1. In multi-pulse coding of a speech signal, a method of reducing the amount of calculation that is necessary for conducting a pulse search, said method comprising the steps of: adding crosscorrelations between an impulse response of a synthetic filter without pitch prediction and an impulse response of a synthetic filter with pitch prediction, thereby determining autocorrelations of the impulse response of said synthetic filter with pitch prediction; and adding crosscorrelations between the impulse response of said synthetic filter without pitch prediction and an input speech signal to determine crosscorrelations between the impulse reponse of said synthetic filter with pitch prediction and the input speech signal.