No.lets assume the pc scope is DC-coupled
A sound card is not DC-coupled. It cuts off very low frequencies and does not pass DC.
The PWM waveform has an average DC voltage that changes. If it is DC-coupled then the top and bottom parts of the waveform will be straight lines (the supply voltage and almost 0V if a REAL comparator is used) but will move up and down (like you show) if AC-coupled.[/quote][/quote]