Why Sound Waves - Why NOT just data?

[prototrout]

(It looks like the question was answered while I was writing up my reply; I'm leaving it because it goes into a little more detail.)

It's not using sound waves exactly, it's just using the sound card to send an (analog) electric signal.

The printer has to somehow move the mirrors to control its laser. It does that using electromagnets, and it moves the electromagnets using an electric signal on a wire. It needs some way to convert commands that describe what to print into signals for the electromagnets.

Now it could do what you say: receive commands over USB (or some other digital interface with the computer) and have electronics on board that interpret that digital signal and convert it into an analog signal that controls the magnets. But just about every computer already has something that converts digital signals to analog: their sound cards. Sound cards generate an analog signal that moves an electromagnet in the speaker, which generates sound -- almost the same job the Peachy Printer needs done, just moving a speaker diaphragm instead of a mirror. By using a host computer's sound card to do the job, the printer doesn't need any electronics on board: it can just hook the electromagnets directly to the speaker wire. It ends up being a lot simpler and cheaper.

So in short, the sound card does a job that the printer would have to do anyway. By letting that job be done on the host computer, the Peachy Printer can be less expensive and less complicated.