Physics 221

ELEMENTS OF PHYSICS I
Physics 221

CHAPTER 12
Sound

NEW CONCEPTS

pitch
audible range
intensity (loudness)
intensity level
musical instruments
- fundamental frequency
- overtones (harmonics)
- open tube
- closed tube
beats
Doppler effect

FORMULAS

Speed of sound in air at 20^o C: v = 343 m/s.

Audible range of frequencies for humans: 20 to 20,000 Hz.

Audible range of intensities for humans: I₀ = 10^-12 W/m² to 1 W/m².

Intensity level:

$\begin{displaymath}\beta = 10\, \log (I/I_0)\end{displaymath}$

String harmonics: f = nf₀

Open tube harmonics: f = 2nf₀

Closed (at one end) tube harmonics: f = (2n+1)f₀

where f₀ is the fundamental frequency and n=1,2,3,....

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