Violin Acoustics

1
Violin Acoustics

• Physics 332
• Prof. Hyde-Wright

2
Bowing,Stick-Slip Friction
Bow motion

• Bow at position L/n suppresses mode n1,2, or,
• Bow pulls on string until tension is too great.
• String completes one oscillation until string is
  again moving with bow
• Bow again pulls on string.
• Force of bow is automatically synchronized with
  oscillation.
• Shape of string is travelling triangle wave
• Dashed line envelope of apex.

3
Vibrations of Sounding Board and Back plate

• Holograms of vibration patterns at different
  frequencies

4
Violin Architecture

• (sideways) Vibration of strings transmitted to
  top plate via flexible bridge.
• Post, directly under side of bridge transmits
  vibrations to backplate.

5
Violin Acoustics

• Intensity response vs. frequency
• Bottom curve shows poor violin with tendancy to
  squawk due to excessive response at high
  frequency.

6
Violin/Viol Tuning

• Fifths (3/2 ratio)
• Violin G, D, A, E
• Viola C, G, D, A
• Cello, C, G, D, A
• Fourths (4/3 ratio)
• Double Bass E, A, D, G
• Viol (Renaissance) D, G, C, E, A, D

7
Harp

• C-major scale (multiple octaves)
• Shift all strings of one name up or down one half
  step with pedals

8
Stopped String harmonics

• Press string lightly a distance L/n from bridge
  to excite nth resonance

Stationary point for 2nd harmonic (n2)
Bow