ideally, this sticks to a window, and measures noise levels through a piezo (contact mic). the other piezo is set up to knock. the rgb is for output. on this prototype, you can use the red LED for visual indicator.
detail pictures show the traces running under resistors to keep it a single layer. the 68ohm resistor is 0805 and has 3 6mil traces with 1mil spacing tracked under. the 0ohm resistor has 4 6 mil traces running under it.