Caves are certainly not anechoic chambers. Anechoic chambers are called that because they have no internal reflection (no echos, an-echoic). Caves may be highly

Caves are certainly not anechoic chambers. Anechoic chambers are called that because they have no internal reflection (no echos, an-echoic). Caves may be highly insulated from the rest of the world, but their rock walls are highly reflective. An anechoic chambers sounds weird because there is practically no natural analogue.