The use of Self Contained Underwater Breathing Apparatus by divers in carrying out a number of operations has greatly increased in recent years. Such operations may include spear fishing, photography and simple sightseeing as recreational activities. In other operations, divers can repair ship hulls, submerged machinery, piers, and pilings, as well as assist in petroleum drilling and extraction, laying and inspecting pipelines, and in placement of heavy underwater valves in sealed installations. Still other operations include harvesting of abalone, kelp and sea urchins commercially.
In all of the foregoing activities, it is common practice for divers to work in pairs. Thus, working together in a hazardous environment, they have a great need to be able to communicate observations, precautions and intentions one to the other.
In an effort to provide convenient underwater communication between divers, various underwater speaking devices have been proposed. Basically, these devices fall into two groups: first, mechanical devices wherein acoustical sound energy generated by the diver's voice is simply mechanically transferred to the surrounding water; second, electronic types in which either interconnecting wires, ultra sound electronically generated or electromagnetic radiation is utilized to carry the communication energy between transducers.
Unfortunately, such underwater speaking devices as have been provided to this date have not proved particularly satisfactory whether of the mechanical or electronic type. In the case of presently available mechanical speaking devices, there is an enormous loss in acoustic energy because of reflection when the energy transmission is attempted from air vibrations to vibrations in the water without means to match impedance. No prior art has been discovered which affords said matching. Thus a practical range for speaking with such mechanical devices has not, as a practical matter, been realizable. The electronic devices, on the other hand, while operable are relatively expensive and further are not often clear and distinct.
In general, it would be more desirable to provide a wholly mechanical type of underwater speaking device not only from the standpoint of economics but because if such a device could be provided to generate sufficient sound energy in the water, there is minimal loss in fidelity as compared to the electronic systems.