Whenever I have heard the low volume beep I have made circles, walking. To try and detect it. The first initial beep can't even be replicated, though I did not test this to much. I have dug up treasures everywhere and know how it works. This that I report is not it. There is nothing in the plains that trigger the wishbone. The plains beep that i refer to triggered next to a small stone ruin far from any other biome.

I think there is a bug in the detection where it is constantly seeking and sometimes let loose one beep, albeit almost silent.

With how ship-wreck treasure is no longer detected and how it behave with the mountain burial tombs it seem like a bleeding item, maybe patch it up before it create permanent stains.

I would move this topic to bug section if I could.

No you probably ran over an underground buried treasure. The faster the beep, the closer you are. Were you around ruins or something?

typical tresures are 3-4 debth down when you use a pikaxe.
When it come to the snow biome then then you sometimes need to go deeper and look for it a bit harder to find the location of the silver below ground.
But yes its rather sensitive and can locating things from guess 50-100m away
So yes it could be you are in the max range and you only hear a single ping and then you know you have to run in another direction to find the tresure ( make it ping as fast as possible and then dig down ;-)

Destroy the chest and it should stop pinging. Just like once you hit the silver node with your pick axe it should stop pinging. The scrap iron in the swamp outside crypts can often be below the waterline and so pretty useless.