A signal processing system comprising: a plurality of microphone units configured to be connected in series, wherein each of the microphone units comprises: a microphone for picking up sound; a temporary storage memory ; and a processing section for processing the sound picked up by the microphone ; wherein the temporary storage memory is configured to temporarily store a sound signal processing program; wherein the processing section is configured to perform a process corresponding to the sound signal processing program temporarily stored in the temporary storage memory and to transmit the processed sound to a host device connected to one of the microphone units ; a host device connected to one of the microphone units, wherein the host device has a non-volatile memory in which a sound signal processing program for the microphone units is stored; wherein the host device is configured to transmit the sound signal processing program read from the non-volatile memory to each of the microphone units ; wherein each of the microphone units has a plurality of microphones having different sound pick-up directions and a sound level detector; wherein the host device has a speaker ; wherein the speaker is configured to emit a test sound wave toward each of the microphone units ; and wherein each of the microphone units is configured to judge the level of the test sound wave input to each of the microphones , to divide the level data serving as a result of the judgment into constant unit bit data and to transmit the unit bit data to the microphone unit connected as a higher order unit in the series connection, whereby the microphone units respectively cooperate to create serial data for level judgment. a plurality of microphone units configured to be connected in series, wherein each of the microphone units comprises: a microphone for picking up sound; a temporary storage memory ; and a processing section for processing the sound picked up by the microphone ; a microphone for picking up sound; a temporary storage memory ; and a processing section for processing the sound picked up by the microphone ; wherein the temporary storage memory is configured to temporarily store a sound signal processing program; wherein the processing section is configured to perform a process corresponding to the sound signal processing program temporarily stored in the temporary storage memory and to transmit the processed sound to a host device connected to one of the microphone units ; a host device connected to one of the microphone units, wherein the host device has a non-volatile memory in which a sound signal processing program for the microphone units is stored; wherein the host device is configured to transmit the sound signal processing program read from the non-volatile memory to each of the microphone units ; wherein each of the microphone units has a plurality of microphones having different sound pick-up directions and a sound level detector; wherein the host device has a speaker ; wherein the speaker is configured to emit a test sound wave toward each of the microphone units ; and wherein each of the microphone units is configured to judge the level of the test sound wave input to each of the microphones , to divide the level data serving as a result of the judgment into constant unit bit data and to transmit the unit bit data to the microphone unit connected as a higher order unit in the series connection, whereby the microphone units respectively cooperate to create serial data for level judgment. <EOS>