Vocal Communication Snorkel

This invention relates generally to underwater communication devices and specifically to a simple, low cost, passive vocal communication snorkel. The art has long attempted to develop a passive, voice-powered communication device for enabling underwater communication. These devices were intended for use by scuba divers who carry tanks of compressed air for breathing. The stream of exhaust air bubbles, emitted from the swimmer's regulator, creates an ambient noise problem that renders intelligible underwater communication very difficult indeed.

A snorkeler, however, generally swims (or floats) just beneath the surface of the water and breathes through a breather tube that extends above the surface of the water. The breather tube is fitted to a mouthpiece that is held in the snorkeler's mouth. Since there is no stream of air bubbles being emitted, the ambient noise is much less of a problem. Yet, to date, there has been no successful passive underwater voice communication snorkel developed.

The characteristic impedance of water is 3600 times higher than that of air and therefore the communication of sound vibrations across an air water interface involves significant losses. The wavelength of sound in water is about 4.4 times greater than in air, hence a diaphragm size of 3 inch diameter, for example, is rather small to efficiently radiate voice frequencies in water. Consequently, such a diaphragm will exhibit substantial mass loading and reduced radiation impedance.

The base frequencies of the vocal chords, i.e. 100-200 Hertz, are normally suppressed when speaking in an air medium because the mouth area is too small to radiate them efficiently. These frequencies experience an increase of from 20-30 dB when speaking into a small enclosure such as a mask, a tube or the like. Additionally, a person's cheeks, throat and chest vibrate with low frequency sound, which is communicated to the water, forming a mass of unintelligible sound. This severely affects the intelligibility of the sound and is a major problem in developing a successful passive voice communication snorkel.

The voice communication snorkel of the invention solves many of the problems enunciated above. The preferred embodiment uses a pair of molded 0.008-0.014 inches thick, spherically shaped, polyester diaphragms that are mounted with an inward curve to decrease the volume of the cavity in the hollow snorkel body and to minimize the possibility of mechanical damage. The in-air resonance of the diaphragms are in the range of 3000 to 6000 Hertz. The mass loading of the water reduces their in-water resonance frequency to 1500-3000 Hertz. At the resonance frequency, the mass loading of the diaphragms is canceled by the stiffness of the diaphragm, and sound vibrations are coupled into the water. This supplies the higher voice frequencies which are necessary for intelligibility. While a two diaphragm snorkel is the preferred embodiment, a single diaphragm model will work, although with poorer intelligibility. Three or more diaphragms may be used with somewhat better results. In all multiple diaphragm cases, the individual diaphragms should be tuned to resonate at slightly different, overlapping frequencies to maximize the efficiency in covering said frequency range.

A major feature of the inventive snorkel is the mouthpiece containing a passageway that functions as a pair of "rubber lips", allowing air to be inhaled easily and yet providing for articulation of the exhaled air. This passageway is controlled by the lips of the snorkeler. A readily collapsible bubble is formed in the throat of the mouthpiece for engagement by the lower lip of a snorkeler. The bubble may be collapsed by minimal pressure from the snorkeler's lower lip to close the throat and help articulate plosive sounds.

A principal object of the invention is to provide a novel voice communication snorkel.

Another object of the invention is to provide a passive means for enabling short distance, intelligible underwater communication between snorkelers.

A further object of the invention is to provide an improved snorkel breathing apparatus.

These and other objects and advantages of the invention will be apparent upon reading the following description in conjunction with the drawings, in which:

FIG. 1 is a plan view of a snorkel constructed in accordance with the invention;

FIG. 2 is a sectional side view of the snorkel of FIG. 1; and

FIG. 3 is a top view of the snorkel of FIG. 1.

Referring to FIGS. 1-3, the snorkel of the invention includes a hollow, generally disk shaped body 10 with a pair of inwardly curved hemispherical diaphragms 12 and 30 affixed to opposite sides thereof. The volume between the inwardly curved diaphragms 12 and 30 comprises an air chamber to which is coupled a conventional breathing tube 16 that is adapted to extend above the surface of the water to enable the user to inhale and exhale air. A mouthpiece 14 is coupled to body 10 and defines an elongated, relatively narrow passageway or throat 28 that communicates with the interior of body 10. A relatively large flange fits between the user's front teeth and the inside of the lips, securing the mouthpiece in place. A pair of bits 20 and 22 are adapted to be held, when necessary, between the clenched teeth of the snorkeler with the snorkeler's lips engulfing the mouthpiece 14 and engaging the entrance of passageway 28. Pressure from the snorkeler's lips enables the interior of passageway 28 to be collapsed to substantially close off the air communication between the mouthpiece and body 10 for articulating plosive sounds. Diaphragms 12 and 30 may be sealed in body 10 by any well known watertight sealing technique, with a seal ring 24 being shown. The body may be made of metal or any other rigid material. In a practical embodiment, the body is of molded plastic with the diaphragms being held in position by means of seal rings 24 which may be secured by cementing, ultrasonic welding, or the like. A purge valve 25 extends from the lower end of the body 10 and assists a snorkeler in clearing the body of water, as required. The purge valve 25, as is well known, is a one way flapper valve that is lightly loaded.

As best seen in FIG. 3, the mouthpiece has formed therein a pair of flexible lips 26 at the entrance of passageway 28. These flexible lips are collapsible by pressure from the lips of a snorkeler when articulating sounds, such as plosive sounds. As seen in FIG. 2, a bubble 18 is formed in one side of passageway 28 for facilitating rapid closure of the lips 26 with minimal effort of the snorkeler. The bubble 18 will "pop" inside out with the application of mild force from the lower lip of the snorkeler to close the air passage. This facilitates fairly normal speech movements which are impeded if large lip forces are required. It will be appreciated that the need to breathe imposes substantial limitations on the minimal throat and lip opening and poses the additional requirement that the lips be biased to an open position. Thus the provision of the bubble 18 significantly reduces the force required to close the flexible lips for forming plosive sounds without compromising the "open bias" of the flexible lips.

It will be further appreciated by those skilled in the art that the invention introduces into the water higher frequency sounds to balance the lower and mid frequency sounds that are already present. As mentioned, these latter sounds are readily coupled to the water from the snorkel mouthpiece, body and tube (and from the snorkeler's throat, chest, etc.) and create the intelligibility problems discussed above.

By supplying the higher frequency sounds, the masking effect of the introduction of the glottal and low frequencies is balanced to aid in communicating intelligible speech.

What has been described is a novel underwater voice communication snorkel that solves many of the problems of the prior art devices. It is recognized that numerous changes in the described embodiment of the invention will be apparent to those skilled in the art without departing from its true spirit and scope. The invention is to be limited only as defined in the claims.