L26 Music & Interference

Review of Sound Waves

Standing Sound Waves

Viewgraphs (Knight)(103-1 fr 24; 107-1 fr 55)

Boundary Conditions

Close-Close	Close-Open	Open-Open
f = m v / 2L (m=1,2,3...)	f = mv/4L (m=1,3,5...)	f = m v / 2L (m=1,2,3...)

Musical Instruments

Open vs Closed pipes: Flutes vs Clarinets

Example: Find Ear Canal Resonant Frequency (Standing Wave)

L_{ear canal} = [2 2.5] cm; v_sound~330 m/s
for open-close tube → f_m = m v / 4L (m=1,3,5...)
f₁ ~ 330/0.1 ~ 3300Hz
f₃ ~ 10kHz   f₅ ~ 16kHz

Interference in General

1. 1D
2. 2D and 3D
3. Beats