Figure 1. A three-axis plot showing the decay of the typical kick-drum sound energy over time, by octave band. Note that the attack is present across the whole spectrum (in reality it depends on the hardness of the beater), so that the kick drum should be thought of as a broad spectrum sound. Note also that the low frequencies can sustain. In practice, they are often damped, in order to cut off that sustain, shortening the sound down to perhaps as little as 250 ms.