Logitech H540 USB Headset 

• Microphone Type: Bi-directional
• Input Impedance: 20 Ohms
• Sensitivity (headphone): 115 dB +/-3 dB
• Sensitivity (microphone): -42 dBV/Pa +/- 3 dB
• Frequency response (Headset): 20 Hz - 20 KHz
• Frequency response (Microphone): 100 Hz - 16 KHz