In audio the term knee refers to a point where the response of some system or function exhibits a notable change. (The name comes from the human body part, because when these things are plotted on a graph the resulting line sometimes resembles a somewhat bent human leg, where the knee joint represents a change in behavior.) For example, in an audio compressor the threshold setting creates a knee at a particular level inside the compressor as it relates to the dynamic range of any passing audio. Below this knee the compressor will exhibit a different behavior than above the knee. The term “soft knee” was coined to describe circuit behaviors where the change is smoothed out over a finite range of levels.