If scientists' ears were keen enough to distinguish the different sound-waves in the noise caused by a street car, they might be able to cause other sound-waves to neutralize the din. Last week Dr. J. P. Foltz, engineer, invited scientists to the Westinghouse Research Laboratories, East Pittsburgh, Pa. to show them a small contraption which could analyze the street car's rattle-bang-clank-screech. The machine consists of a microphone, an amplifier, a filter circuit which allows only one wavelength at a time to pass to the meter for measuring. Since the machine weighs only 60 lb., is independent of outside current, it can easily be transported from one noisy place to another.
Dr. Foltz expects that his machine will be able to analyze all city noises so that scientists will know what wavelengths to produce to have a quiet city. Said he: It is entirely possible to produce silence by two sound-waves which fit into each other much like the teeth of two saw blades. The "electric ear" will also be used to test machines for friction, loose parts. Set in the dashboard of an airplane, the device will warn the pilot of engine trouble before he can detect it with his own ears.