Sensitivity adjusts the Demodulators and will decrease reception of stray RF signals. However, the first adjustment should be NOISE Cancel. Also, stray RF signals will sometime not be present if all we do is turn 90 degree less or more as the RF and our detector are very directional. If we cannot reduce the noise then the reduction of sensitivity will do the trick. If in manual sensitivity we can almost always correct the problem with Semi-auto. How we do this is up to the individual. What is important is that we have the greatest actual sensitivity when the detector is stable. An indication of stability is when the threshold is does not have a scratchy sound.
Sensitivity for the most part has two functions. One is to adjust sensitivity as I posted and the other is to balance one leg of the demodulators so ground noise, aging of electronics, temperature variations, changes in the coils Q, are compensated for. We know when this is done and ground noise and stray RF is compensated for when the threshold is stable.
NOISE CANCEL is mostly for stray RF. Sensitivity is mostly for Ground noise. Audio Gain is for audio gain just as it tells us.
Have a great weekend,