Loudest

A giant loudspeaker stood on the roof of a hangar at Mineola, L. I., last week, and radio and sound engineers trooped out to have a look, listen to its monstrous bray. Developed in the Bell Telephone Laboratories, the apparatus resembled a big searchlight. When it and 18 others like it are mounted soon atop a 100-ft. tower, their combined blast will be the loudest sound ever produced by man.

The amplifier assembly will serve Roosevelt Raceway, a pretzel-shaped automobile track on the site of Roosevelt Airport No. 1. From the glass-enclosed studio on the grandstand top announcements will spray over an area half a mile square, can be stepped up, if necessary, to carry a mile. Thus will be eliminated the jumbling ordinarily caused by announcements issuing simultaneously from loudspeakers at different points on a field. Total power consumption is 20,000 watts, enough to lift a ton 7 feet every second.

At the mouth of the amplifiers the intensity of sound will be about 140 decibels. A decibel is an arbitrary unit representing approximately the minimum intensity change which the human ear can detect. Every increase of one decibel multiplies the intensity by 1.25. One hundred and forty decibels is not 40% louder than 100 decibels, but 10,000 times louder. Loudest human shout ever recorded was 86 decibels. Other recorded loudnesses:

Motor truck 102

Motor horn 104

Thunder 106

Pneumatic riveter 109

Airplane 123

Loudest sound in history is believed to be the explosion of the island of Krakatoa in 1883. Physicists estimate the noise of that cataclysm at 190 decibels.

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