Our first challenge was finding an inexpensive way to play sound files. This was difficult because the human ear is very good at determining when sound quality is poor. Good sound quality requires that lot of bytes of sound information be played very fast.
Our initial plan was to connect a custom micro-controller circuit board to a sound card from an inexpensive “talking” greeting card. These greeting card circuit boards can generally be purchased for a few dollars and that seemed like a reasonable idea.
The design worked, but also had some big problems. First, greeting card printed circuit boards are cheaply made because they are considered disposable. They are unreliable, difficult to program, and undocumented with regard to trying to control them.
Second, we were not able to find nice-looking switches that would fit into a frame that was only 1-1/4″ thick. To work around this issue we implemented a “proximity touch switch”. The user simply touched a location on the picture; the micro-controller would sense proximity and trigger the sound. In our initial testing with children and museum personnel we discovered that they really didn’t like the proximity switch. It did not provide the tactile feel of a real switch. The users couldn’t immediately tell if the switch had been pressed or not. This issue was made worse by a slight delay between the switch press and the sound being played. Users would push the switch over and over during the delay period.
Finally, we realized that the combined cost of the greeting card circuit board, a custom micro-controller printed circuit board and all the other parts such as the picture frame, speaker and picture was simply too high just to play one sound file. This lead to the development of the final product.