This javascript app calculates an online cochleagram from the input to your computer's microphone. (You may have to adjust the sensitivity a bit.) A cochleagram is a better representation of the activity pattern that auditory nerve fibers send to your brain than the simple spectrogram you may have seen under the acoustics section. It takes into account the approximately logarithmic frequency distribution along the basilar membrane, as well as the changing cochlear filter bandwidths as a function of frequency. You can use this spectrogram app to visualize what various sounds or speech would "look like" to your brain. You can pause the spectrogram by clicking on it.
Making sense of sound