Whether you use ferrous or conduct sounds, you will still hear high tone "chirps", this is the hardest part of learning the Explorer, most of the other range is easy compared to this. What you have to learn is to recognise the iron falses from the true high non-ferrous conductors. Another possibility with all metal and ferrous sounds, the far lower right of the screen is open and will signal a high tone on such items like iron bottle caps, some users prefer to disc out that region so the highs don't come thru, this may be what you are experiencing. Some areas of the Country have hot rocks that can cause problems but since I don't have them here, I will defer to those who have learned to deal with them if that is what you are encountering. One method of dealing with high tones off iron is to turn 90 degrees and resweep, if you loose the high tone and it turns into a low tone, then there is a good possibility it is iron, with time though you may want to dig some of those "one angle" hits to see if you can pull a good item out of nails.