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Why does a violin sound different from a horn?
Several kinds of audible information
Pitch
Timbre
Attack
Decay
Vibrato
Thus, we need to quantify sound
Thus, we need to measure sound
We need to systematically compare sounds…
The Waveform• Plot motion of air (pressure vs. time)
time (ms)
pres
sure
• Microphone converts pressure to voltage
Compare Waveforms
period
T = 2.2 ms
T = 7 ms f = 1/T = 140 Hz
f = 1/T = 460 Hz
pure tone sine wave
• Single period implies a single, constant frequency• Described by only two numbers: f, A
ampl
itud
e
period
How can we describe more complicated sounds?
simplest sound simplest waveform