1. The Physics of Sound

2. A disturbance that travels through a medium as a longitudinal wave.
Sound
A disturbance that travels through a medium as a longitudinal wave.

3. The Physics of Sound Longitudinal Wave

4. The Physics of Sound

5. How sound travels Sound waves carry energy through a medium.
Each particle of the medium vibrates as the disturbance passes.
When the disturbance reaches your ears, you hear the sound.

6. Interactions of Sound Waves
Reflection – when an object or a wave hits a surface through which it cannot pass, it bounces back.
*A reflected sound wave is called an ECHO.
Diffraction - the spreading or bending of a wave through a small opening or around a corner.

7. Speed of Sound 343 m/s in air at 20°C Depends on: Type of medium
travels better through liquids and solids
can’t travel through a vacuum
Temperature of medium
travels faster at higher temps

8. Sound depends on 2 factors
Properties of Sound
Loudness – describes what you hear and is measured in decibels (dB)
Sound depends on 2 factors
The amount of energy it takes to make the sound
the greater the energy the louder the sound
larger amplitude = larger sound
The distance from the source of the sound
loudness increases the closer you are to the source
a sound wave of greater intensity sounds louder

9. Human Hearing
DECIBEL SCALE
120
110
100 80 70 40 18 10

10. Properties of Sound
Pitch – a description of how high or how low the sound seems to a person
Depends on the frequency of the sound wave
high frequency = high pitch
low frequency = low pitch
Changing Pitch
use vocal cords located in larynx to change sounds
stretched vocal cords = higher frequency sound with high pitch
relaxed vocal cords = lower frequency sound with low pitch

11. Doppler Effect the change in frequency due to the relative
motion of the wave source and the observer
The observed frequency is higher when the
source and observer are getting closer.
The observed frequency is lower when the
source and observer are getting farther away.

12. What causes the Doppler Effect?
When a sound source moves, the frequency of the waves changes because the motion of the source adds to the motion of the waves.
As source moves toward listener the frequency of the waves is higher

13. The Doppler Effect
can be evident for
all types of waves –
including light,
sound, water, etc…

14. Using Sound
Echolocation – the use of reflected sound waves to determine distances or locate objects.
Some animals, including bats and dolphins, use echolocation to navigate and to find food.

15. Using Sound
Ultrasound technologies such as sonar and ultrasound imaging are used to observe things that cannot be seen directly.

16. Using Sound
Ultrasound imaging – devices send ultrasound waves into the body and detect the reflected sound waves. The device uses the reflected ultrasound waves to create a picture called a sonogram.
Sonar – a system that uses reflected sound waves to detect and locate objects underwater.
Sonar is used to determine the depth of water, to map the ocean floor, and to locate sunken ships, schools of fish, and other objects in the ocean.

17. “Sound Navigation Ranging”
“Seeing” with Sound
Medical Imaging
SONAR
“Sound Navigation Ranging”