Arduino recognize specific sound?
As stated in other answers, sound recognition is completely out of the
realm of what an Arduino can do, but recognizing a specific pitch is
possible.
However, contrary to previous answers, I would recommend against using
an FFT. The FFT is the right tool when you need to get all the
frequency components. It is, however, overkill when you want to look at
a single frequency. Given the low processing power at your disposal, I
suggest you try instead an homodyne detection scheme. An Arduino
Uno, or similar board, has enough resources to sample an input at
9.6 kHz, and extract in real time a specific frequency component.
See for example this homodyne detection program.