Built-in noise reduction circuit inverting precision ANC can effectively cut off 85% of the background noise; Dedicated high-quality noise-style 40mm diameter driver unit to ensure the highest quality; 3.7v lithium ion battery is rechargeable; Two modes: noise reduction state (need a battery) normal state (without battery) easy to switch; Earmuff is made of imported sponge soft and comfortable without fatigue for long wearing; Type: Active noise canceling headphone; Input terminal: DC 3.5DC plug; Working voltage: 3.7V; Maximum output power: 90mW; Noise level:18~20dB; Power supply: 120mA lithium battery; Rated operating time: > 20h; Noise reduction mode: dual-microphone noise feedback; Speaker diameter: 40mm; Speaker Impedance: 32phm; Speaker frequency response: 20Hz~20KHz; Speaker sensitivity: 115dB; Noise level: -78dBA; Dynamic range: 78dBA; Distortion THD: 0.1%; Stereo cross talk: -52dBA; Headphone wire length: PVC wire 1.5m