• All waves travel outwards from the source (propagate).
• Stationary sources have waves moving outwards in a circular
pattern.
• Moving source: waves ahead of the source are bunched closer.
waves trailing behind the source are spread out.
• This is heard as a: high pitched sound at the front of the source and a
distant drop in pitch as the moving source passes by.

5. MOVING SOURCE
APPROACHING A
STATIONARY
RECEIVER
The Doppler Effect for a person
throwing a ball at constant velocity
every second and traveling at 1 m.s-1
towards the wall.

6. CALCULATING THE OBSERVED FREQUENCY
• f- frequency observed
• f0- frequency emitted by the source
• c- is the velocity of waves in the
medium
• Vr- is the velocity of the receiver
relative to the medium.
• Vs- is the velocity of the source
relative to the medium

7. SOURCE MOVING AT THE SPEED OF SOUND
• The receiver in the front of the
source will not receive any
sound as all the sound waves
are bunched at the source.
f =
c + 0
c - c
*f0( )
=
c * f0
0
= undefined

8. SOURCE MOVING FASTER THEN THE SPEED OF SOUND
• The receiver in the front of the
source will not receive any
sound waves As the waves are
slower then the source and are
trailing behind the source.
f =
c + 0
c - 2c
*f0( )
=
c * f0
-c
= Negative frequency

9. SOURCE MOVING FASTER THEN THE SPEED OF SOUND
• The receiver behind the source will
hear the sound waves emitted from
the source.
• This source radiates 2 waves: a
pressure wave (Mach wave) and
sound wave.
• These waves combine to create the
shockwaves (sonic boom).
• The intensity of the boom increases
as the speed of the source
increases.

10. Mark waves
Aircraft moving faster then the speed
of sound and creating 2 pressure
waves; at the head (point of pressure
rise) and the tail (point of sudden drop
in pressure).

11. BIBLIOGRAPHY
• "What HappensWhen an Aircraft Breaks the Sound Barrier?" Scientific Americans.
Scientific American, a Division of Nature America, Inc., 11 Mar. 2002.Web. 5 Oct. 2015.
<http://www.scientificamerican.com/article/what-happens-when-an-airc/>.
• Kaouri, Katerina. "The Sonic Boom Problem." YouTube.YouTube, 10 Feb. 2015. Web. 05
Oct. 2015. <https://www.youtube.com/watch?v=JO4_VHM69oI>.
• "6.3The Doppler Effect." Physics Uconn.Web. 5 Oct. 2015.
<http://www.phys.uconn.edu/~gibson/Notes/Section6_3/Sec6_3.htm>.
• "Doppler Effect." The for Sound. Hyperphysic. Web. 05 Oct. 2015.
<http://hyperphysics.phy-astr.gsu.edu/hbase/sound/dopp.html>.
• "Breaking the Sound Barrier with an Aircraft." The Sound. Hyperphysics. Web.
<http://hyperphysics.phy-astr.gsu.edu/hbase/sound/soubar.html>.
• UNSW. "The Doppler Effect - A Multimedia Presentation from Physclips." The Doppler
Effect - A Multimedia Presentation from Physclips. School of Physics – UNSW. Web. 05
Oct. 2015. <http://www.animations.physics.unsw.edu.au/waves-sound/Doppler/>.