The Waveform

time (ms)

pres

sure

• Microphone converts pressure to voltage• Plot pressure vs. time• Sound always has an oscillating pressure vs. time

Compare Waveforms

period

T = 2.2 ms

T = 7 ms f = 1/T = 140 Hz

f = 1/T = 460 Hz

pure tone = sine wave

• Definite period single, constant frequency• Described by only two numbers: f, A

ampl

itude

period

How can we describe more complicated sounds?What creates a sine wave?