From the July 13, 1935, issue
By Science News
SOUNDPROOFING GIVES WALL LOOK OF UNDERGROUND CAVE
The microphone shown on the front cover of this week’s Science News Letter is not broadcasting from among the stalactites of some underground cavern. The curious formations shown are nothing more romantic than cotton waste covering the walls and ceiling of a soundproof room in the General Electric Company’s general engineering laboratory at Schenectady, N.Y.
The waste is thus used to minimize reflection and resonance of sound generated within the room. Sensitive sound-measuring instruments are calibrated there and then taken to another soundproof room to determine the amount and types of noise prevalent in motors and other electrical apparatus.