(v1.65W Stable -Ground Combat) Indefinite sound echo.

[Cloudish]

While in ground combat, an indefinite echo can be created, that lasts the entirety of the combat.

It happens, from what I remember, from foot steps.  A character walks walks, and then the sound of the steps never stops. It just keeps playing through all the turns, until combat is complete. It doesn't happen every combat, but a strong majority of them.