When people talk about the T/V/C distinctive audio, its more about telling the differnece between good targets and iron targets. With good headphones, and it sounds like you have covered that, bigger iron targets have a distinctive "snap" to them, a subtle crispness that good targets dont have. Good targets have a smooth, soft tone, repeatable no matter which way you sweep them. It may be that you dont hunt a lot of sites that have a lot of iron targets? Are you a park and yard hunter?
Most machines are fooled by large iron that has been in the ground a long time. Its actually the Halo that you are probably hearing. With the Tejon, often when I dig an "iffy" target, once I break up the halo the signal disappears. A medium size nail for example, deep, sometimes gives a questionable single when its in the ground, but once I disturb the halo, scanning the hole gives no signal and scanning the dirt pile gives no signal. Switch to all metal and I can locate the target. Now when that happens (lose the signal) I know immediately is a piece of iron.
Other junk targets, especially those that are irregular shapes, tend to have a sharpness to them too, but more so an irregular beep pattern. One sweep you might get a good signal but on the back swing it breaks up, and then continues to alternate depending on how you sweep it. You should dig enough of these to convince yourself they are usually trash.
But you must temper all of this with the site you are hunting. For example, if your on an 1830's military fort site, you will want to dig everything! In a neighborhood yard, you may only want to dig the strong repeatable signals. Or if your in the middle of a plowed field searching an old cabin site, where no one will care if you dig a lot of holes, again you would want to recover all of the questionable targets. Doing this, recovering some of the junk signals, often times allows you to find the good targets that might have been masked by the big piece of junk.
