1. Ch. 16 – Wave interaction II. The Nature of Sound Speed of Sound
Human hearing
Doppler effect
Seeing with sound

2. A. Speed of Sound 344 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

3. converted to nerve impulses in cochlea
B. Human Hearing
sound wave
vibrates ear drum
amplified by bones
converted to nerve impulses in cochlea

4. B. Human Hearing Pitch highness or lowness of a sound
depends on frequency of sound wave
human range: ,000 Hz
ultrasonic waves
subsonic waves

5. B. Human Hearing Intensity volume of sound
depends on energy (amplitude) of sound wave
measured in decibels (dB)

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

7. Diffraction Diffraction:
a change in the direction of a wave when the wave finds an obstacle or an edge, such as an opening
Examples:
Water waves diffract around a block in a tank of water.
Sound waves passing through a door diffract.

8. Wave interactions reflection:
the bouncing back of a ray of light, sound, or heat when the ray hits a surface that it does not go through
refraction:
the bending of a wavefront as the wavefront passes between two substances in which the speed of the wave differs

9. Constructive interference increases amplitude.
constructive interference: a superposition of two or more waves that produces an intensity equal to the sum of the intensities of the individual waves
Destructive interference decreases amplitude.
destructive interference: a superposition of two or more waves that produce an intensity equal to the difference of the intensities of the individual waves

10. C. Wave Interactions

11. D. Doppler Effect Doppler Effect
change in wave frequency caused by a moving wave source
moving toward you - pitch sounds higher
moving away from you - pitch sounds lower

12. D. Doppler Effect Stationary source Moving source Supersonic source
waves combine to produce a shock wave called a sonic boom
same frequency in all directions
higher frequency
lower frequency

13. “Sound Navigation Ranging”
D. Seeing with Sound
Ultrasonic waves - above 20,000 Hz
Medical Imaging
SONAR
“Sound Navigation Ranging”