As promised in class, I've uploaded here a sound file (mp3) demonstrating the logarithmic sensitivity of human hearing. The first sample of sound is white noise; the second sample is the same noise, with the voltage reduced by a factor of the square root of 2. That is, the voltage decreases exponentially: it falls by 50% every second sample. Though, for us it sounds as if it decreases linearly.
Check the following link for more explanations.