Yes, the headset mic sensitivity can be adjusted either up or down manually by adjusting the microphone gain via the rear panel to the right of the LCD screen.  Typically this control is set at mid level for normal speech levels.  When set in this manner the TALK/OM led will occasionally flash on on louder voice peaks.
If the audio input is too loud the led will be red during the complete word and the audio control should be adjusted slightly counter-clockwise to compensate accordingly. 
Use a small bladed screwdriver to adjust this control carefully. 
See photo below for location of this audio adjustment control.