No matter why you fly, the Bose A20 Aviation Headset is engineered to improve the experience. It provides 30% greater noise reduction than conventional aviation headsets, which helps you stay focused on your flying. It provides clear audio with active equalization. And its minimal clamping force makes even your longest flights more comfortable. In addition, the A20 headset offers a high-performance electret microphone, customizable audio prioritization control with “mute” and “mix” settings and simple, intuitive operation for plug-and-fly convenience. You can choose the left or right ear cup to connect the mic. The A20 headset is certified to FAA TSO C139 standards. It's among the lightest of all active noise cancelling headsets, with a weight of just 12 ounces. No other headset offers this unique combination of features and benefits. Bluetooth wireless technology is 3.1. Troubleshoot-cannot hear intercom communications while listening to audio from aux source make sure the headset is firmly connected to the intercom or radio system. Make sure the 0.14 inch aux audio cable is firmly connected to the control module and the aux source. Electret microphone sensitivity varies depending on bias and ac radio input impedance. Typical output is 600 mv at 114 db spl. To assure proper modulation of the radio, it is recommended that an avionics technician adjusts its input to match the output of the microphone. Dynamic microphone impedance is 5 ohm or 150 ohm dynamic mic and sensitivity is equivalent to m-87/m-101