1. Sound resonance To every system, if it is disturbed and let free to oscillate by itself, the system will oscillate at its natural frequency e.g. pendulum

2. If a system is oscillating at its natural frequency, and energy is add to it at a frequency = natural frequency of the system The system will absorb the energy at 100% efficiency System will oscillate at increasing amplitude What will happen then?

3. Sound + wine glass 1 Sound + wine glass 2 Tacoma Narrows Bridge Story

4. Can we “see” sound waves? We can “see” sound waves by using a CRO CRO = Cathode Ray Oscilloscope

5. Musical notes and noises (Page 282) The waveforms of notes are regular. The waveforms of noises are irregular. Tuning fork Mouth organNoise

6. The higher the frequency, the higher the pitch. The loudness of a musical note is related to the amplitude and frequency. For two musical notes of the same frequency, the one with a larger amplitude is louder.

7. Different musical notes played by different instruments have different waveforms and thus different qualities. CRO traces (by oboe) CRO traces (by French horn)

8. Oboe 雙簧管 French horn 法國號 Page 283 Ex. P.288 (5)