Whether you'd call it a warble or not I don't know, but silver has a slightly softer/sweeter sound to it than clad if it's been in the ground a long time and not something you are air testing. I've dug silver with my GT that I just knew was going to be silver because the sound was just so sweet. Like anything else being able to hear that slight difference comes with practice. It is there, though. The Sovereign has the best, most telling, audio of any machine I've ever owned. You'll find it reports the characteristics of a target more than the shorter response of other machines. In fact, I've not used a machine that had such long drawn out descriptive audio. For instance, gold rings have a warm, round, soft, less harsh sound to them than a lot of junk does. Junk often will sound harsh, tinny, hollow, scratchy, etc. Of course these aren't hard and fast rules and I'm not saying it's easy to develope an ear for things, just like with any other machine.
Yes, the audio is modulated in that the deeper it gets the lower the volume.
Most say all the Sovereign models get about the same amount of depth, but some say the GT is just a tad bit deeper.
