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Information about TOROID

Published on November 3, 2008

Author: acoustics101


The Toroidal Whistle : The Toroidal Whistle by Rick Weisenberger Background of the Invention : Background of the Invention In the past, whistles were loud but very inefficient devices for producing sound. Part of the problem was that they were designed to operate at high (150 PSI) pressure and also required large flow rates of approx. 100 CFM per inch in diameter. Toroidal whistles still require large flow rates, but operate efficiently at only 15 PSI. A toroidal whistle operates as a very large phased array of conventional cylindrical whistles. The Prototype Test : The Prototype Test Click left mouse button on video to play What is a Toroidal Whistle? : What is a Toroidal Whistle? Plain toroidal whistle : Plain toroidal whistle What is a toroidal whistle? : What is a toroidal whistle? Horn loaded inverted toroidal whistle driver section : Horn loaded inverted toroidal whistle driver section Horn loaded inverted toroidal whistle : Horn loaded inverted toroidal whistle What are the advantages over Sirens? : What are the advantages over Sirens? A siren produces not only the fundamental (operating) frequency, but a rich spectrum of harmonics as well. At close range, these harmonics occur at levels and frequencies most injurious to hearing, however they contribute very little to overall level in the far field, as these frequencies are most attenuated by atmospheric absorption. As a result, sound levels fall off quicker than predicted by the inverse square law alone. Fighting Paradigm Paralysis : Fighting Paradigm Paralysis Since the 1940s, sirens and air horns have replaced whistles as the prime long range sound signal, due to their much higher operating efficiencies. The conversion efficiency of a plain toroidal whistle compares favorably to that of an air horn, while the efficiency of a horn loaded inverted toroidal whistle compares with that of a siren or even that of the new high powered electronic warning devices. Applications for Toroidal Whistles : Applications for Toroidal Whistles A toroidal whistle is by nature a very efficient high power sound signal, as it operates as a large phased array of conventional cylindrical (steam) whistles, but at approx. 1/10 the pressure. At a pressure of only 15 PSI a 20” diam. Toroidal whistle produces an SPL of 125 dB @ 100 ft. A horn loaded inverted toroidal whistle uses 25% less airflow, but can produce an SPL of 135 dB @ 100 ft. Finally-A Warning that will reach the Public : Finally-A Warning that will reach the Public As we all know, although the largest sirens are near field rated as high as 135 dB @ 100 ft. most warning sirens simply cannot be heard indoors at a great distance. This is due to much of their output at upper harmonics trying to heat the air around them. A 135 dB rated siren is down to approx 70 dB at under 10,000 ft. The 125 dB @ 100 ft. toroidal whistle prototype was still producing 76 dB at 2 miles! Introduction to the Market : Introduction to the Market The next step is to introduce a working model of the horn loaded inverted toroidal whistle to the public by having one built and installed where it can be demonstrated. Its far field performance will amaze any DES official familiar with the performance limitations inherent in the present system of warning sirens. Slide 14: For further information on the technology behind the toroidal whistle visit my webpage at

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