US3813687A

US3813687A - Instant replay helium speech unscrambler using slowed tape for correction

Info

Publication number: US3813687A
Application number: US00310628A
Authority: US
Inventors: F Geil
Original assignee: US Department of Navy
Current assignee: US Department of Navy
Priority date: 1972-11-29
Filing date: 1972-11-29
Publication date: 1974-05-28
Anticipated expiration: 1991-05-28

Abstract

The helium speech processing device employs a cassette tape recording system which makes a sentence-by-sentence or phrase-byphrase recording of the speech of a helium gas breathing diver and replays this recording at a reduced speed to provide increased intelligibility. The speed of replay is controllable by the diver and automatically in response to a depth sensing mechanism as well as a speed range control mechanism which is pre-set in dependence upon a particular gas mixture that the user is breathing.

Description

United States Patent 91 Geil [451 May 28, 1974 [54] INSTANT REPLAY HELIUM SPEECH 3,584,158 6/1971 Jefferies 179/100.2 T 3,588,359 6/1971 Cribb 179/1 VC UNSCRAMBLER USING SLOWED TAPE FOR CORRECTION Fred G. Geil, San Diego, Calif.

Filed: Nov. 29, 1972 Appl. No.: 310,628

Inventor:

US. Cl. 360/8, 179/1 UW, 179/1 VC, l79/100.l VC, 360/73, 360/7 Int. CL... Gllb 15/44, G1 lb 15/10, Gllb 1/04 Field of Searchl79/l00.2 K, 100.2 T, 100.2 R,

l79/l00.1 VC, l00.l TC, 1 SA, 1 UW, 1 VC I References Cited UNITED STATES PATENTS OTHER PUBLICATIONS I-Iolywell and Harvey, Helium Speech, The Journal of the Acoustical Society of America, Vol. 36, No. 1, Jan. 1964, pages 210-21 1.

Primary ExaminerBernard Konick Assistant Examiner-A1fred H. Eddleman Attorney, Agent, or FirmRichard S. Sciascia; Ervin F. Johnston; William T. Skeer [5 7 ABSTRACT The helium speech processing device employs a cassette tape recording system which makes a sentenceby-sentence or phrase-by-phrase recording of the speech of a helium gas breathing diver and replays this recording at a reduced speed to provide increased intelligibility. The speed of replay is controllable by the diver and automatically in response to a depth sensing mechanism as well as a speed range control mechanism which is pre-set in dependence upon a particular gas mixture that the user is breathing.

9 Claims, 5 Drawing Figures PAYENTEDIAY 28 m4 SHEET 1 BF 2 FIGK PATENTEDmzs I974 3813,1687

tw REC PB TO E COMMUNICATION EQUIPMENT EOUALIZA TION EQUALIZATION V MOFF MOTOR 0N CONTROL PLAY v MOTOR 37 r V 40 A ON OFF MOTOR F- "l CONTROL I W (REC) DEPTH 42 sE/vsOR -E as Y 21 i REOORO GAS MOTOR l MIXTURE I 43 1 SELECT A FIGS V 1 INSTANT REPLAY HELIUMSPEECH UNSCRAMBLER USING SLOWED TAPE FOR CORRECTION STATEMENT OF GOVERNMENT INTEREST The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

FIELD OF THE INVENTION This invention pertains to the field of voice communications. More particularly, this invention pertains to communication between a person breathing a lowdensity gas mixture and others at spaced locations therefrom. In still greater particularity, the invention pertains to a communication system employing a tape recorder playback mechanism in which the voice of the person breathing a low density gas mixture is recorded at a first speed and replayed at a slower speed. By way of further description, but notby way of limitation thereto, the invention pertains to a voice communications system between a diver breathing a heliumoxygen mixture and a person on the surface of the water.

DESCRIPTION OF THE PRIOR ART To avoid physical and psychological problems inherent with the breathing of gas mixtures containing nitrogen at high ambient pressures, divers working in the ocean depths breath a helium-oxygen mixture. Although such a gas mixture prevents the physical and psychological problems encountered when a gas mixture contains nitrogen, an unfortunate side result of this breathing mixture is a highly distorted speech. This speech distortion is due to the lower density of the breathing gas mixture and, hence, dependent upon the pressure and the concentration of the helium gas in the breathing gas mixture. This distortion is characterized by having the formant, or harmonic, frequencies being multiplied upwards by a factor which is dependent upon this pressure and concentration of helium. As a result, the speech of a diver working at depths of f) feet and below is so altered that, for practical purposes,

it is unintelligible without an unscrambling system being employed.

Although a variety of speech unscrambling systems are known in the prior art, they may be classified into three basic types; the heterodyne type, the rotary -head asnet typ,. d digital Signal P FEQ iQ ty equencies. Although this technique has a certain limited application, the results are still unsatisfactory for good intelligibility. This is largely due to the fact that the original frequency distortion resulted in a multiplication of frequencies and the subtraction of a given fre-! quency can only approximate a proper distortion cor-;

rection over a very limited frequency band. Intelligibility over the entire speech spectrum and at a plurality of working depths is therefore unsatisfactory with devices using this technique.

The second technique employs a magnetic recording having a playback head mechanism which comprises a plurality of heads mounted upon a rotary carrier which are rotated as the tape passes by the playback head such that the frequency is substracted and bits of the original recording are removed from the recorded signal. This arrangement has the advantage of permitting nearly simultaneous transmission of the frequency modified and chopped speech with the actual spoken word or, in other words, a real time" transmission of the message is affected. In some applications. this real time capability is quite important and compensates for any other faults which may be presented by this system.

Among the disadvantages of the rotary head technique is the fraility of the rotary head mechanism, the difficulty in making slipring or commutor contact with rotary heads, and the excessive wear of the heads caused by the oxide coating of the recording medium. Another disadvantage is that the system requires considerable mass and weight in order to avoid acceleration caused distortion from afflicting the magnetic recordings speed and the rotational speed of the playback heads.

The last category of prior art signal processors capable of unscrambling the helium-oxygen scrambled speech is the digital signal processing system. This system approximates the results of the rotary head technique without the mechanical rotation from a recording head or the magnetic recording of the processed signal. That is, the speech signal to be unscrambled is sorted by an electronic scanning system known as wave form sampling is stored and reassembled. This equipment, because of its electronic complexity is quite bulky and expensive.

Because of the bulk and expense of the rotary head equipment and the digital processing equipment, such equipment is usually stored aboard the surface vessel or listening point. Such a physical location demands that the individual divers be connected to the fixed point by either a fixed wire or another appropriate communication link. While this arrangement is satisfactory for some operations, it does not readily permit two divers working beneaththe surface to converse with one another or a plurality of diverse to converse with a fixed The invention overcomes these problems by employing a compact recorder method which may be inserted in-line with the existing communication system in use. The wearer of the full face mask speaks his message in a normal conversational tone into a microphone po'sitioned in his face mask. The speech message is recorded and, at the end of the recorded message, is replayed at a different rate of speed. The replay rate may be controlled by the wearer of the face mask by means of a tongue operated speed control as well as an automatic depth sensing circuit. Additionally, the speed of the playback may be adjusted over a wider range of linear speeds by means of a suitable control which, for example, may be a variable impedance connected to the motor speed control circuit. An automatic switch stops the action of the playback motor when the length of tape upon which the original message was recorded has been played.

STATEMENT OF THE OBJECTS OF INVENTION It is accordingly an object of this invention to provide an improved speech processing device.

Another object of this invention is to provide a speech processing circuit employing magnetic recording techniques.

A further object of the invention is to provide a speech processing circuit having the provision of aural feedbackv Another object of the invention is to provide a speech processing circuit which rhay be carried by individual wearers.

Another object of the present invention is to provide a speech processing system having a minimum of controls which are simple to operate.

Another object of the present invention is to provide a speech processing system which is compatible with existing communication equipment.

A still further object of the present invention is to provide a speech processing system which will make intelligible the speech patterns of a user breathing helium-oxygen gas mixtures.

These and other objects of the invention will become more readily apparent from the ensuing specification when taken with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevational view showing a diver using the speech processing equipment of the invention.

FIG. 2 is a front elevational view of a diver showing the placement of the component parts of the invention within the divers face mask.

FIG. 3 is a side elevational view of a diver showing placement of certain components of the invention in his face mask.

FIG. 4 is a schematic representation of the tape drive mechanism of the invention showing the relative location of the component parts thereof.

FIG. 5 is a block diagramatic showing of the circuit arrangement of the speech processor according to the invention.

DESCRlPTION OF THE PREFERRED EMBODIMENT Referring to FIG. I, a surface salvage vessel 11 is shown engaged in a diving operation. Diver 12, working beneath the surface of the water and assisting vessel 11 in recovering a sunken object 113, is shown attaching a lifting net placed about object 13 to the distal end of a line lowered from surface vessel 11. The diver 12 is in communication with surface vessel lit by means of waterborne compressional wave transmitters as indicated by the arcuate wave fronts l6 radiating upward from diver 12. Such communication equipment is well known in the diving arts and frequently referred to by its military designation as WQC or UQC equipment.

Referring to FlGS. 2 and 3 the position of the control components of the system of the invention in the face mask of diver 12 is illustrated. As shown, diver 12 is wearing a face mask l7 which covers the full facial area so as to permit speech while located under water. Diver 12 is also shown as wearing a headset l8 which provides an aural signal to diver 12 of his own speech as well as messages from persons with whom he is communicating. The microphone of the system of the invention is indicated at 19 and is placed adjacent the mouth of diver l2 inside a suitably shaped mouthpiece. Alongside microphone 19, a suitable speed control 21 is placed. This placement of control 21 enables diver 12 to manipulate the control with his tongue such as to effect manual control of the communication system. Headset l8 and microphone l9 and control 21 are joined to the communication equipment by means of

electrical connectors

22 and 23, FIG. 2, which may be joined to a single waterproof conductor.

Because a variety of underwater microphones and headsets may be used in practice of the invention no particular structural details are given in the instant description, however, for purposes of completeness microphone l9 and headset 1% may be considered to be that shown by U.S. Pat. No. 3,562,451 granted on Feb. 9, l97l to Walter W. Mullen, Jr., et al. for Microphone and Head Set for Underwater Swimmer."

Referring to FIG. 4, the drive arrangement and relative positioning of the various recording components used in the system of the invention is illustrated. As shown, the invention employs a tape cassette 24 which serves as a supply and take-up reel for a magnetic recording tape as well as a storage means therefor. The tape wound on cassette 24 is unwound from a supply spool thereof by a drive capstan 25 and a pinch roller 26. Such an arrangement is common in the tape recording arts, however, as will be apparent to those versed in the art, the relative positioning of capstan 25 and 26 to the standard cassette 24 differs from that which is normally employed.

Drive capstan 25 and pinch roller 26 transport the magnetic tape over a recording head arrangement 27 and transfer it to a storage bin 28.

Storage bin 28 is depicted as simply an open-top container such as a box which is positioned to receive a tape as it passes between drive capstan 25 and pinch roller 26. Of course, other, more sophisticated, arrangements for the storage of the recording tape prior to its playback may be used if desired. Such arrangements are well known in the tape recording arts and, accordingly, need not be described in detail for the understanding of this invention.

During periods of playback, the tape is withdrawn from storage bin 28 by means of a drive capstan 3ll and a pinch roller 32 which are positioned to pass the tape across a suitable playback head 33.

As illustrated, a sensor switch 29 is placed within the confines of the tape loop which is drawn out from cassette 24 by means of drive capstan 25 and 31. As the tape is rewound, the tape loop contacts switch 29, moving it to the dotted line position, in order to actuate the closing action of the switch. The electrical function of the closing of the switch will be explained in greater detail as the description of the invention proceeds, however, it should be noted that the interruption of drive action of drive capstan 31 prevents the drive mechanism from rewinding more tape than has been used to record the speech message.

Referring to H6. 5, a block diagrammatic representation of the system of the invention is illustrated. As shown, microphone 119 is connected to an amplifier 34. Amplifier 34 is bridged by an equalization circuit 35 which may be adjusted to provide uniform gain over the desired frequency spectrum. In this regard, it

. should be noted that microphone I9 should have a good frequency response over the desired audio spectra including the higher frequency portion of the voice spectra. That is, microphone 19 should have a higher frequency response characteristic than that normally associated with communication microphones. The output of amplifier 34 is connected to recorder head 27.

Microphone 19 is also connected to a voice operated switch 36. Voice operated switch 36 may be any of several known constructions in the prior art. Such switches have application in a wide variety of electronic fields and a person skilled in the electronics arts will have little difficulty in selecting an appropriate circuit which is compatible with the particular equipment and location used. However, for purposes of completeness it should be noted that the circuit described in the article Transistorized VOX appearing on pages 415 through 417 of the I972 edition of The Radio Amateurs Handbook. published by the American Relay League of Newton, Connecticut, has proven satisfactory in'developmental models of the circuit of the invention.

The outputs from a voice operated switch 36 are con- I nected to a suitable motor control circuit 37. The output of voice operated switch 36 corresponding to presence of voice is connected to the on input for control circuit 37 and the output from voice operated switch 36 corresponding to the absence of voice input is connected to the off input of motor control circuit 37. Motor control circuit 37 controls recorder motor 38 by suitable circuit connection therebetween and, if desired. may comprise a simple relay circuit. However, motor circuit control circuit 37 may include a solid state switching system to control the operation of record motor 38 as is conventional in the motor control arts. Of course, this simplified circuitry is possible because motor 38 is a fixed speed motor as will be understood by those familiar with the magnetic recording art.

The output of voice operated switch 36 corresponding to the absence of voice signal is connected to a second motor control circuit 39 which is used to control the play motor 41. As shown, the connection to voice operated switch 36 serves as the on" signal for motor control circuit 39. The off input for motor control circuit 39 is supplied by switch 29, which as previously described is operated by the take-up of the loop from storage bin 28 (FIG. 4).

The play motor 41 is a different motor than record motor 38 and is unusual in the magnetic recording arts in that it is a variable speed motor changing its speed of rotation in response to a voltage variation of the input. Thus, motor control circuit 39 is of the variable impedance type commonly employed in the control of variable speed electric motors. A wide variety of motor controls are known in the art which are capable of regulating the speed of a voltage control meter. Accordingly, no detailed description of a circuitry comprising motor control 39 is deemed necessary for the understanding of the invention. However, for purposes of completeness. it should be noted that motor speed control 39 may simply be a variable resistance network.

In addition to the switching functions used to control motor circuit 39, a circuit is also responsive to control inputs from an auxiliary or secondary speed control includes tongue operated control 2! previously described in connection with FIGS. 2 and 3.

Secondary speed control is shown as also containing a depth responsive control 42 which varies its impedance in response to the change in ambient pressure and hence the depth at which diver i2 is operating. Depth sensor 42 may simply be another potentiometer similar to 21 whose position is controlled by means of aneroid-bellows arrangement. However, other, more sophisticated pressure responsive means which are known in the art may be employed if desired.

Secondary speed control circuit 40 is also seen to include a gas mixture selection circuit 43 which, like depth sensor 42, may be a variable impedance network such as a plurality of switch resistors or a potentiometer which is manually set in accordance with the particular gas mixture which diver I2 is to breath.

As previously noted, motor 41 is connected to drive capstan 31, FIG. 4, to move the magnetic tape past playback head 33. The electrical signal output playback head 33 is amplified by means of suitable amplification means 44 which, like amplifier 34, is bridged by an equalization network, shown at 45. The equalized output of amplifier 44 is then connected to the existing communications equipment as indicated by the arrow in FIG. 5.

As previously noted, the particular communication equipment employed in the diver communication sys tem is relatively unimportant for the understanding and practice of the invention and the invention may be used with either a fixed wire or the WQC 0r UQC type of communication equipment. While the foregoing description and discussion will engable a person versed in the acoustic engineering arts to fabricate and use the invention, the invention will be better understood thus enabling better selection of means 40. As illustrated, secondary speed control 40 components and design circuitry by reference to the following description of the operation of the system.

MODE OF OPERATION Referring to FIGS. 1 through 3, the operation of the system of the invention commences with diver I2 donning mask 17 and positioning the breathing portion thereof in close cooperation with his mouth and nose regions such that microphone I9 and tongue operated control 21 may be operated.

Conductors

22 and 23 are then connected to the remainder of the system of the invention as illustrated schematically in FIGS. 4 and 5. The device of the invention may be physically located at any convenient position upon the divers person including his breathing back pack or upon the facial mask itself. In developmental models of the invention, the system shown in FIGS. 4 and 5 as physically located withinthe housing for the existing WQC or UQC equipment. The equipment occupies a very small cubic volume measuring only three and seven-eights by two and three-eights by one inch volume and may be operated from a contained battery powered supply.

When communication is desired, diver I2 speaks into microphone 19 which operates voice operated switch 36 to start the drive 25 and controller 26 into the operation to record a spoken message on tape on cassette 24. After an appropriate lapse of time, or at the conclusion of the brief spoken message, diver 12 stops talking and the voice operated switch 36 is toggled such as-to stop drive capstan 25 and start drive capstan 31 by means of energization and motor control 39 and play motor 41. As this drive capstan 31 takes up the film loop of storage bin 28 the loop contained therein dimensishes in size until it contacts the operating control switch 29 moving it to its dotted line position (FIG. 4). This activates switch 29 so as to initiate to off" control for motor control 39 leaving the system inactive'until the next spoken command.

The speed of the playback motor 41, as previously noted, is controlled by means of a depth sensor 42, gas mix select 43, and tongue-operated control 21. Depth sensor 42 and gas mix select 43 may be considered voice controlled for the speed range and tongue operated control 21 a fine adjust control. The operation of tongue-operated control 21 is advantageous in that it gives diver 12 a control for the sound of the transmitted message. Diver l2 hears the audio portion of transmitter message in his headset l8 and therefore is able to operate the speed of playback motor 41 to obtain an optimum amount of intelligibility. At the conclusion of the dive, cassette 24 may be removed and a new cassette inserted thereby perserving a record of the divers portion of the message exchange. This is a highly advantageous feature of the present system in that a documentary record ofa scientific or explatory dive may be retained as the record was obtained since, in many instances, the received message is distorted by external transmission effects such as reverberation, absorption, and acoustic interference.

The foregoing description, taken together with the claims constitute a disclosure such as to enable persons skilled in the electronics and marine engineering arts and having the benefit of the teachings contained therein to make and use the invention. Further, the structure herein described meets the objects of invention and generally constitutes a meritorious advance in the art unobvious to such an aritsan not having the benefits of these teachings.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. and. it is therefore understood that within the scope of the disclosed inventive concept, the invention may be practiced otherwise than specifically described.

What is claimed is:

l. A speech processing system for use by a wearer of a face mask which includes breathing gas supply mouthpiece means comprising:

a microphone attached to said face mask and positioned within said mouthpiece near the mouth of the wearer to produce electrical signals in response to the voice of the wearer;

an amplifier circuit connected to said microphone to receive the electrical signals therefrom and to increase the electrical power thereof;

a voice operated switch circuit connected to said microphone to receive the electrical signals therefrom and to establish separate switching circuits corresponding to the presence and the absence of the voice of the wearer;

tape recorder/playback means carried by the wearer having separate drive mechanisms for the record and playback functions and separate, fixed record and playback heads, said record head being connected to said amplifier circuit for recording the amplified voice signals;

a first motor control circuit means connected between said voice operated switch and said record drive mechanism of said tape recorder/playback means to operate the record drive mechanism at a fixed first speed during the periods when the voice of the wearer is present;

a second motor control circuit means connected between said voice operated switch and said playback drive mechanism for operation of said playback mechanism at a second speed which is slower than said first rate of speed; and

switch means connected to said second motor control circuit means for stopping the operation of playback drive mechanism after a predetermined length of tape has been driven by said playback I drive mechanism.

2. A speech processing system according to claim 1 further including an equalization network circuit means connected across said amplifying circuit for optimizing the response of the microphone over a predetermined frequency range.

3. A speech processing system according to claim 1 in which said tape recorder/playback means includes a cassette tape storage mechanism.

4. A speech processing system according to claim 3 in which the aforesaid tape recorder/playback means includes a tape storage bin to receive tape from the aforesaid record drive mechanism prior to being fed back to said cassette tape storage mechaism.

5. A speech processing system according to claim 1 wherein said second motor control circuit means is also connected to secondary speed control means to alter the playback speed in response thereto.

6. A speech processing system according to claim 5 in which said secondary speed control circuit means includes an impedance circuit which is manually set to provide an output which corresponds to the particular gas mixture being used by the wearer as a breathing gas.

7. A speech processing system according to claim 5 in which said secondary speed control circuit includes an impedance circuit which has an output which is a predetermined function of the ambient pressure at which the wearer is operating.

8. A speech processing system according to claim-5 in which said secondary speed control circuit includes a manually adjustable variable impedance means.

9. A speech processing system according to claim 8 in which said manually adjustable is a variable resistor which is positioned within said mouthpiece and adjacent the aforesaid microphone and is configured to be operated by the tongue of the wearer.

Claims

1. A speech processing system for use by a wearer of a face mask which includes breathing gas supply mouthpiece means comprising: a microphone attached to said face mask and positioned within said mouthpiece near the mouth of the wearer to produce electrical signals in response to the voice of the wearer; an amplifier circuit connected to said microphone to receive the electrical signals therefrom and to increase the electrical power thereof; a voice operated switch circuit connected to said microphone to receive the electrical signals therefrom and to establish separate switching circuits corresponding to the presence and the absence of the voice of the wearer; tape recorder/playback means carried by the wearer having separate drive mechanisms for the record and playback functions and separate, fixed record and playback heads, said record head being connected to said amplifier circuit for recording the amplified voice signals; a first motor control circuit means connected between said voice operated switch and said record drive mechanism of said tape recorder/playback means to operate the record drive mechanism at a fixed first speed during the periods when the voice of the wearer is present; a second motor control circuit means connected between said voice operated switch and said playback drive mechanism for operation of said playback mechanism at a second speed which is slower than said first rate of speed; and switch means connected to said second motor control circuit means for stopping the operation of playback drive mechanism after a predetermined length of tape has been driven by said playback drive mechanism.

8. A speech processing system according to claim 5 in which said secondary speed control circuit includes a manually adjustable variable impedance means.