1. Pulling it together or apart!
Lecture 13
Pulling it together or
apart!

2. What’s Up?
This week we will continue our discussion of the stringed instruments and will also return to the idea of how the musical scale was created.
The exam is scheduled for Friday. Bring a calculator.
There is a brief study guide on the website. Equations in red will be supplied.
The exam includes material discussed today but NOT on Wednesday.

3. Where are we?
Last week we discussed the various parts of the guitar and what they did.
We have discussed “standing waves” but not how they actually form.
We discussed the formation of the interval of the “fifth”, a very important CONSONANCE.
Let’s continue from there……..

4. Reference Material http://www.phys.unsw.edu.au/~jw/strings.html
(Includes some math .. Sine, cosine, log, etc.

5. Remember Reflection?? FIXED END Initial Pulse
Reflection is inverted because of the forces of the wall on the string.
Return Pulse

6. PLUCK!
Waves

7. Adding Waves

8. A look at the string

9. A look at the string

10. Harmonic Waves T

11. Tension Adjustment

12. More than one frequency is produced!
Guitar Spectrum

13. The sound envelope

14. Pluck it.
Center
Bridge
(twangy)

15. Timbre

16. More Timbre

17. The Bridge Thingy

18. The bridge
Connects (couples) the string to the top plate of the guitar resonator box.
The motion of the top plate sends sound waves out to the listener.
Waves INSIDE the box are also created and the ones that have a “resonant frequency” that matches the box will be amplified like a Helmholtz resonator.
The guitar box has many resonant frequencies!

19. Top Plate Holography (whatever that is)

20. Similar Instruments

21. Violin

22. Violin – Where are the frets??

23. The “Box Resonance” for a string instrument

24. Violin Bridge

25. Violin

26. The Bridge

27. What happens when we play two strings together?
L L2