1. Waves

5. Periodic Wave
A wave whose displacement has a periodic variation with time or distance, or both.

7. Types of Waves
Electromagnetic:
Transverse:
Longitudinal:

9. Speed of Sound and Light
Speed of Sound in air
331 m/s
Speed of Light in a vacuum
3.0*10^8 m/s

10. How do we easily represent waves that move outward from a source?

11.
compression

12. What type of wave is a Sound wave?

13. Pitch Pitch is related mainly to the frequency of the sound
Pitch is not a physical property of the sound
Frequency is the stimulus and pitch is the response
It is a psychological reaction that allows humans to place the sound on a scale
Frequencies are exact, pitch can differ due to our human perception

14. Human hearing ranges

15. Pitch is the perception of frequency.
<20 Hz = infrasonic
Hz = audible
>20000 Hz = ultrasonic

16. Animal Hearing Ranges Humans hear “audible” sounds
Elephants can hear “subsonic” aka “infrasonic” waves (14-12,000 Hz)
Dogs can hear “supersonic” (67-45,000 Hz)
Test your own hearing range!
hear-this-hearing-test/

17. Intensity Level of Sound Waves
The louder the wave, the bigger the amplitude of the wave.
Loudness is measured in decibels (dB) or Watts per meter squared(W/m2).

18. Sound Intensity Try your hearing range at:

20. Speed of Sound in Air 331 m/s is the speed of sound at 0° C
T is the absolute temperature

21. When an object makes a sound, the sound waves propogate out in all directions. Assuming the object is stationary.

22. But what if that object is moving?

23. The apparent change in frequency of a wave caused by relative motion between the source of the wave and the observer.

24. Doppler Effect- Doppler Shift

25. Ultrasonic Sound
The term "ultrasonic" applied to sound refers to anything above the frequencies of audible sound, and nominally includes anything over 20,000 Hz. Frequencies used for medical diagnostic ultrasound scans extend to 10 MHz and beyond.

26. Shock Waves, final Video Clip
Shock waves carry energy concentrated on the surface of the cone, with correspondingly great pressure variations
A jet produces a shock wave seen as a fog
Video Clip

27. Forced Vibrations
A system with a driving force will force a vibration at its frequency
When the frequency of the driving force equals the natural frequency of the system, the system is said to be in resonance

28. Examples of Resonance Child being pushed on a swing Shattering glasses
Tacoma Narrows Bridge collapse due to oscillations by the wind
Upper deck of the Nimitz Freeway collapse due to the Loma Prieta earthquake

29. When something vibrates at its natural frequency, you get resonance!

30. Standing Waves
When a traveling wave reflects back on itself, it creates traveling waves in both directions
The wave and its reflection interfere according to the superposition principle
With exactly the right frequency, the wave will appear to stand still
This is called a standing wave

31. Harmonics
when an object is forced into resonance vibrations at one of its natural frequencies, it vibrates in a manner such that a standing wave pattern is formed within the object. These forced vibrations in an object are only created within the object or instrument at specific frequencies of vibration; these frequencies are known as harmonic frequencies, or merely harmonics.

32. Harmonics explained

33. For your instrument project….

34. Beats Beats are alternations in loudness, due to interference
Waves have slightly different frequencies and the time between constructive and destructive interference alternates
The beat frequency equals the difference in frequency between the two sources:

35. Quality of Sound – Tuning Fork
Tuning fork produces only the fundamental frequency

36. Quality of Sound – Flute
The same note played on a flute sounds differently
The second harmonic is very strong
The fourth harmonic is close in strength to the first