We could, in principle at least. find the impulse response experimentally by actually applying an impulse at the system input. But. since a true impulse cannot actually be generated. this would only be an approximation. Also. in practice an approximation to an impulse would be a very tall pulse lasting for a very short time. ln reality. for a real physical system, a very tall pulse might actually drive it into a nonlinear mode of response. and the experimentally measured impulse response would not be accurate. There are other less direct but more practical ways of experimentally determining an impulse response.