1. Characteristic Frequencies and the Decay of Composite Sounds
Chapter 4
Characteristic Frequencies and the
Decay of Composite Sounds

2. Preliminary Hypothesis
Perhaps the hammer induces several frequencies on the skillet, whereas the soft object gives only one or few.

3. Tuning Fork
Strike near mid-point
Strike at the end

4. Superposition

5. Superposition
We step through the two waves horizontally, adding the vertical displacements at each horizontal step.

6. Harmonic Discriminator
Mic
Bandpass Filter
Skillet
Here we strike the skillet to produce impulsive sound, record the result with the mic, and select the frequencies we wish with the filter.

7. Waveform for the Skillet

8. Decaying Sound Frequency (F) Initial Amplitude (Amax)
Halving Time (T½)

9. Decaying Sound
Thumping the bottom of a plastic cup

10. VIBRATION OF A PENDULUM
Example - Metronome
What does the period (T) depend upon?
Length of the pendulum (l).
Acceleration due to gravity (g).
Period does not depend upon the bob mass or amplitude.

11. Pendulum Uses Timing Oil prospecting Walking
When oscillations are small, the motion is called simple harmonic motion (shm) and can be described by a simple sine curve.

12. Computer pendulum Experiment with the pendulum at this link
Another type of Simple Harmonic system