This presentation is about sound waves and its types and more

1. Sound

2. Definition of SoundDefinition of Sound
Sound is a wave created by vibrating objects and
propagated through a medium from one location to
another.
Sound is a wave created by vibrating objects and
propagated through a medium from one location to
another.

3. If a tree falls in a forest, and thereIf a tree falls in a forest, and there
is no one there to hear it, does itis no one there to hear it, does it
make a sound?make a sound?
Based on our definition, thereBased on our definition, there ISIS
sound in the forest, whether asound in the forest, whether a
human is there to hear it or not!.human is there to hear it or not!.
Sound is aSound is a physicalphysical
disturbancedisturbance in a medium.in a medium.
Sound is aSound is a physicalphysical
disturbancedisturbance in a medium.in a medium.
A person to hear it is not required.A person to hear it is not required. The
medium (air) is required!

4. What type of waves are sound waves?

5. • The sound wave is transported from
one location to another by means of
particle-to-particle interaction.
• If the sound wave is moving
through air, then as one air particle
is displaced from its equilibrium
position, it exerts a push or pull on
its nearest neighbors, causing them
to be displaced from their
equilibrium position.
• Since a sound wave is a disturbance
that is transported through a
medium via the mechanism of
particle-to-particle interaction, a
sound wave is characterized as
a mechanical wave.
Review: Sound is a mechanical waveReview: Sound is a mechanical wave

6. A sound wave is different than a light wave in that a
sound wave is
a. produced by a vibrating object and a light wave is not.
b. not capable of traveling through a vacuum.
c. not capable of diffracting and a light wave is.
d. capable of existing with a variety of frequencies and a
light wave has a single frequency.
Check your understanding:Check your understanding:

7. When a tuning fork vibrates, it creates areas of highWhen a tuning fork vibrates, it creates areas of high
pressure (compressions) and low pressure (rarefactions).pressure (compressions) and low pressure (rarefactions).
As the tines of the fork vibrate back and forth, they push
on neighboring air particles. The forward motion of a tine
pushes air molecules horizontally to the right and the
backward retraction of the tine creates a low-pressure area
allowing the air particles to move back to the left.

8. Graphing a Sound Wave.Graphing a Sound Wave.
Sound as a pressure wave
The variation ofThe variation of pressurepressure withwith distancedistance is a useful way to represent ais a useful way to represent a
sound wave graphically. But remember – sound issound wave graphically. But remember – sound is actuallyactually aa
longitudinal wave.longitudinal wave.

9. A sound wave is a pressure wave; regions of high
pressure (compressions) and low pressure
(rarefactions) are established as the result of the
vibrations of the sound source. These compressions
and rarefactions result because sound
a. is more dense than air and thus has more inertia.
b. waves have a speed that is dependent only upon the
properties of the medium.
c. can be diffracted around obstacles.
d. vibrates longitudinally; the longitudinal movement
of air produces pressure fluctuations.
Check your understandingCheck your understanding

10. The vibrating object that creates sound could be the vocal
cords of a person, the vibrating string of a guitar or violin,
the vibrating tines of a tuning fork, or the vibrating
diaphragm of a radio speaker.
As a sound wave moves through a medium, each particle of
the medium vibrates at the same frequency. This makes
sense since each particle vibrates due to the motion of its
nearest neighbor.
And of course the frequency at which each particle vibrates
is the same as the frequency of the original source of the
sound wave.
Frequency of SoundFrequency of Sound

11. A guitar string vibrating at 500 Hz will set the air particles in
the room vibrating at the same frequency of 500 Hz, which
carries a sound signal to the ear of a listener, which is
detected as a 500 Hz sound wave.
Frequency of Sound ExampleFrequency of Sound Example

12. • We hear frequencies of sound as having differentWe hear frequencies of sound as having different
pitchpitch..
• A low frequency sound has a low pitch, like theA low frequency sound has a low pitch, like the
rumble of a big truck.rumble of a big truck.
• A high-frequency sound has a high pitch, like aA high-frequency sound has a high pitch, like a
whistle or siren.whistle or siren.
• In speech, women have higher fundamentalIn speech, women have higher fundamental
frequencies than men.frequencies than men.
The frequency of soundThe frequency of sound

13. Animation showing Frequency aAnimation showing Frequency a

14. Frequency of SoundFrequency of Sound
• The human ear is capable of detecting sound
waves with a wide range of frequencies, ranging
between approximately 20 Hz to 20 000 Hz.
• Any sound with a frequency below the audible
range of hearing (i.e., less than 20 Hz) is known
as an infrasound.
• Any sound with a frequency above the audible
range of hearing (i.e., more than 20 000 Hz) is
known as an ultrasound.

15. Ultrasound?
Ultrasound is a medical imaging technique that uses
high frequency sound waves and their echoes. The
technique is similar to the echolocation used by bats,
whales and dolphins.

16. How it works: Ultrasound
The ultrasound machine transmits high-frequency (1 to 5 megahertz)
sound pulses into your body using a probe.
The sound waves travel into your body and hit a boundary between
tissues (e.g. between fluid and soft tissue, soft tissue and bone).
Some of the sound waves get reflected back to the probe, while some
travel on further until they reach another boundary and get
reflected.
The reflected waves are picked up by the probe and relayed to the
machine.
The machine calculates the distance from the probe to the tissue or
organ (boundaries) using the speed of sound in tissue and the time
of the each echo's return (usually on the order of millionths of a
second).
The machine displays the distances and intensities of the echoes on the
screen, forming a two dimensional image like the one shown
below.

17. What about animals?
Dogs can detect frequencies as low
as approximately 50 Hz and as
high as 45 000 Hz.
Cats can detect frequencies as low
as approximately 45 Hz and as
high as 85 000 Hz.

18. Frequency and music
Certain sound waves when played (and heard)
simultaneously will produce a particularly
pleasant sensation when heard. Such sound waves
form the basis of intervals in music.
For example, any two sounds whose frequencies
make a 2:1 ratio are said to be separated by an
octave and result in a particularly pleasing
sensation when heard. That is, two sound waves
sound good when played together if one sound
has twice the frequency of the other.

19. Loudness

20. Intensity
Intensity: the rate at which a wave’s energy flows
through an area
Sound intensity depends on
 Amplitude
 Distance from source
Measured in decibels (dB)

21. Loudness is sort of like
intensity, but…
Loudness is Subjective! (This means it depends on
the person who is hearing it.)
Loudness is a personal, physical response to the
intensity of sound.
As intensity increases, so does loudness, but
loudness also depends on the listener’s ears
and brain.

22. Intensity is caused by the
Amplitude of the vibration
Example:
A vibrating guitar string forces surrounding air molecules to be
compressed and expanded.
The energy that is carried by the wave is imparted to the medium by
the vibrating string.
The amount of energy that is transferred to the medium is dependent
on the amplitude of vibrations of the guitar string.
If more energy is put into the plucking of the string, then the string
vibrates with a greater amplitude. The greater amplitude of
vibration of the guitar string thus imparts more energy to the
medium, causing air particles to be displaced a greater distance
from their rest position.

23. The Decibel Scale:
The decibel (abbreviated dB) is the unit used to measure the
intensity of a sound. The decibel scale is a little odd because
the human ear is incredibly sensitive. Your ears can hear
everything from your fingertip brushing lightly over your
skin to a loud jet engine . In terms of power, the sound of the
jet engine is about 1,000,000,000,000 times more powerful
than the smallest audible sound. That's a big difference!

24. The Decibel Scale
On the decibel scale, the smallest
audible sound (the threshold of
hearing) is 0 dB.
A sound 10 times more powerful is
10 dB.
A sound 100 times more powerful
than near total silence is 20 dB
A sound 1,000 times more powerful
than near total silence is 30 dB.

25. Intensity (Loudness) isIntensity (Loudness) is
measured in decibels:measured in decibels:
Source
Intensity
Level
# of Times
Greater Than TOH
Threshold of Hearing 0 dB 100
Rustling Leaves 10 dB 101
Whisper 20 dB 102
Normal Conversation 60 dB 106
Busy Street Traffic 70 dB 107
Vacuum Cleaner 80 dB 108
Large Orchestra 98 dB 109.8
Walkman at Maximum Level 100 dB 1010
Front Rows of Rock Concert 110 dB 1011
Threshold of Pain 130 dB 1013
Military Jet Takeoff 140 dB 1014
Instant Perforation of Eardrum 160 dB 1016

26. Check your understanding
A mosquito's buzz is often rated with a
decibel rating of 40 dB. Normal
conversation is often rated at 60 dB.
How many times more intense is
normal conversation compared to a
mosquito's buzz?