How widely used are sonic fences beyond Tenebris? What's their niche, compared to the electric fence used by Clarke crew or other human barriers?
They are primarily used to establish large and wide scale boundaries against animals or sentients of various species. They can be tuned to specific species, or they can be set to a sort of wide band multi-frequency spectrum, but no matter the case, they tend to work by pulsing infrasonic frequencies projected in a directed cone outwards from the fence perimeter intended to cause acute discomfort to any living creature that gets too close. Usually electrical fences are employed between the sonic emitters to serve as a redundant barrier. They are typically quite effective against most forms of fauna, and are cheap to set up and maintain, so they are popular for use in areas with little development.