Transient response is the reaction of an electronic circuit, or electromechanical device, or acoustic space to a non-repetitive stimulus such as a step or impulse response. It is the result to a sudden change in the input that is nonperiodic. For example, percussive instruments produce primarily transient sounds. The transient stimulus and resulting response are characterized by the amplitude and the rise time (and fall time if it is an impulse), overshoot, and settling time. The standard reference is to note the maximum amplitude and the time required to reach within 10% of the steady-state value.