A signal processing system comprising: a plurality of microphone units (2A, 2B, 2C, 2D, 2E) configured to be connected in series, wherein each of the microphone units (2A, 2B, 2C, 2D, 2E) 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 (2A, 2B, 2C, 2D, 2E); 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 (2A, 2B, 2C, 2D, 2E) 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 (2A, 2B, 2C, 2D, 2E); wherein each of the microphone units (2A, 2B, 2C, 2D, 2E) 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 (2A, 2B, 2C, 2D, 2E); and wherein each of the microphone units (2A, 2B, 2C, 2D, 2E) 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 (2A, 2B, 2C, 2D, 2E) connected as a higher order unit in the series connection, whereby the microphone units (2A, 2B, 2C, 2D, 2E) respectively cooperate to create serial data for level judgment. a plurality of microphone units (2A, 2B, 2C, 2D, 2E) configured to be connected in series, wherein each of the microphone units (2A, 2B, 2C, 2D, 2E) 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 (2A, 2B, 2C, 2D, 2E); 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 (2A, 2B, 2C, 2D, 2E) 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 (2A, 2B, 2C, 2D, 2E); wherein each of the microphone units (2A, 2B, 2C, 2D, 2E) 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 (2A, 2B, 2C, 2D, 2E); and wherein each of the microphone units (2A, 2B, 2C, 2D, 2E) 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 (2A, 2B, 2C, 2D, 2E) connected as a higher order unit in the series connection, whereby the microphone units (2A, 2B, 2C, 2D, 2E) respectively cooperate to create serial data for level judgment.