Can you hear me? Check out these cheap mics. Find them at digi-key , adafruit , sparkfun , or hands-free ear pieces. You will need to amplify the signal to read it in a micro-controller like arduino. Check out our ear-shaped amplifier breakout board tutorial. The mic will give you the present value of the sound wave. If you want to know the amplitude or volume, store some values in a buffer and find the variance or range of the buffer.