Sennheiser NoiseGard HMEC 300 Manual Del Usuario página 56

For positioning the microphone of the HMDC 322 headset, proceed as follows:
Adjust the length of the microphone boom so that the microphone is placed at the
corner of the mouth. To do so, loosen the quick-fixing device and adjust the
microphone boom in length.
Pull the middle part of the microphone boom towards the mouth so that the
distance between microphone and mouth is approx. 2 cm.
Tilt the microphone for final positioning.
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