I knew a guy who did a several month study in a junky park in San Jose, CA. He gridded off a part of a park which had been picked hard for silver over the years. Ie.: everyone cherry picking for high conductors in past years. Hence passing foil, tabs, nickels, etc... My friend reasoned based on the amount of old coins that used to come out of here, there's GOT to be some old nickels and gold still here. So he gridded off a big section. And ..... for the next few months .... forced himself to strip-mine ever single signal. He kept careful diary records of each item. Eg.: type object, depth, location, etc.... In the end, yes.... he did get some buffalos and a V or two (all numismatically worthless orange-ish corroded). And he did get some gold items: A few rings, charms, etc.... But he concluded it simply wasn't worth the strip-mining time that it took. And that his time would have been better spent simply going to the beach, if gold were his objective.
But one interesting lesson his study played out though: When taking meticulous study notes of depth of each item, he would purposefully dig slow for each object. And he noticed that whenever he got a gold ring, that .... IF the ring had a "crown" on it, then it would always be tilted towards the heavy end down. Only the round even bands would be flat in the ground. Hmmmm. So therefore this might be something to consider for those who are trying to discern a ring sound via a "round" sound. To be totally fair, you'd have to be trying rings tilted, not just flat on a table.
Postscript: The dealer fellow in the video never answered my email, asking him to answer the critique. And so goes these claims, eh ? People (even dealers) spout this stuff, but then disappear when the notions are challenged.