1. Sound and Hearing

2. Properties of Sound Waves
• What type of waves are sound waves?

3. Properties
Sounds behave in certain ways
because of the properties of sound
waves. Some properties are:
• Speed
• Intensity & Loudness
• Frequency & Pitch
• Timber or quality

4. Speed
• Speed of sound = 331 m/s
• Sound speed varies, depending on
medium
– Travel fastest in solids, slowest in gases
– Travel fastest in the most dense media
– Speed of Sound animation

5. Speed of sound in different
materials
Materials
Air (0 ͦ C)
He (0 ͦ C)
H (20 ͦ C)
Water
Seawater
Iron and Steel
Aluminum
Hard wood
Speed of Sound (m/s)
• 331
• 1005
• 1300
• 1440
• 1560
• 5000
• 5100
• 4000

6. 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)

8. Source of sound
Level (dB)
Jet engine, 30 m away
140
Threshold of pain
120
Amplified rock music
115
Old subway train
100
Average factory
90
Busy street traffic
70
Normal conversation
60
Library
40
Close whisper
20
Normal breathing
10
Threshold of hearing
0

9. Loudness
• 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.

11. Frequency & Pitch
• Frequency of a sound wave depends on
how fast the source of the sound is
vibrating.
• Pitch is how we hear frequency of sound
waves
• Pitch depends on frequency…high
frequency sounds are high pitched, and
low frequency sounds are low pitched.
• Pitch also depends on age and health

12. Frequency and
Pitch animation

13. Timber
color or tone quality-used to
distinguished between two
different sounds that have the
same pitch and loudness

14. The Doppler Effect
• Where have you heard of the term
“Doppler”?
• Doppler Effect: a change in sound
frequency (pitch) caused by the motion of
the sound source, the listener, or both
• Why do we observe this?
• Doppler Effect animation

15. • Refraction of sound-change in
direction, as the wave moves
from one medium to another- It
bends or refracts as they move
through air.
• Sound waves refract.

16. • Reflection of sound
• Echo- reflected sound - it is what
you heard shortly after the original
• Diffraction of Sound- Sound
waves bend or diffract around
corners or barriers like doors and
walls.

17. • waves overlapping are the result
of two or more sound
INTERFERENCE.
2 types
• Constructive interference-the
sound waves arrive at the same
time and phase
• Destructive interference-waves
arrive at interval and are out of
phase

18. • Resonance - the inducing of
vibrations of a natural rate by a
vibrating source having the same
frequency.

19. Hearing and the Ear
• Your ear has a membrane that vibrates when
sound waves hit it…what is this membrane?

20. Hearing & the Ear
Ear consists of 3 main parts
• Outer Ear – gathers and focuses
sound
• Middle Ear – receives and amplifies
vibrations
• Inner Ear – uses nerve endings to
sense vibrations and send signals to
the brain

22. • Most people hear sounds between 20 and
20,000 Hz.
– Infrasound – sound at frequencies lower than
people usually hear
– Ultrasound – sound at frequencies higher
than people usually hear
• Used in technologies such as sonar and
ultrasound imaging

23. • Sonar – a technique used to determine the
distance to an object under water.
• Ultrasound – medical technique used to
take pictures of different organs (or a
fetus!)

25. I HOPE YOU LIKE !!! <3