Sonic HP259 Stereo Headset with Microphone Frequency Response: 20-20000 HZ Impedance: Headphone: 32 Ohms Mic: U=3V, R=1.5K Sensitivity: Headphone: 105dB/mW Mic: -58dB&#plusum;2dB Power Heading Capacity: 1000mw Rated Power: 100mw