The time domain vs. the frequency domain #

As humans, we experience life as a progression of events, one after another in time. We can also describe the behavior of electromechanical systems this way, by saying things like, “The voltage started at 6 V, and then after 1 second rose to 12 V. As the voltage rose, the motor sped up, but it took a few seconds to reach full speed.” Time domain descriptions like this are generally a fine and sensible way of describing the world.

However, there’s another way to view the same world: the frequency domain. In many cases, it is totally useless. For example, do not say, “I really enjoy music with spread spectrum impulses approaching 2.9-3.0 Hz and strings vibrating in the 0-200 Hz range,” when you mean to say that you like drum ‘n’ bass.

But, there are other cases where the frequency domain provides an incisive view that is simpler and more insightful than a time domain description. The best example is filters.