Controlling arduino with sound waves


I have a android tablet which I would like to be able to put on a little motorized wagon and control while I am connected to it through skype. I was thinking about transferring computer generated sound at some frequency not easily heard by humans, but still within the frequencies which skype transmits.

The arduino which controls the wagon would have some kind of microphone (or something else?) to receive the special sound, and decode it into commands like "go forward", "go back", "turn left", "turn right", "tilt upward" and "tilt downward". I would hope that these kinds of static commands could be transmitted and understood in parts of a second, preferrable 1/10s or less to make less of an impact on the ongoing conversation via skype.

There are a few reasons for me wanting to use sound as a means of pc to arduino communication: 1. I do not have to find and implement a "real" way for the arduino and the android tablet to communicate 2. I do not have to make programs in the tablet to communicate with the pc 3. I do not have to physically connect the tablet with the arduino in order to make this work. I just have to put the tablet on the wagon and off we go 4. It sounds like a fun little project which would teach me about sound waves

My questions would be something like this: Can anyone point me to something similar with people communicating to their hardware through sound waves? Would an amplified microphone connected with some nifty frequency filtering and recognition software inside the arduino be the best alternative, or is there already some kind of hardware which analyzes sound waves and makes them into something easier to read and understand for the arduino? Is the arduino A/D converter good enough for analyzing sound waves in this manner, or would I need an external A/D converter with higher resolution?

Cheers, Kim

Maybe this thread will help:,57073.0.html

Have you considered bluetooth? DOn't know if your tablet supports it?

I did consider btooth, but have decided against it for a couple of reasons. I believe the time needed to find a btooth hw compatible and to implement working communication both with the arduino and the pc via wan is much more than the time it would take to decode sound transmitted via skype. The tablet does not connect easily to btooth hw not specifically made for it (android galaxy tab)