Confirm the legality. It may pertain to a certain type of hunting I.E. predator hunting and such.

But for squirrels the quarter or nickel setup is fine. it has worked in the past and will work in the future. When it comes to anything else though i would go with things more natural.

People don't hear in the full ranges that animals can and don't notice these things but animals can actually pick up on the hum and undetected feedback speakers often generate. When i say feedback i'm not talking about when you get a mic next to a stage amp but even when your app or whatever if between say grunts. It is still applying power to the speaker and that minute power will still cause vibrations in the speaker, though we hear nothing an animal could possibly pick it up. This is why predator calls are made in a particular way to amplify sounds but also dampen the silence between sounds.

Distortion from recording may be a better word.