This is an idea for an undersea noise generator which may help to locate people lost at sea by day or night. It was produced after I had discussed my idea of the anti-hypothermia lifesaver with my friend - an airline pilot called Arthur.

He has had the idea for some time. He was sure that an under-sea noise generator could be made which could be detected by defence equipment which was originally designed to detect enemy submarines. He did not know how such a device could be made but he was sure that a large number of under-sea listening devices were still in action around the world which could detect and get a bearing on such a noise. He visualised it as a device to help locate pilots who had been forced to parachute into the sea.

The device consists of a noise generator and an inflatable balloon. The noise generator is fitted with propeller blades so that it will rotate as it is raised and lowered in the water by the balloon with the rise and fall of the waves.

Inside the container is a flywheel attached to the container by a rubber band. On the same shaft as the flywheel is a bumpy disc. At the bottom of the container is a lightweight metal beam with a small magnet at either end. The centre of the beam is attached to the centre of a hydro-acoustic diaphragm.

As the waves rise and fall, the container rotates, but the inertia/momentum of the flywheel is such that it will tend to remain still, or rotate in the opposite direction to the container, until the rubber band develops enough torsion to cause it to rotate in the same way as the container. The momentum built up by the flywheel will cause it to keep rotating in the same direction when the rotation of the container reverses. This process will continue indefinitely while there are significant waves. The result is that the flywheel will be rotating in the opposite direction to the container for some of the time or faster or slower than the container for the rest of the time. This will cause the magnets at either end of the beam to be attracted by the bumps as the wheel rotates. This movement is transmitted to the diaphragm and the diaphragm vibrates in step with the bumps.

The sound produced will depend on the bumps on the disc and the relative speeds of the container and the flywheel. The pitch will rise and fall, making what is thought to be a noise which is unlike most natural or man-made under-sea sounds. The frequency range will vary with the number of bumps on the wheel and the rate of rise and fall of the waves and could be from 0 to 9KHz or more.

Located under the container is a tapered cone which is designed to distribute the sound radially.

Whale "songs" can be detected several hundred miles from their sources. It is possible that this device would have a similar range. This noise would be detectable by a hydrophone as fitted to sonobuoys and other devices previously used for defence purposes.

If this device accompanied someone lost at sea, it could be used to help locate the person by day or night.

Copyright (C) W. H. James 14/6/1998
Wilf James,106 Jarden, Letchworth, Herts. SG6 2NZ, UK.
E-mail wilf.james@net.ntl.com.