It is composed of waves of
compression and rarefaction in
which the human ear is sensitive
Sound may be described by four perceptual characteristics:
Pitch – refers to the highness or lowness of a sound. It depends upon the
frequency of the sounding object. Higher frequency sounds produce high
pitch while lower frequency sounds produce low pitch.
Loudness – is a physiological sensation that varies from one person to
another. It depends on the sense of hearing, the distance from the source
and the material through which the sound travels.
- description of how high or low
the sound seems to a person
. Loudnesshow loud or soft a sound is
perceived to be.
Sound Waves – is a longitudinal wave
created by vibrating solids, liquids or gases
and capable of producing a sensation in our
auditory system. It can travel through a
medium from one location to another. It
travels at a speed of 331m/s in air at sea
level when the temperature is 0 degree.
Just like all longitudinal
Waves possess a velocity,
phase, period, and amplitude.
Sound waves also reflect,
refract, diffract, and interfere.
2. LOUDNESS or intensity
-description of how high or low
the sound seems to a person
-determined mainly by the
amplitude of the sound
a. Decibel (dB)- unit used to
measure sound intensity or
Speed of Sound
1. Type of medium
-travels better through liquids and solids
and gas can’t travel through a vacuum.
2. Temperature of medium
-travels faster at higher temperature.
-sound moves well through dense
-sound waves move fast through
vibrates ear drum
nerve impulses in
sound waves with frequencies above the normal
human range of hearing.
Sounds in the range from 20-100kHz
- sounds with frequencies below the
normal human range of hearing.
Sounds in the 20-200 Hz range
The apparent change in the frequency of a source of wave
due to the motion of the source and/or the observer
Developed by Christian Doppler in 1842
The difference of the true frequency and the apparent
frequency is called the Doppler Shift
The Doppler effect is the apparent change in the
frequency of sound due to the motion of source of sound
and/or the observer.
The following symbols will be used in the definitions:
fis the true frequency
is the apparent frequency
is the velocity of the sound (air)
is the velocity of the source
vo is the velocity of the observer
λ is the true wavelength
λ’ is the apparent wavelength
Case 1:observer is in motion and the
source is at rest
f ’ = [ ( v ± vo ) / v ] f
( + ) means the observer is moving towards the source
( - ) means the observer is moving away from the source
Case 2:observer is at rest and the source
is in motion
f ’ = [ v / ( v ± vs ) ] f
( + ) means the source is moving away from the observer
( - ) means the source is moving towards the observer
Case 3:both the observer and the source
are in motion
f ’ = [ ( v ± v o ) / ( v ± vs ) ] f
NOTE: please refer to case 1 and case 2 and
analyze the situation of the observer and the
When a wave source moves toward a receiver, does the
receiver encounter an increase in wave frequency, wave
speed ,or both?
Does the Doppler Effect occur for only some types of
waves or all types of waves?
in wave frequency caused
by a moving wave source
moving toward you pitch sounds higher
moving away from you pitch sounds lower
named after Austrian physicist and philosopher Ernst Mach
Used to describe speed of objects that are travelling close
to, or above the speed of sound.
The ratio of the speed of the object and the speed of
sound in the medium.
M = speed of object / speed of sound
this is heard as a sonic boom when an airplane passes
over; this is the result of the compilation of sound waves
generated by a source that moves at equal or greater
velocity than the sound it creates
An ambulance traveling at 20. m/s sounds its siren at a frequency of 256Hz.
What apparent frequency will you hear if the ambulance is:
( assume air temperature to be at 25°C )
a. approaching you?
b. moving away from you?
2. A car traveling at 30. m/s sounds its horn as it overtakes and pass another car
traveling at 20. m/s in the same direction. If the frequency of the horn is 500.
Hz, what is the frequency heard by the driver in the slower car:
b.) after the car has passed?
Assume sound speed to be at 350. m/s.
LIST OF REFFERENCES
This presentation is the combination of sources by the following:
Agatonlydelle. (2012). Physics Sounds. Online:
http://www.slideshare.net/agatonlydelle/physics-sounds. Accessed online on: 06
HMLSS21. (2012). Sound Waves BSU-ARASOF.
http://www.slideshare.net/HMLSS21/sound-waves-bsuarasof. Accessed online on:
05 march 2014
Marium S. (2013). DAV Lecture: WAVE INTERACTIONS. Online:
online on: 05 march 2014
Moral F. (2014). Teacher at B.R.I.G.H.T. Academy: The Doppler effects. Online:
http://www.slideshare.net/teacherfidel/16-the-doppler-effect?qid=c0a01b029c80-4a3c-861c-c18f4e6146e9&v=qf1&b=&from_search=2. Access online on: 05