When I record audio from the line-in jack on my laptop, what function of voltage produces recorded amplitude?
Since I've been told "voltage", unqualified: I apply a voltage square wave to a mono cable. (tip-sleeve switches between 0V and +5V every second). Since the voltage as a function of time is a square wave, why is the waveform of the recorded audio not a square wave?
And here's a recording of the same signal at 40Hz: