noun
: a lens that brings sound waves to a focus (as by having walls of collodion film and being filled with a heavy gas which retards and consequently refracts sound waves)
noun
: a lens that brings sound waves to a focus (as by having walls of collodion film and being filled with a heavy gas which retards and consequently refracts sound waves)
Webster's New International English Dictionary. Новый международный словарь английского языка Webster. 2012