Well that didn't take long.... RTFM applies, here. The manual for the headset emphasises that it is very important to ensure that the mic is 1/4" from the corner of the mouth. Using both headsets, we each spoke to the tower, being very careful regarding the mic position. Perfect transmissions. We then experimented in the cockpit only, and only a very small deviation from the correct position knocks the audio level down a lot. Whilst it was still quite acceptable in the cockpit, it obviously wasn't in a noisier environment without headsets.....
