Gobblers Gobble for many reasons, the difference between a Shock Gobble, and any other gobble, is it is Triggered, by what ever Triggers it, Loud noise, Frequency?, who really knows, but it is Triggered.
Gobblers Gobble on the roost, to let the Turkeys/Hens, flock, know where he is, he gobbles like a Sentinal, to Locate, to Sew His Oat's, to show dominance, Just to Gobble, he is a Turkey, thats what he does.
Quickest explanation to your question would be, One is Triggered, ( Shock Gobbling ) and the Others, are not, they are made for a specific reason, mebe, He is just in a good mood that day.

I am not, nor do I want to drag this out into a mess anymore than it is, but that is a pretty easy question to answer Shad, the difference between a Shock Gobble, and other Reasons for Gobbling.
I understand the Gobbling in Unison Deal, but 99% of the time, when that is done, it is a Triggered, shock gobble, it is an Instinc that is breed into them.
To even TRY, and Understand, or narrow down to WHAT noises TRIGGER, or Frequency Triggers, and so forth, is and would be never ending.
Just my 2 cents worth, do not want to argue or statrt anything, pretty simple answer though really.