Sound is a form of energy that travels in waves from a vibrating object. It can travel through solids, liquids, and gases in the form of compression waves. The ear detects sound waves and transmits signals to the brain. Properties of sound waves include frequency, wavelength, amplitude, and pitch. The speed of sound depends on the medium and temperature, being fastest in solids and slowest in gases. Reflection and refraction of sound waves results in phenomena like echoes and resonance. Doppler effect changes the perceived frequency of a sound based on the motion of its source.

1. Did you hear that
SOUND?
Sound is a form of energy
that travels in
waves.

2. The Facts
Sound …
1. Is a form of energy produced &
transmitted by vibrating matter
2. Travels in waves
3. Travels more quickly through solids than
liquids or gases

3. The Ear
• Sound is carried to our ears through
vibrating air molecules.
• Our ears take in sound waves & turn them
into signals that go to our brains.
• Sound waves move through 3 parts of the
ear; outer ear, middle ear, & inner ear.
Middle Ear

4. Vibration
- Back and forth movement of molecules of
matter
- For example,

5. Compression
- Where molecules are being pressed
together as the sound waves move
through matter
- For example,
- a wave travels through the springs just like
sound waves travel through the air
- the places where the springs are close
together are like compressions in the air.

6. Sound Waves
- Alternating areas of high & low pressure
in the air
- ALL sound is carried through matter as
sound waves
- Sound waves move out in ALL directions
from a vibrating object

7. Sound Waves
• Each Sound wave
has unique pattern
• Frequency
• Wavelength
• Amplitude

8. Sound mediums
• A medium is a material that sound, a form of
energy, need to transfer
• Speed of sound
– Solid : Fast speed
– Liquid : Medium speed
– Gas : Slow Speed
• Standard Temperature and Pressure = 3.31 x 102
m/s
– Vacuum : No Sound

9. Wavelength & Frequency
- Wavelength is the distance between one
part of a wave and the same part of the
next wave
- Frequency is the number of waves moving
past a point in one second

10. Pitch
• A measure of how high or low a sound is
• Pitch depends on the frequency of a sound wave
• For example,
- Low pitch
- Low frequency
- Longer wavelength
- High pitch
- High frequency
- Shorter wavelength

11. Sound and Instruments
- Instruments can be played at different
pitches by changing lengths of different
parts.
- For example,
- Another way to make different pitches is
to change the thickness of the material
that vibrates.
- For example,
A trombone’s mute absorbs
some of the sound waves
produced, thus producing a
softer note when played.

12. Ultrasound
- sound waves with frequencies above the
normal human range of hearing.
Sounds in the range from 20-100kHz
Infrasound
- sounds with frequencies below the
normal human range of hearing.
Sounds in the 20-200 Hz range

14. Amplitude of Sound
• Volume control
• Loudness
• Strength of the wave ( measured in db “decibels”)
• Energy of the wave

15. Loudness of Sound in Decibels
Sound Loudness (dbs) Hearing
Damage
Average Home 40-50
Loud Music 90-100 After long
exposure
Rock Concert 115-120 Progressive
Jet Engine 120-170 Pain

16. Speed of Sound
• Velocity(v) of a wave= Frequency (f) times the
wavelength (λ)
• V = f λ
• The speed of sound depends on the
physical properties of the medium and
the temperature since the particle vibrate
faster when hotter sound can travel
faster.

17. Speed of Sound
• Medium velocity
m/sec
air (20 C) 343
air (0 C) 331
water (25 C) 1493
sea water 1533
diamond 12000
iron 5130
copper 3560
glass 5640

18. Reflection and Refractions of
Sound waves
• Echo
– Reflection of sound off a surface (Acoustics (Greek
akouein,”to hear”),. It is more commonly used for
the special branch of that PHYSICS that deals with
the construction of enclosed areas so as to enhance
the hearing of speech or music.
• Reverb (Electronic echo)
• Resonance
– electronic envelope Helmholtz Resonator, spherical
vessel of metal or glass with an opening and an
earpiece on opposite sides.
– The ear canal acts enhancing frequencies in the
range from 1000 to 4000 Hz (hertz, or cycles per
second).

19. Sonar
- An instrument that uses reflected sound
waves to find underwater objects
- For example,
Animals use sonar or echo location to find their
prey; these sounds have such a high pitch or
frequency that the human ear cannot hear
Humans use sonar
to locate or map
objects

20. Doppler Effect
•The frequency of the perceived
wave is changed by the motion of
the source
–Increasing Frequency when the
source approaches the sensor
–Decreasing Frequency when the
source increases the distance
from the sensor

21. That’s all folks!