U.S. patent number 3,789,353 [Application Number 05/320,781] was granted by the patent office on 1974-01-29 for diver communication system.
This patent grant is currently assigned to The United States of America as represented by the Secretary of the Navy. Invention is credited to Earl Kent Hunter, Don G. Smith.
United States Patent |
3,789,353 |
Hunter , et al. |
January 29, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
DIVER COMMUNICATION SYSTEM
Abstract
An underwater diver communication system is disclosed as
including a voice ctuated transmitter for broadcasting speech
signals throughout an ambient subaqueous environmental medium
combined with a two-channel, binaural, speech signal receiver by
means of a common local oscillator connected therebetween which, in
turn, effects relative phase enhancement in the channels thereof.
In addition, the two channels of said binaural receiver incorporate
substantially identical adjustable gain amplifiers, respectively,
the gains of which are identically regulated by a single control
signal from a unique feedback type of signal amplitude enhancement
circuit that is effective to further distinguish the amplitudes of
the speech signals being processed within one receiver channel
relative to those being processed within the other receiver
channel, to thereby facilitate the localization of the speech
signals received by said diver from said ambient subaqueous
environmental medium.
Inventors: |
Hunter; Earl Kent (Gig Harbor,
WA), Smith; Don G. (Shalimar, FL) |
Assignee: |
The United States of America as
represented by the Secretary of the Navy (Washington,
DC)
|
Family
ID: |
23247846 |
Appl.
No.: |
05/320,781 |
Filed: |
January 3, 1973 |
Current U.S.
Class: |
367/132;
128/201.19; 367/124; 381/1; 128/201.27; 367/129; 455/40 |
Current CPC
Class: |
G01S
3/8036 (20130101) |
Current International
Class: |
G01S
3/00 (20060101); G01S 3/803 (20060101); G01s
003/80 () |
Field of
Search: |
;340/3R,5T,6R,16R
;325/16,28 ;179/1UW |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Farley; Richard A.
Attorney, Agent or Firm: Sciascia; Richard S. Doty; Don D.
David; Harvey A.
Claims
What is claimed is:
1. A communications system, comprising in combination:
a heterodyne transmitter for broadcasting a first signal within a
first predetermined frequency range throughout a predetermined
environmental medium;
means connected to said transmitter for effecting the actuation
thereof in response to a second signal within a second
predetermined frequency range;
a heterodyne receiver, having a pair of receiving channels, each of
which includes a voltage controlled amplifier, contiguously
disposed with said heterodyne receiver, for receiving signals
within said first predetermined frequency range and heterodyning
them back within said second frequency range; and
means connected between the outputs and control inputs of the
voltage controlled amplifiers of said pairs of receiving channels
for regulating the respective amplifications thereof in proportion
to the peak of the sum of the output signals from said voltage
controlled amplifiers.
2. The device of claim 1, wherein said communication system is a
binaural underwater communication system, and wherein said
predetermined environmental medium is water.
3. The device of claim 1, wherein said communication system is a
binaural underwater communication system, wherein said
predetermined environmental medium is water, and wherein said
second signal within a second predetermined frequency is a signal
that is generated by and proportional to the sonic energy produced
by the human voice.
4. The device of claim 1, wherein said heterodyne transmitter
comprises:
a microphone;
a low pass filter connected to the output of said microphone;
a balanced modulator having a pair of inputs and an output, with
one of the inputs thereof effectively connected to the output of
said low pass filter;
a normally closed gate having a data signal input, a control signal
input, and an output, with the data signal input thereof connected
to the output of said balanced modulator, and with the control
signal input thereof adapted for effecting the opening thereof in
response to a control signal within a predetermined frequency
range;
a band pass filter connected to the output of said normally closed
gate; and
a transmitting transducer effectively connected to the output of
said band pass filter.
5. The device of claim 1, wherein said heterodyne transmitter
comprises:
a microphone;
a low pass filter connected to the output of said microphone;
a balanced modulator having a pair of inputs and an output, with
one of the inputs thereof effectively connected to the output of
said low pass filter;
a normally closed gate having a data signal input, a control signal
input, and an output, with the data signal input thereof connected
to the output of said balanced modulator, and with the control
signal input thereof adapted for effecting the opening thereof in
response to a control signal within a predetermined frequency
range;
a band pass filter connected to the output of said normally closed
gate;
a transmitting transducer effectively connected to the output of
said band pass filter; and
a local oscillator connected to the other input of said balanced
modulator.
6. The device of claim 1, wherein said heterodyne transmitter
comprises:
a microphone;
a low pass filter connected to the output of said microphone;
a balanced modulator having a pair of inputs and an output, with
one of the inputs thereof effectively connected to the output of
said low pass filter;
a normally closed gate having a data signal input, a control signal
input, and an output, with the data signal input thereof connected
to the output of said balanced modulator, and with the control
signal input thereof adapted for effecting the opening thereof in
response to a control signal within a predetermined frequency
range;
a band pass filter connected to the output of said normally closed
gate;
a transmitting transducer effectively connected to the output of
said band pass filter;
a local oscillator connected to the other input of said balanced
modulator; and
means effectively connected between the output of said low pass
filter and the voltage control input of the aforesaid normally
closed gate for effecting the opening thereof in response to the
signal received from the output of said low pass filter.
7. The device of claim 1, wherein said heterodyne transmitter
comprises:
a microphone;
a low pass filter connected to the output of said microphone;
a balanced modulator having a pair of inputs and an output, with
one of the inputs thereof effectively connected to the output of
said low pass filter;
a normally closed gate having a data signal input, a control signal
input, and an output, with the data signal input thereof connected
to the output of said balanced modulator, and with the control
signal input thereof adapted for effecting the opening thereof in
response to a control signal within a predetermined frequency
range;
a band pass filter connected to the output of said normally closed
gate;
a transmitting transducer effectively connected to the output of
said band pass filter; and
means effectively connected between the output of said low pass
filter and the voltage control input of the aforesaid normally
closed gate for effecting the opening thereof in response to the
signal received from the output of said low pass filter.
8. The device of claim 1, wherein said means connected between the
outputs and control inputs of the voltage control amplifiers of
said pairs of receiving channels for regulating the respective
amplifications thereof in proportion to the peak of the sum of the
output signals from said voltage controlled amplifiers
comprises:
a summing amplifier having a pair of inputs and an output, with the
inputs thereof respectively connected to the outputs of said
voltage controlled amplifiers; and
a direct current peak detector connected between the output of said
summing amplifier and the control inputs of said voltage control
amplifiers.
9. The invention of claim 1, further characterized by a face mask
means surrounding said communication system for the housing thereof
therein when said face mask means is worn by a swimmer-diver.
10. The invention of claim 1, further characterized by a face mask
means surrounding the transmitter and transmitter actuation means
of said communication system for the housing thereof therein when
said face mask means is worn by a swimmer-diver.
11. The invention of claim 1, further characterized by a local
oscillator connected to said heterodyne transmitter and each of
said pair of receiving channels of said heterodyne receiver for
supplying a predetermined heterodying signal thereto.
12. The device of claim 1, wherein each of said pair of receiving
channels of the aforesaid heterodyne receiver comprises:
a receiving hydrophone;
a band pass filter effectively connected to the output of said
receiving hydrophone;
a voltage controlled amplifier having a data signal input, a
control input, and an output, with the data signal input thereof
connected to the output of said band pass filter, and with the
control input responsive to a voltage control signal;
a balanced demodulator having a pair of inputs and an output, with
one of the inputs thereof connected to the output of said voltage
controlled amplifier;
a low pass filter connected to the output of said balanced
demodulator; and
an earphone effectively connected to the output of the aforesaid
low pass filter.
13. The device of claim 12, wherein the hydrophones of said pair of
receiving channels are physically disposed in such diametrically
opposed manner as to be responsive to acoustical energy arriving
thereat from predominantly opposite directions.
14. The device of claim 12, wherein the hydrophones of said pair of
receiving channels are physically disposed in such manner as to be
responsive to acoustical energy arriving thereat from within
similar oppositely directed cardioid response patterns.
15. An underwater communication system, comprising in
combination:
a microphone;
a first low pass filter connected to the output of said
microphone;
a first preamplifier connected to the output of said low pass
filter;
a balanced modulator having a pair of inputs and an output, with
one of the inputs thereof connected to the output of said first
preamplifier;
a gate having a data signal input, a control input, and an output,
with the data signal input thereof connected to the output of said
balanced modulator;
a voice operated switch connected between the output of the
aforesaid first preamplifier and the control input of said
gate;
a first band pass filter connected to the output of said gate
a first power amplifier connected to the output of said first band
pass filter;
a transmitting transducer connected to the output of said first
power amplifier;
a first hydrophone;
a second preamplifier connected to the output of said
hydrophone;
a second band pass filter connected to the output of said second
preamplifier;
a first voltage controlled amplifier having a data signal input, a
control input, and an output, with the data signal input thereof
connected to the output of said second band pass filter;
a first balanced demodulator having a pair of inputs and an output,
with one of the inputs thereof connected to the output of said
first voltage controlled amplifier;
a second low pass filter connected to the output of said first
balanced demodulator;
a second power amplifier connected to the output of said second low
pass filter;
a first earphone connected to the output of said second power
amplifier;
a second hydrophone;
a third preamplifier connected to the output of said second
hydrophone;
a third band pass filter connected to the output of said third
preamplifier;
a second voltage controlled amplifier having a data signal input, a
control input, and an output, with the data signal input thereof
connected to the output of said third band pass filter;
a second balanced demodulator having a pair of inputs and an
output, with one of the inputs thereof connected to the output of
said second voltage controlled amplifier;
a third low pass filter connected to the output of said second
balanced demodulator;
a third power amplifier connected to the output of said third low
pass filter;
a second earphone connected to the output of said third power
amplifier;
an oscillator connected to the other inputs of said first and
second balanced demodulators and the aforesaid balanced
modulator;
a summing amplifier having a pair of inputs and an output, with the
inputs thereof respectively connected to the outputs of said first
and second voltage controlled amplifiers; and
a direct current voltage peak detector having an input and an
output, with the input thereof connected to the output of said
summing amplifier, and with the output thereof connected to the
control inputs of the aforesaid first and second voltage controlled
amplifiers.
16. The invention of claim 15, further characterized by means for
housing said underwater communication system in a waterproof manner
and in contiguous disposition with the mouth and ears of an
underwater swimmer-diver.
Description
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
The present invention relates, in general, to communication
systems, and, in particular, it is a sonar system for communicating
and navigating within a subaqueous medium. In even greater
particularity, the invention is a binaural sonar system combined
with a face mask in such unique manner that it facilitates the
communication, target search, navigation, and homing operations of
swimmers and divers operating within waters which would otherwise
constitute adverse environmental conditions.
DESCRIPTION OF THE PRIOR ART
Heretofore, numerous sonar and underwater communication systems
have been employed by swimmers, divers, and various and sundry
manned and unmanned underwater vehicles. For some purposes, they
have proven to be quite satisfactory; however, for swimmer-diver
communication, homing, and navigation purposes, they usually leave
a great deal to be desired.
SUMMARY OF THE INVENTION
The instant invention overcomes many of the disadvantages of the
prior art, in that it enables underwater swimmers to communicate
intelligibly in a manner that is somewhat similar, as far as
psychological and physiological experiences are concerned, to
normal talking and hearing in an atmospheric environment by a human
being.
It is, therefore, an object of this invention to provide an
improved underwater sonic communication system.
Another object of this invention is to provide an improved
echo-search-ranging system.
Still another object of this invention is to provide an improved
sonar system in which the output thereof is produced as enhanced
binaural signals which provide bearing information of received
acoustical energy when listened to by human ears.
A further object of this invention is to provide an acoustical
communication system having an improved signal-to-noise ratio.
Another object of this invention is to provide an improved
underwater communication and face mask combination which will
essentially free a swimmer-diver from the burden of large, heavy,
cumbersome, communication apparatus, thereby allowing said
swimmer-diver considerably greater freedom of movement and complete
freedom of hand use within sea water or the like.
A further object of this invention is to provide an improved method
and means for localizing the source of various and sundry
underwater sounds.
Still another object of this invention is to provide a method and
means for improving the binaural capabilities as a result of
incorporating both amplitude and phase discrimination techniques in
an underwater communication system.
Another object of this invention is to provide restoration of
binaural hearing and acoustical signal localization abilities to an
individual operating in an otherwise acoustical signal diffusing
environmental medium, such as pressurized helium, sea water, or the
like.
Another object of this invention is to provide an improved voice
activated underwater communication system.
Another object of this invention is to provide an underwater
communication system that is easily and economically manufactured,
operated, and maintained.
Other objects and many of the attendant advantages will be readily
appreciated as the subject invention becomes better understood by
reference to the following detailed description, when considered in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a schematic elevational view of the transmitter portion
of the subject invention mounted in and in cooperative association
with a swimmer-diver face mask;
FIG. 2 is a schematic perspective view of headset and earphone
arrangements employed which constitutes the receiver portion in the
subject invention;
FIG. 3 is a block diagram of the swimmer-diver underwater
communication system of this invention; and
FIG. 4 is a graphical representation of the acoustical response
patterns of the receiving hydrophones of the instant invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1, there is shown a face mask 11 of the type
which is typically worn by swimmers and divers. Obviously, many
different face masks, diver's helmets, etc., are commercially
available, and anyone thereof may be employed as a component of
this invention, as long as it allows freedom of lip and jaw
movements, has sufficient room in it to allow emplacement of the
transmitting and/or receiving apparatus therein, and meets the
physiological requirements of the swimmer-diver.
Preferably, the acoustic frequency response of the speaking cavity
of face mask 11 should be determined under all environmental
conditions, so that it may be frequency compensated -- both
electronically and mechanically -- so that the overall system will
have as flat a frequency response as possible and, thus, enhance
communication intelligibility. As a general rule, however, it has
been found that most conventional face masks have a 6 db per octave
signal attenuation or downslope, with a resonant peak somewhere
between 500 and 1,000 Hz. Therefore, it is necessary to compensate
for such downslope, if optimum operation is to be obtained. Such
compensation is accomplished within the transmitter electronics
portion 12 of the invention, as will be discussed more fully
subsequently.
So as to make the subject system self-contained, a rechargeable
battery pack 13 is deployed within mask 11 and is connected to
encased electronics portion 12 by means of intercabling 14.
Intercabling 14, in addition to supplying power to the electronic
circuitry, also transmits electrical signals from a transmitter 15
-- a part of said electronics circuitry 14 -- to a broadcasting
electroacoustical transducer 16 located on the other side of the
face mask, in this particular instance. Disposed in cable 14 is a
connector 17, which enables transmitter 15 to automatically be
turned off merely by breaking the electrical circuit thereat. It is
preferably an Electro Oceanics 59F2F-1 connector that can be
connected and disconnected underwater.
All of the foregoing elements 12 through 17 are housed in such
manner in any suitable containers as would be necessary to provide
water and pressure proofness. Details of such housing or containers
are not disclosed specifically herewith because it would be well
within the purview of one skilled in the art having the benefit of
the teachings presented herein to make and use whatever ones
thereof would be required for any given operational circumstances.
Of course, they may be epoxy coated to insure waterproofness, if
desired.
A microphone 18 is also included within face mask 11. It, too, must
be both pressure and waterproof. In this particular instance, it
has been found, for example, that a three-quarter inch diameter
ceramic bimorph connected in series, potted in any suitable potting
compound, such as, for example, a self-leveling silicone rubber
compound, and encased in a neoprene cup is quite satisfactory as
microphone 18, inasmuch as such element has approximately a 6 db
per octave upslope and will, thus, help compensate for the
aforementioned downslope of mask 11. Also, it is relatively
distortion free from 300 Hz to 6,000 Hz, thereby having a bandwidth
that is the minimum allowable to capture optimum speech
intelligibility, especially when the speech spectrum is upshifted
in frequency, due to a high pressure water or helium gas ambient
environment. Of course, any other suitable microphone may be
employed as microphone 18, if so desired by the artisan or the
swimmer-diver.
An external connector 19 provides a preamplified speech output for
use by voice recorders, wire communication systems, and other
external and/or remote systems, requiring voice input (not shown
and not a part of this invention).
FIG. 2 shows a headset 20 which preferably includes the receiver
circuitry 21 of the subject system, the electronics of which will
be discussed more fully below. Disclosed is a pair of receiver
channels which are signal processors for the ears of the
swimmer-diver, respectively. Hence, headset 20 contains a right ear
receiver channel 22 and a left ear receiver channel 23, each of
which includes substantially similar receiver channel components
that are interconnected by a unique binaural amplitude enhancement
circuit that may be physically disposed in the housing of either
one thereof (or optionally within the electronics portion of the
aforesaid face mask 11, if so desired). Said receiver channels will
be discussed in greater detail in conjunction with FIG. 3.
Receiver channels 22 and 23 are, in this particular embodiment,
respectively encased in any suitable pressure proof, waterproof
housings 24 and 25. They include receiving hydrophones 26 and 27,
respectively, which are mounted on the outer sides thereof for
diametrically opposed response to incoming acoustical energy which,
thus, effectively impacts thereon from opposite directions, just as
the ears do for any given human being. As will be explained in
better detail subsequently, such opposite directional response
characteristics play an important part in enabling the
swimmer-diver to localize and determine the direction from which a
sound is coming within water, sea water, or the like -- something
which, in actual practice is exceedingly difficult to do.
The inside surfaces of receiver channels 22 and 23 constitute
earphones 28 and 29, respectively, and, of course, they are adapted
for fitting firmly against the ears of the swimmer-diver.
A headpiece 31 interconnects both receiver channels both
electrically and physically and enables the receiver to be properly
-- and conventionally -- mounted on the swimmer's head. As will be
discussed more fully in conjunction with FIG. 3, a unique binaural
enhancement circuit (not shown in FIG. 2) is appropriately
connected between the receiver channels; consequently, it may be
physically located anywhere in headset 20 that would be
structurally and electrically convenient.
A pair of external connectors 32 and 33 are optionally mounted on
the receiver channels, in order to connect external and perhaps
remote recording equipment thereto.
Referring now to FIG. 3, wherein the elements disclosed are
indicated by the same reference numerals as employed in the
disclosure thereon in FIGS. 1 and 2, insofar as it is possible and
practical. Disclosed is the aforesaid single sideband transmitter
15 which, of course, may be incorporated as a portion of
electronics 12 in swimmer-diver face mask 11. Included therein and
also preferably mounted in face mask 11 is the aforementioned
microphone 18, the output of which is connected to the input of a
6,000 Hz low pass filter 42, employed for the purpose of
eliminating external noise above the desired human speech band of,
say, from 300 to 6,000 Hz and to provide approximately a 6 db per
octave signal upslope or enhancement, to fully compensate for the 6
db per octave signal attenuation or downslope inherently caused by
the face mask.
The output of low pass filter 42 is connected to the input of an
adjustable gain preamplifier 43, which is preferably designed in
such manner that a flat frequency response occurs within the
transmitter portion of the invention. The output of preamplifier 43
is connected to one of the inputs of a balanced modulator 44 and
the input of an input signal actuated switch which, in this
particular case, effectively operates as a selective activator
filter and voice operated switch (VOX) 45.
As would be obvious to one skilled in the art, voice operated
switch 45, as it is presently connected to its associated
components, is, in fact, actuated by the electrical signal
equivalent of the human voice after it has been properly filtered
and amplified. Such arrangement has been employed for two reasons:
(1) spurious ambient signals will not pass through low pass filter
42, which prevents inadvertent transmission by the transmitter from
being effected by signals other than the diver's voice; and (2) the
transmitter will not be actuated by changes in ambient pressure, in
the event the diver changes water depths. Of course, the voice
operated switch should be conventionally designed to be inoperative
below a given threshold or voice volume and selective to only diver
voice signatures, thereby preventing the broadcasting of such
undesirable and noise producing signals as diver breathing and
movement signals and water bubble sounds. Any commercially
available or conventional voice operated switch means having the
above mentioned operational characteristics may be employed as
voice operated switch 45 in the subject invention.
The other input of balanced modulator 44 is connected to the output
of an 8.087 KHz local oscillator 46, which may or may not be
considered as being part of transmitter 15. Since local oscillator
46 is used as the heterodyning signal generator for both the
transmitter and the receiver in this preferred embodiment, it is
considered as being separate from each thereof. However, it should
be understood that both the transmitter and the receiver may have
their own individual local oscillator, if so desired, as long as
the signal frequencies thereof are identical.
On the other hand, local oscillator 46 alone is incorporated in
this disclosed preferred embodiment of the invention because it has
been determined that so doing enhances the phase aspect of the
binaural characteristics produced thereby as a result of using a
common carrier frequency in both demodulators which cause the
demodulated output signals therefrom to retain any phase
differences between the receiver channels.
The output of balanced modulator 44 is connected to the data signal
input of a gate 47, the control input of which is connected to the
output of voice operated switch 45. In this particular instance,
gate 47 is a voltage controlled gate which is normally closed but
is opened whenever a predetermined voltage signal is supplied to
the control input thereof as a result of switch 45 being
effectively opened by the speech of the swimmer-diver. Of course,
switch 45 is actually opened by the filtered and amplified
electrical signal that is proportional to the acoustical speech
signal supplied to microphone 18 minus any spurious signals, such
as, for instance, breathing sounds, and the like. But when it is
opened thereby, the actuating signal also effectively passes
through switch 45 and then becomes the gate control signal which,
in turn, effects the opening thereof, so that the output signal
from balanced modulator 44 can pass therethrough. Obviously, such
switch and gate operations occur simultaneously and
instantaneously, for all practical purposes.
The output of gate 47 is connected to the input of a bandpass
filter 48, in order to eliminate the lower sideband output signals
effectively supplied thereto from modulator 44, and the output of
filter 48, in turn, connected with a power amplifier 49 to the
input of electroacoustical transducer 16 adapted for broadcasting
the aforesaid modified speech signals throughout the subaqueous
medium, such as water, sea water, or the like, within which the
swimmer-diver is submerged or throughout any other predetermined
suitable environmental medium. Of course, said modified speech
signals are, in fact, the communication signals which allows one
diver to talk to another diver having similar transmitting and
receiving apparatus while both are under water.
A receiver system 21 is used to receive the talk signals of
substantially comparable frequencies and qualities from other
divers, as suggested above. It contains the aforementioned pair of
signal processing channels 22 and 23 which are adopted for
supplying said speech signals to the ears of a diver, respectively.
However, as will be explained in greater detail subsequently, they
do it in such manner as to uniquely improve the binaural
characteristics thereof and, thus, enable a diver to localize and
determine the direction from which talk signals are coming, even
though the entire communications system constituting this invention
may have been miniaturized or compacted by the employment of solid
state or other suitable manufacturing techniques to the extent that
it is combined with the diver's face mask and be in proximity with
his head and ears.
Receiver channel 22 includes the aforesaid electroacoustical
hydrophone 26, the output of which is connected through a
preamplifier 56 to the input of bandpass filter 57 of the type that
is similar to the aforesaid bandpass filter 48 in transmitter 15.
The output of filter 57 is connected to the data signal input of an
adjustable gain amplifier 58, the gain of which is adjusted in
proportion with whatever voltage signal is supplied to the gain
control input thereof.
The output of amplifier 58 is connected to one of the inputs of a
demodulator 59, with the other input thereof being connected to the
output of the aforementioned local oscillator 46. Again, as
previously suggested, if so desired, receiver 21 may be
self-contained and have its own local oscillator, as long as the
signal frequency thereof is identical to that supplied to balanced
modulator 44 in transmitter 15. Of course, as will be explained
more fully below, demodulator 59 heterodynes the incoming modified
speech signal down to its original frequency range of between 300
and 6,000 Hz, so that it will be intelligible when received by the
diver's ear. For effecting such processing, a low pass filter 61 is
connected to the output of demodulator 59, in order that said diver
only receives the lower side band output -- that is, said 300 to
6,000 Hz talk signals -- therefrom. The output of low pass filter
61 is connected through a power amplifier 62 to the input of the
aforesaid earphone 28, which, as previously indicated, is
physically disposed in contiguous relationship with one of the
divers ears, so that the diver may hear the talk signals emanating
therefrom while he is working in an underwater environment.
In every respect, receiver channel 23 should be as identical as
possible to receiver channel 22; therefore, the components thereof
are substantially identical to the above described components of
said channel 22, respectively. As a result of such arrangement, the
aforesaid hydrophone 27, a preamplifier 65, a bandpass filter 66, a
variable gain amplifier 67, a balanced demodulator 68, a low pass
filter 59, a power amplifier 71, and the aforesaid earphone 29 are
connected in series in the same manner as the components comparable
thereto were series connected in channel 22.
The aforementioned binaural characteristics are considerably
improved in the subject invention by a simple but unique binaural
enhancement circuit 73 which is connected to receiver channels 22
and 23. Said binaural enhancement circuit 73 includes a summing
amplifier 74 having a pair of inputs which are connected to the
outputs of the aforesaid variable gain amplifiers 58 and 67 of
receiver channels 22 and 23, respectively. The output of summing
amplifier 74 is connected to the input of a direct current (DC)
voltage peak detector 75, the output of which is connected to the
gain control inputs of said variable gain amplifiers 58 and 67.
FIG. 4 depicts schematically the top of the head of a diver 81
(otherwise not shown), with right and left hydrophones 26 and 27
physically located in association therewith in such manner that the
respective response patterns are oppositely directed cardioid
patterns 82 and 83, mathematically defined by the expressions 1 +
cos .theta. and 1 - cos .theta., respectively. Also, in this
particular embodiment, said hydrophones are preferably designed so
that the outer cardioid radius (2A), as measured from the center of
diver head 81, is twice the distance (A) of their radius of
intersection, likewise measured from the center of diver head 81.
As will be explained more fully below, such structural arrangement
and dispositions of receiving hydrophones further enhance the
discernment of the diver, as far as the direction of incoming sound
is concerned. Thus, in conjunction with signal enhancement circuit
73 discussed above, the listening characteristics of a
swimmer-diver working underwater are more nearly the same as they
would be if he were working in the atmosphere with only his ears as
the sound receptors.
At this time, it would perhaps be noteworthy that the subject
invention is primarily intended to facilitate the operation of a
diver within water and within considerable depths thereof; however,
it should be understood that it may also be used to an advantage in
other environmental mediums -- such as, for instance, pressurized
helium -- if so desired and designed therefor by one skilled in the
art having the benefit of the teachings presented herewith.
It should also be understood that all of the various and sundry
components of this invention are well known and conventional per
se, and some thereof may have been patented in their own right at
some time in the past. Therefore, it is their interconnection and
interactions that effect the new combinations of elements
constituting this invention and cause the stated improved results
and objectives to be achieved thereby.
MODE OF OPERATION
The operation of the invention will now be discussed briefly in
conjunction with all of the figures of the drawing.
A swimmer-diver wears the face mask and headset disclosed in FIGS.
1 and 2. Hence, he can speak into the transmitter and hear from the
receiver portions thereof without carrying additional apparatus or
without requiring the use of his hands. This, of course, is very
advantageous, because the diver is not handicapped by the unwieldy
burden of an undue load and, furthermore, has his hands free to do
whatever work he desires to do. Moreover, even though he is working
in an underwater environment that is, at least, unnatural and
perhaps hostile to him, he is considerably less disoriented and
can, thus, navigate more easily therein than he otherwise could
without the benefit of the subject invention. In addition, this
arrangement allows complete and natural feedback of the diver's
voice to occur and, hence, facilitates improved speech formation
which, in turn, further enhances intelligibility.
Perhaps, at the outset, the significance of the unique transmitter
and receiver systems 15 and 21 depicted in FIG. 3 should again be
mentioned. As may readily be seen from inspection thereof, as a
result of both thereof using the same local oscillator 46 -- and,
hence, being heterodyned with the same frequency signal having the
same polarity at any given instant -- transmitter 15 and receiver
21 are effectively interconnected and are, hence, perfectly
synchronized, and may thus be considered to be a unique
transmit-receive system in the disclosed preferred embodiment.
However, if they are identical, two independent local oscillators
may be employed, if so desired. In such case, both transmitter 15
and receiver 21 could be considered as being self-contained
units.
As seen from FIG. 1, microphone 18 is located in proximity with the
diver's mouth, so that he may speak into it without undue effort.
Microphone 18 conventionally converts the acoustical energy of the
diver's voice into a proportional electrical speech signal that is
processed by 6,000 Hz low pass filter 42 to remove all external
noise above the speech band, as well as other spurious and feedback
signals. Then, the output is amplified by preamplifier 43 to
provide a 6 db per octave upslope for face mask downslope
compensation purposes, thereby effecting a substantially flat
frequency response which enhances signal intelligibility. The
filtered and preamplified speech signal falls within approximately
the 300 to 6,000 Hz frequency band and is then heterodyned with an
8.087 KHz signal from oscillator 46. At the same time, a
predetermined frequency signature portion thereof passes through
selective filter and VOX 45 and opens gate 47 to let the
heterodyned output signal from balanced modulator 44 pass
therethrough. The output from modulator 44 consists of the upper
and lower side bands having frequencies of 8-14 KHz and 2-8 KHz,
respectively. In order to provide improved intelligibility, a 6,000
Hz speech bandwidth is maintained throughout the subject system;
therefore, only the 8-14 KHz upper side band is passed through band
pass filter 48, after which it is amplified by power amplifier 49
and braodcast or projected into the ambient water by transmitting
transducer 16.
Obviously, speech transmission is primarily intended for receipt by
another diver, but because receiver 21 remains "on" constantly --
so as to require no external cabling or controls -- the speaking
diver receives his own speech signals, which he can hear as a
result of the processing thereof by his own receiver, namely, in
this particular instance, receiver 21. Of course, it should also be
obvious that all of the communicating divers must wear one of the
subject communication systems, if actual communication of the
speaking-hearing type is to occur.
Receiver 21, as illustrated in FIG. 3, receives the incoming speech
signals by means of hydrophones 26 and 27 of receiver channels 22
and 23, respectively. Because both of said receiver channels
internally process the received signals in the same manner, only
channel 22 will be described, in order to keep this disclosure as
simple as possible.
When the 8-14 KHz acoustical speech signals are received from
within the ambient water environment, they are transduced into
electrical signals proportional thereto by hydrophone 26 (say, the
right hydrophone, in this case), after which they are amplified to
a more useful level by preamplifier 56. After such amplification,
they are filtered by 8-14 KHz bandpass filter 57, in order to
delete spurious signals outside the 8-14 KHz band that may exist
therein, thereby improving the signal-to-noise ratio thereof. The
filtered output speech signals from filter 57 are then amplified an
appropriate amount -- as determined by signal enhancement circuit
73, to be explained shortly -- by variable gain amplifier 58 before
being heterodyned down to the original speech frequency range of
from 300 to 6,000 Hz by balanced demodulator 59 and oscillator 46.
Then said original speech frequency output signals from demodulator
59 are filtered by 6,000 Hz low pass filter to insure passage of
audible speech signals only before being amplified to a more useful
level by power amplifier 62 and supplied to the diver's ear -- say,
the right ear, in this particular instance -- by earphone 28. The
aforesaid power amplifier 62 is preferably designed to compensate
for any signal attenuation caused by the downslope of frequency
response inherently introduced by the aforementioned earphone 28
and the human ear being immersed in water.
Due to certain acoustic considerations, a human ear immersed in
water loses some of its ability to localize the source of
underwater sounds. This invention restores such ability to the
swimmer-diver by means of signal amplitude enhancement and
discrimination techniques which, in effect, improve the binaural
aspects thereof. In this invention such binaural effects are
improved by two separate and distinct structural entities, which,
although operative individually, combine associatively to produce
results that are superior to either one used alone or both thereof
merely added together.
One such entity is signal enhancement circuit 73 in combination
with adjustable gain amplifiers 58 and 67 of receiver channels 22
and 23. As mentioned previously, channels 22 and 23 are
substantially identical in structure and operation; therefore, the
analysis of channel 23 will not be belabored herein. However, it
would appear to be noteworthy at this time (for purpose of
emphasis) that the amplification characteristic curves of
amplifiers 58 and 67 should be as identical as possible, if optimum
performance is to be obtained from the overall invention. The
outputs of adjustable gain amplifiers 58 and 67 are supplied to the
inputs of summing amplifier 74 which, in turn, produces a composite
output signal that is proportional to the addition of the voltages
thereof. This composite signal is then peak detected, so as to
produce a direct current (DC) control voltage signal that is
proportional to peak thereof, and such peak DC control signal is
supplied to the control inputs of amplifiers 58 and 67 for
appropriate regulation of the gain thereof. In this particular
case, amplifiers 58 and 67 should be designed by the artisan to be
decreased in gain for an increase in the composite gain control
signal and vice versa.
From the foregoing, it may readily be inferred that if the incoming
speech signal originates at a point directly in front of the diver,
it will be amplified the same amount in amplifiers 58 and 67 and
the diver's ears will hear signals of equal intensity and of the
same phase. On the other hand, in the event the source of the
incoming speech signals is to the right or left of the diver, the
speech signals received by the divers right or left ear will be
stronger and a phase difference will exist proportional to the
degree of offset from center of the source and its frequencies,
depending upon which direction they come. For example, if the sonic
signal source -- say, another diver 85 that is speaking -- is to
the right of the receiving or hearing diver, hydrophone 26 (as best
seen in FIG. 4) will receive a higher power signal than hydrophone
27 because it is closer thereto and because said hydrophones are
directionally oriented for acoustical response in diametrically
opposed directions. In such instance, if, for example, after
cardioid response pattern compensation a 6 volt signal 84 were
sensed by hydrophone 26 and the same signal had attenuated to a 5
volt signal by the time it was sensed by hydrophone 27, then, when
both signals were amplified an equal amount -- say, for example, by
11 -- the right ear would hear a signal proportional to a 66 volt
signal and the left ear would receive a signal proportional to a 55
volt signal, with the voltage difference therebetween being 11
volts instead of 1 volt. Such increase in intensity in the right
ear of the diver would immediately alert him that the speech
signals that he was receiving were coming from his right.
Accordingly, binaural enhancement is achieved in water, in
proportion to the addition of the received signals which
facilitates ascertaining the signal source direction or bearing.
This, in turn, makes it easier for a diver to retain his
orientation, even though he and the person or persons with whom he
is communicating may be working in the dark in deep or turbid
water.
As previously suggested, whenever incoming speech or other signals
arrive from the left or the right of the listening diver, the phase
thereof is delayed at the hydrophone that receives it last, as a
result of their greater travel distance in an aqueous medium. In
addition, the effective intensity differences of the received
signals are enhanced by the respective hydrophone cardioid response
patterns which, in turn, are arranged in diametrically opposed
dispositions as a result of the opposite orientations of the
hydrophones themselves on the head of the diver, as previously
mentioned. Such arrangement and evidence of response patterns can
best be seen in FIG. 4, wherein response pattern 82 of hydrophone
26 is depicted graphically and is mathematically defined by the
expression 1 + cos .theta., where .theta. is the angle measured
around the center (C) of diver head 81, and wherein response
pattern 83 of hydrophone 27 is depicted graphically and is
mathematically defined by the expression 1 - cos .theta., where
.theta. is again the angle measured around the center (C) of diver
head 81. Thus, it may be seen that if speech signals 84 are being
received from a speech source 85 to the right of the front of diver
81, hydrophone 26 would produce an output signal that is
proportional in intensity to RC, while hydrophone 27 would produce
an output signal that is proportional in intensity to LC, and
because RC is greater than LC, the output signal voltage from right
hydrophone 26 would be greater than the output signal voltage from
left hydrophone 27. Such voltage differences, of course, enhance
the binaural aspect of the invention, thereby effectively
simulating the normal hearing characteristics of a human being.
In view of the foregoing, ostensively it should be evident that the
instant swimmer-diver communications system constitutes an
advancement in the art and that, to some extent, it achieves
objectives heretofore unattainable. Accordingly, it is a new and
exceedingly useful method and means for enabling intelligible
communication to occur between people and/or other beings response
to human speech or other transmitted sound.
Concomitantly with the above, as previously suggested, it would
perhaps be noteworthy that it is possible to use the invention as
an active or passive sonar system, wherein the transmitter
broadcasts certain speech or other signals as target search signals
that are received as target echo signals by the receiver, which, in
turn, are then interpreted by the diver as to whether or not a
target has been acquired and, if so, the relative bearing thereof,
or he may merely listen to or home on an incoming sonic signal.
Obviously, other embodiments and modifications of the subject
invention will readily come to the mind of one skilled in the art
having the benefit of the teachings presented in the foregoing
description and the drawings. It is, therefore, to be understood
that this invention is not to be limited thereto and that said
modifications and embodiments are intended to be included within
the scope of the appended claims.
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