Hello everyone- After using Whites detectors for the last 25 yrs I finally decided to switch over to Minelab. I got my Explorer SE Pro in the mail yesterday. When I was playing with the settings I noticed that the threshold hum is only audible from 8-40. Anything below that and the threshold goes completely silent. Is this normal? I'm 66 yrs old but thankfully have very sensitive hearing and would like the threshold a couple of notches lower. I have a good RAT headphone and of course can lower the threshold by adjusting it's volume but I would think that the threshold would still be audible down to at least 3 or so for more flexability. This is whether I'm in factory preset or the program I have set up. Any advice would be appreciated. Gerry