¡ìAcoustic noise Hi-Fi¡ìDSP built-in noise reduction circuitDynamic closed-circuit noise¡ìAGC circuit built-in gain¡ìTone processing circuit¡ì no noise10~150m2 AdjustableImpedance of 600 ohms Frequency 20 ~ 20Khz 9 ~ 12VDC power supply ¦µ72 * 41mm size