CA1314089C

CA1314089C - Pressure compensated communication system

Info

Publication number: CA1314089C
Application number: CA000581692A
Authority: CA
Inventors: David S. Fincher
Original assignee: Divelink Pty Ltd
Current assignee: Divelink Pty Ltd
Priority date: 1987-10-30
Filing date: 1988-10-28
Publication date: 1993-03-02
Anticipated expiration: 2010-03-02
Also published as: GB8825303D0; GB2212027A; US4926398A; GB2212027B; AU616689B2; AU2451188A

Abstract

ABSTRACT OF THE DISCLOSURE

The present invention provides a pressure compensated communication system having at least one audio transducer, the pressure compensated communication system comprising a fluid tight housing for the or each audio transducer, the or each housing having a corresponding one of the or each of the audio transducers located therein and having an orifice coupled to a pressure compensation means, the pressure compensation means connected to the or each orifice and to a continuous supply of gas at a pressure equal to or slightly greater than the pressure of liquid surrounding the housing.

Description

- 1 13140~9 TI TLE
"PRESSURE COMPENSATED COMMUNICATION SYSTEM"
DESCRIPTION
The present invention relates to a pxessure cvmpensated communication system particularly envisaged for use at sub-atmospheri~ or super atmospheric pressures.
FIELD OF THE IN~ENTION
In general, audio transducers, such as microphones and loud speaXers, for communication systems are constructed to operate at normal atmospherlc pressures. However, such audio transducers ~ave been used at super atmospheric pressures such as in underwater communicatlon systems for divers.
In such cases the audio transducers must be protected from contact with water. Protection 1~ usually achieved by hermetically encaslng the aud~o transducers ln epoxy r~sin.
Xowever, the epoxy resin substantia~ly reduces the flow of acoustic energy into and out of the audio transducer, resulting in loss o~ sound volume and distortlon of the transmitted and received sound.
Also, the audio transducer, in use, has an lnternal pressure set at atmospher~c pressure and an o~tside pressure which increases at a rate of about 100 kpascals o~ every 10 metres below the surface of the ocean. The resultant pressure imbalance pressurizes the audio transducer and reduces its sensitivlt~ ~o incldent acoustlc energy. With continued lncrease in the pressure lmbalance the audio transducer usually experiences mechanical fallure.
It is known to use bone type microphones and loudspeaXers ~. ;

~ 2 -encased in epoxy resin to shleld same from ingress of water but the inside remains at normal atmospheric pressure and so the acoustic volume decreases wlth depth under water.
~owever, these micropho~es and loudspeakers have very low sensltivity, poor frequenc~ response, low acoustic volume -and therefore not well suited for underwater communica~ion.
It ls also known to house conventional type audio transducers in hermetically sealed containers with a diaphragm in pressured communicatlon with its surroundings.
In use, super at~ospheric pressures, such as experienced under water, deform the diaphragm and pressurize the container so that the audio transducer experiences super atmospheric pressures ln balance, that is from within and without.
15 The general problem of such prior art arran~ements is that the amount of compensatlon achievable is ~imited by the flexibill~y of the diaphragm in the container. So a depth will be reached past whlch no compensation will occur.
Also, such diaphragms are prone to fa~lure by perishing or puncturing and otherwlse being handled roughly. In such case since the inslde of the container is never at a higher pressure than that o the surrsundings wa~er enters the container, displaces the alr and ~estro~s the audio transducer.
~5 SUMMARY OF THE INVENTION
The present inve~t~on pro~ides a pressure compensated communicatlon system haYing audio transducers ~ith pressure compensation means in communication with a continuous supply of compressed gas ~or sub-atmospheric pressure ~as) 1 31 40~q substantlally eliminate pressure imbalances between the operating pressure of the audlo transducer and the pressure of the surrounding enviro~ment.
In accordance with the present invention there is provided a S pressure compensated communication system having at least ~
one audio transducer, the pressure compensated communlcation s~stem compris~ng a fluld tlght housing for the or each audio transducer, the or each housing having a aorresponding one of the or each of the audio transducers loca~ed th~rein and having an orifice coupled to a pressuxe compensation means, the pressure compensation means connected to the or each oriflce and to a continuous supply of gas at a pressure equal to or sllghtly ~reater than the pressure of liquld surrounding the housing.
Preferably, the pressure compensation means interconnects each of the audlo transducers.
In the context o~ the present invention "gas" includes air and gases such as helium often used in deep sea diving and the like.
Also, in the context of the present lnvention "continuous"
in relatlon to supply o~ gas means persisting ~or as long as gas ~s s~pplted to the divers using the apparatus o~ the invention.
The present lnvsntion will hereinafter be described wi~h partlcular reference to operation under the oaean sur~ace and at super atmospheric pressures, although i~ ~s to be understood that it could be operated at sub atmosph~ric pressures.
The present invention will also hereinafter be desarlbed 13~40~9 with particular reference to audio transducers belng m1crophones and loudspeakers.

BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will now be described by way of example with reference to the accompanying drawings, in which:-Fi~ure 1 is a cross sectional view of a housing of a pressure compensated communication system in accordance with the present invention haviny a loudspeaker in it;
Flgure 2 is a cross sec~ional view of the housing o~ Figure 1 having a microphone ln it; and Figure 3 ls a schematic view of the pressure compensated communlcation system of the present inventlon.
DESCRIPTION OF THE INVENTION
In Figure 3 there ls shown one exemplary embodiment of a pressure compensated communication system 10 in accordance wlth the present invention. The system 10 comprises three ~luid tighk housings 12, 14 a~d 16 each of a simllar construction.
Preferably the housings 12, 12, 16 are relatively rigid in construction and substantlally free from resillent deformation. That ls any resilient deformation that the housings 12, 14, 16 may experience does not substantially lncrease th~ pressure lnside the housings ~2, 14, 1~ so as to provide pressure compensation. It is however, to be understood, that the hous~ngs ~2, 14, 16 could be relatively flexi~le such that external pressure could create compensation by deforming the housings 12, 14, 16 to incxease the pressure therein. However, such characterist~c 1 31 40~q ls of no benefit to the present invention and represents a superfluous feature, not requlred by the present lnvention.
The hou~in~s 12, 14 and 16 each comprise a cha~ber 18 formed o~ a base 20 with an externally threaded lip 22 and an apertured cap 24 with an internally threaded skirt 26 as '-shown in ~igures 1 and 2. The sklrt 26 of the cap 24 is dimensioned to threadedly engage with the lip 22 of the base 20.
The cap 24 has a hole 28 disposed to correspond with the chamber 18.
~yplcally, the base 20 and the cap 24 are made form plastics material, such as, nylon.
The cap 24 also comprises an "O" ring seal 30 seated ~nto it. The seal 30 is disposed to mate with a bevel 31 formed in the llp 22 to create a fluid tight connectlon between the cap 24 and the base 20 when same are threaded to~ether.
Such threading results in a compression o~ the "O" ring seal 30 between the bevel 31 and tXe ca~ 24. Typically, the bevel 31 1~ at about 45 to the thread of the llp 22.
The housings 12, 14 and 16 each also comprise a membrane 32 formed of flexlble and fluid tight material such as for example material available under the Trade Mark ~YLAR or the li~e. The membrane 32 is dimensioned to fit between the "O"
ring seal 30 and the cap 24 to close off the hole 28 to prevent ~luid such as water from entering the chamher 18 via the hole 28.
The membrane 32 preferably ls capable of deflection in sympathy with acoustic energy incident upon it so as to transmit the acoustic energy through lt.

1 31 40~9 The cavity 18 is dimensioned to receive an audio transducer such as a loud speaker 34 as shown in Figure 1 or a microphone insert 36 as shown in Figure 2. The lip 22 has a seat 33 dimensioned to loosely receive a cone frame of the audio 05 transducer 34, 36. The loose fit is such as to allow passa~e of some air or gas from the chamber 18 to the membrane 32 to equalize the pressure across the audio transducer 34, 36.
The audio transducer 34 or 36 is preferably loosely clamped in place in the housing 12, 14 or 16 by the threaded engagement of the cap 24 to the base 20. The audio transducer 34 or 36 is thereby disposed adjacent the membrane 32.
The housings 12, 14 and 16 each also comprise an orifice 38 and 40 respectively. The orifice 38 carried electrical wires 42 which are connected to the loud speaker 34 and the orifice 40 carries electrical wires 44 which are connected to the microphone insert 36.
The orifices 38 and 40 are in fluidlc communication with the respective chambers 18 and therefore the respective audio transducers 34 and 36.
It is to be noted that if the MYLAR (trade mark) membrane 32 is subjected to a large pressure gradient it will be deflected into the chamber 18, crushing the audio transducer and tearing, thus allowing water into the chamber 18.
Accordingly, it is essential to equalize the pressure in the chamber 18 and adjacent the inside of the membrane 32 with that of the liquid or gas in the surroundings.
The pressure compensated communication system 10 also ;1 . `~

, 13140~9 ~ 7 -comprlses a pressure compensation means conveniently in the form of a plurality of hoses 46, 48 and 50 connected between the oriflces 38 and 40, as shown in ~igure 3, so as to maintain the chambers 18 of each of the housings 12, 14 and 16 in fluidic communlcation so that the pressure within each of the houslngs 12, 14 and 16 is maintained substantially the same. The hose 50 connects the houslngs 14 and 16 together and the hose 48 connects the housings 12 and 14 together.
The system 10 of Flgure 3 schematlcally shows two orifices in each of the the housings 12 and 14 but lt ls to be understood that one orifice could be used with a T piece to ~oin the hoses 46 to 48 and 48 to 50 and to the ori~ices 38 of the housings 12 and 14.
1~ The hose 46 has a free end 52 terminating in a relatively small aperture 54. That is the aperture 54 is small relative to the diameter of the hose 46. The ree end 52 is arranged to be coupled to a continuous suppl~ of ~luid, such as a supply of air, which fluid is at a pressure substantially equal or slightly greater than (i.e. 3 kpa greater than~ the pressure of the environment surroundinq of the houslngs 12, 14 and 16.
In one embodiment~ for communication for underwater divers the hose 46 has its free end 52 connected to or mounted into a face mask used by the diver, which face mask is connected to a conti~uous supply o pressurized air, and sometimes other gases..
The face mas~ is 1ntended to be of the full face type in whlch the diver does not have a mouth piece supplying alr 1 31 40~q into his/her mouth but a regulator supplying alr into the mask. Such full face type masks generally operate at about 3kPa above the pressure of the surroundi~g water to reducQ
the likelihood of ingress of water ~nto the mas~. Air is generally supplied by an air hose from the surface of ~he ocean or from an aqualung air tanX to the face mask.
~he aperture 54 is preferably relatively small to reduce the likelihood of ingress of water or molsture into the housings 12, 14 or 16.
The wires 42 and ~4 are laid inside the tubes 48 and 50 to the housing 14 whereat they connect together and pass out o~
the housing 14 via wires 56. The wires 56 run in a wate~tight cable 58 to an amplifier or the like at a location either remote from the dlver, suc~ as at the ocean sur~ace, or to a wlreless transceiver carried by or upon the diver.
It ls envisaged that the houslngs 12 and ~4 could hav~ a diameter of about 70mm and a thickness of about 35mm and the housing 16 could have a diameter of about 42mm and a thlckness of about 20mm.
It is envisaged that the loudspeakers 34 and the microphone 36 all be wired in parallel connection by the wires 42 and 44, for us~ in a simple communication system. Alternatively the m~crophone 3~ could be wired separately to the loudspea~ers 34, resulting in ~our airs 56 for use ln a duplex cor~unicatlon system.
It ls also envisaged that the orifices 38 an~ 40 could be formed ~y spigots threaded or welded into holes in the housings 12, 14, 16.

~ 31 40~39 g It iq also envisaged that the microphone insert 36 could be a mlniature loudspeaker.
In use, the housings 12 and 14 are located, ln the present embodiment, ln the divers full face rnas~ ad~acent his/her ears. Depending on the type of mask the housings 12 and 14 may be immersed in water. At such location the housings 12 ~nd 14 seal the loudspeakers 34 from the water and the membrane 32 allows passage o~ acoustlc ener~y from the loudspeaker 34 out of the hous~ng 12 and i4 to the divers ears.
The housing 16 ls located in the divers full face mask adjacent the persons mouth so as to receive acoustic energy when the person speaks. The housing 16 may be ormed into the mask with part of the housing immersed ln water. The acoustic energy lnciden~ on the housing is allowed to pass into the chamber 18 throu~h the membrane 32. The acoustic energy is converted to electrical energy by the microphone insert 36 and output to the wires 44 and sent along the wires 56 for amplification and the like at the ocean surface, such as on a boat used ~o supply air to the diver or at the wireless transceiver carxied b~ or upon the diver. ~ence, the diver can communicate with persons on the boat or to other divers.
Electrlcal s~gnals from the ampllfier are transmltted to the loudspeaXers 34 via the wires 56 for production of acoustic energy and communication of volce messages to the diver.
The hose 46 has its free end 52 flxed to the full face mask so that ai~ in the mask ~asses to the chambers 18 in the event ~hat the chambers are at a lower pressur~ than the pressuxe of the mask and air passes from the chambers 18 to the mask in the reverse case. Accordlngly, the loudspeakers 34 and the micropho~e lnsert 36 are not operated at a substantlal pressure gradlent and so operate normally. That ls the pressure gradient wlll usually be no more than about.
3kPa, with the air pressure being the greater.
As the divex descends the air pressure in the mask ls increa~ed to compensate the dlver for the increase ln water pressure. Conseguently the air pressure in the ahambers 18 is also increased by pressure o~ air through the hole 54.
The reverse occurs when the diver ascends. Thus, the apparatus 10 does not consume air.
In the event that the apparatus 10 develops a leak and is no longer fluid tight wlth respect to the surrounding ~5 environmen~, a small amount of compressed alr will escape since the air pressure is about 3kPa above the water pressure. Consequently in~ress o water in such aircumstance~ is resisted.
The present inven~on has the benefit of relatively undistorted audio communlcation and attainment of reasonable sound pressure levels independant of the pressure of the surrounding environment in which the audio tran~d~cers 34 and 36 opera~e~
Also, since the loudspea~ers 34 are housed ln the housings 12 and 14 the base frequency response and hence clarlty is improved. In the absence of the housings 12, 14, 16 apart from problems o~ pressure gradients, sound pressure waves from behind the loudspea~ers 34 interaat with those created in front of the loudspeaXer and serve to reduce base 1 3 1 40gq response, clarity and fidelity as a whole.
Further, the audlo transducers 34 and 36 remain relatlvely dry.
Still urther, due to the housin~s 12, 14 and 16 the acoustic volume is much greater than would otherwise be the-case.
Still further, due to the pressure compensation the f~delity o~ t~e audio transducers 34, 36 is malntained lndependent o~
operating depth in water.
Still further, by virtue o~ the posltive, but small pressure gradient developed the apparatus 10 is substantially immune to ingress of water even if a fluid leak develops.
It is to be noted that the apparatus 10 fill up with water from withln the mask only if there was a fal~ure in the air supply to the masX and under such conditions the diver would drown.
It ls also to be noted that prior art systems have striven for totally closed systems of operation whllst the apparatus 10 of the present lnventlon is an open system as far a~ alr communication is concerned and rell~s on the divers mask to create a closed system as far as water ls concerned.
It is also be noted that by virtue of Lts construction the apparatus 10 is servlceable.
It is envisaged that polycarbonate cone loudspeakers 34 be used in the lnvention so as to be less prone to damage by water vapour which may collect in the chambers 18.
It is also envisaged that the pressure in the hous~ngs 12, 14, 16 could be between 1 to to kPa greater than their surroundings.

~ 1314089 Modifications and variation~ such as would be apparent to a s~illed addressee are deemed withln the scope of the present invention.

Claims

1. A pressure compensated system to be submerged in a surrounding liquid and having at least one audio transducer, the pressure compensated system comprising a fluid tight housing for containing the audio transducer, the housing having an orifice pressure compensation means connected to the orifice for receiving a continuous supply of gas at a pressure equal to or slightly greater than the pressure of liquid surrounding the housing, the housing comprising a base of relatively inflexible material having formed in the base a chamber to receive the audio transducer, an apertured cap fixable to the base, a fluid tight membrane disposed between the base and the cap to overly the chamber and in communication with the surrounding liquid at a first surface and in communication with the supply of gas at a second surface, and sealing means disposed to seal the membrane to the base for preventing the surrounding liquid from coming into the chamber.

2. A pressure compensated system according to claim 1, in which the pressure compensation means comprises a first hose connected between the housing and a second housing containing a second audio transducer to maintain the first and second housing in fluid communication therewith and a second hose adapted to be connected to the continuous supply of gas.

3. A pressure compensated system according to claim 2, in which the second hose is adapted to be fixed in fluid communication with an underwater divers face mask.

4. A pressure compensated system according to claim 3, comprising electrical cables interconnected to the audio transducer, the electrical cables being disposed within the hoses between two of the audio transducers.

5. A pressure compensated system according to claims 1, 2, or 3 or 4 in which the base comprises a lip for attachment of the cap, the lip having an outside bevel, and the sealing means comprising an "O" ring seal, the "O ring seal being disposed between the bevel and the cap, the bevel and the cap co-operating to compress the "O" ring seal into sealing engagement between them.

6. A pressure compensated system according to claim 3, in which the pressure compensation means maintains the pressure of gas within each housing at between 1 to 10kpa above the pressure of the surrounding liquid.

7. A pressure compensated communication system to be submerged in a surrounding liquid and having at least two audio transducers, the pressure compensated communication system comprising a first fluid tight housing for containing a first audio transducer, a second fluid tight housing for containing a second audio transducer, the first and second housings having an orifice, pressure compensation means for receiving a continuous supply of gas at a pressure equal to or slightly greater than the pressure of surrounding liquid, the pressure compensation means comprising a hose connected between the orifice of the first housing and the orifice of the second housing to maintain the first housing and the second housing in fluid communication and a second hose adapted to be connected to the continuous supply of gas.

8. A pressure compensated communication system according to claim 7, in which the housing comprises a base of relatively inflexible material having formed in it a chamber to receive the audio transducer, an apertured cap fixable to the base, and a fluid tight membrane disposed between the base and the cap to overly the chamber and in communication with the surrounding liquid at a first surface and in communication with the supply of gas at a second surface, and sealing means disposed to seal the membrane to the base for preventing the surrounding liquid into the chamber.

9. A pressure compensated system to be submerged in a surrounding medium having at least one audio transducer, the pressure compensated system comprising a medium tight housing for containing the audio transducer, the housing having an orifice, pressure compensation means connected to the orifice for receiving a continuous supply of pressurized medium at pressure equal to or slightly greater than the pressure of the surrounding medium of the housing, the housing comprising a base of relatively inflexible material having formed in it a chamber to receive the audio transducer, an apertured cap fixable to the base, and a medium tight membrane disposed between the base and the cap to overly the chamber and in communication with the surrounding medium at a first surface and in communication with the supply of pressurized medium at a second surface, and sealing means disposed to seal the membrane to the base far preventing the surrounding medium from coming into the chamber.

10. A pressure compensated system according to claim 9, in which the pressure compensation means comprises a first hose connected between the housing and a second housing containing a second audio transducer to maintain same in fluid communication therewith and a second hose adapted to be connected to the continuous supply of pressurized medium.