Masking
Suppose you enter a restaurant with a friend, mid-conversation. As you enter, you are greeted by the background noise of other patrons’ conversations. You and your friend begin to speak louder so you can hear one another. You’ve just experienced masking, a very familiar yet fascinating phenomenon that many of us encounter every day without even noticing.
Spectrogram
Just as a frequency spectrum makes it possible to analyze the partials and noise components that make up a sound, a spectrogram can be used to visualize the evolution of these components of a sound over time. The first modern device able to produce such a representation of sound was the “sound spectrograph,” developed at Bell Telephone Laboratories in the 1940s [1]. A spectrogram has a very intuitive way of displaying its parameters. Just as in a musical score, time is represented on the x-axis, frequency on the y-axis, and energy/amplitude is determined by the intensity/hue of the colors.