The hardware structure of the automatic calibration system is shown in Figure 1. The signal generator (B&K 1054) generates sine excitation signal with proper amplitude and frequency. The power amplifier (B&K 2716C) amplifies the sine signal and sends it to the sound source
(loudspeaker). So the loudspeaker can produce sound in anechoic chamber or active coupler. The standard microphone receives sound signal and transforms it to electric signal. But the electric signal is too small to be measured by digital multimeter so it needs amplification. The measuring amplifier (B&K 2636) does that work. The digital multimeter (Agilent 34410A) receives and measures the signal from measuring amplifier. The camera is used to