Page:Popular Mechanics 1928 11.pdf/38

 



French experts have recently introduced a camera that takes pictures of the inside of pearls so that the genuine may be told from the imitation. Detailed views of the interior structure, and other points that are impossible to detect with the unaided eye, are said to be clearly revealed so that successful passing of the false for the gennine is not likely to occur after an examination with the instrument.

 

Further interesting experiments with inaudible sound waves have been performed recently by Alfred L. Loomis, who causes a quartz crystal to produce vibrations at the rate of two and one-half million per second, called "death whispers," because they kill small organisms in water. In earlier experiments, he produced vibrations at the rate of three-quarters of a million per second. The more recent effects have been obtained with a tiny slab of quartz, less than an inch long, about three-eighths of an inch wide and one-sixteenth of an inch thick. Its high rate of vibration is partly due to its smaller size as compared with the other crystal. and to the more rapidly oscillating electric current to which it is submitted to cause vibrations. Plant and animal cells were killed by the violent stirring of their contents. The cell walls of the plants were not broken, as they were evidently too tough and strong, but the contents were seen to be swirled into a disorganized mass by the action of the weird whispers of death.

 

Listening to radio programs through loud speakers, as many as 250 of them a day, is the task of Martin T. Olsen, a veteran in one of the most highly specialized activities in the world. He is a tone tester. Just as the tea taster's sense of taste has been developed to a point where he can detect the slightest difference in blend, so Olsen's ears can distinguish the least variation in pitch. The average person can tell the difference in tones or notes up to about 5,000 or 6,000 frequencies per second, scientists say, but Olsen, in a competitive test, demonstrated that he was able to distinguish notes at frequencies of over 10,000 cycles per second. During a broadcast program, he can usually tell if distortion or extraneous noise is the fault of the microphone, is in the station studio or if the interfering noise or faulty tone is caused by the set itself, and if so, where the trouble lies. His chief business is to listen to the loud speakers manufactured by a radio company to determine if they are up to the standard of the master model in tone and pitch. If they are not, Olsen's keen sense of hearing aids in locating the difficulty.



