# Math/Physics Q: Voice Waveform Graph

Does anyone know what the units on the y-axis of this graph are supposed to be? I WAG the y-axis is the amplitude of the voice, I suppose? If so, then I WAG the scale is really arbitrary simply serving to portay the relative rises and falls in this visual representation of a voice? (The link should show two graphs. i refer tio the graph on the left).

x is time, y is amplitude.

And yes, the scale is arbitrary.

Yes, if by “amplitude” we mean air pressure somewhere in front of the person speaking. From the available information we might only guess that the Y axis scale units are arbitrary, though we might get a good guess at their units by looking up amplitude for the typical voice. The righthand graph would have as its vertical axis 1/10 of log10(energy/(area*DeltaFrequency)). The part about DeltaFrequency is required because without it we are suggesting there is energy perfectly confined to specific exact frequencies. I think there’s actually a standard meaning for “0 dB”, a particular value in terms of pressure, but don’t remember what it is.