1. RESONANCE MUSICAL ACOUSTICS Science of Sound Chapter 4

2. Resonance Resonance occurs when a vibrating system is driven at its natural frequency. The amplitude of the vibrator reaches a maximum, limited only by the damping.

3. PHASE DIFFERENCE BETWEEN CRANK AND MASS

4. STANDING WAVES ON A STRING

5. OPEN AND CLOSED PIPES OPEN PIPE CLOSED PIPE

6. STANDING WAVES IN CYLINDRICAL AND CONICAL PIPES

7. ACOUSTIC IMPEDANCE Acoustic impedance is the ratio of sound pressure p to volume velocity U Z A = p/U

8. GRAPHING ACOUSTIC IMPEDANCE APPARATUS FOR GRAPHING THE ACOUSTIC IMPEDANCE OF WIND INSTRUMENTS

9. HELMHOLTZ RESONATOR

11. TUNING FORK D.A. Russell, "On the sound field radiated by a tuning fork," Am. J. Phys., 68(12), 1139-45 (2000).

12. CHOIRCHIMES

13. CHOIRCHIME VIBRATIONS

14. SINGING RODS AND WINEGLASSES

15. SINGING RODS In a bar or rod with free ends the fundamental mode will have a node at its center, and the maximum vibration occurs at the ends (just as in a pipe open at both ends). The next mode has two modes at ¼ L and ¾ L Stroking an aluminum rod with the fingers to excite these longitudinal resonances can create rather loud sounds

16. SELF-EXCITATION A linear force or motion can excite vibratory motion by a process called self-excitation. Examples of this are the stick-slip motion that excites a wineglass or a violin string

17. SELF-EXCITATION A linear force or motion can excite vibratory motion by a process called self-excitation. Examples of this are the stick-slip motion that excites a wineglass or a violin string

18. COLLAPSE OF THE TACOMA NARROWS BRIDGE A DRAMATIC CASE OF SELF-EXCITED OSCILLATION

19. SYMPATHETIC VIBRATION The vibrating string of a piano or guitar excites the soundboard to vibrate (and thus to produce much more sound). This is called sympathetic vibration. Sympathetic vibration and self-excitation of vibration should not be confused with resonance.

20. Assignment for January 21 Read Chapter 5 Exercises 1-8 (p.73) For extra credit: Driven harmonic analyzer (“Texas tower”) Make a graphs of amplitude vs frequency and phase angle vs frequency for 2 amounts of damping Show the modes of a wineglass that can be excited by rubbing with a finger; bowing radially with a violin bow; driving it with a loudspeaker. Ref: J. Acoust. Soc. Am. 95, 1108-1111 (1994).