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Патент USA US2405226

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Aw@ ë, 1946,
2,405,2ZÉ
W. P. MASON
Low FREQUENCY PROJECTOR 0R HYDROPHONE
Filed Dec. 2s, 1942
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Aug, 6, i946.
w; P. MASON
2,405,226
LOW FREQUENCY PROJECTOR OR HYDROPHONE
Fi led Dec. >28, 1942
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Patented Aug'. 6, 1946
I
2,405,226
UNITED STATES PATENT> OFFICE
2,405,226
LOW FREQUENCY PROJECTOR OR
HYDROPHONE
Warren P. Mason, West Orange, N. J., assignor to
Bell Telephone Laboratories, Incorporated, New
York, N. Y., a corporation of New York
Application December 28, 1942, Serial No. 470,398
5 Claims. (Cl. 177-386)
1
2
This invention relates to multiunit radiating
andV receiving devices and to high power com
pressional wave radiating devices. In the here
inafter described preferred embodiments, illus
trative of the principles thereof, it relates par
ticularly to radiating and receiving devices em
ploying a large number of piezoelectric crystals
and the suppression of secondary lobes, the sep
arate crystals .being constructed and arranged to
respond to frequencies within the audible range.
The drawings consist of two sheets having
fourteen figures, as follows:
which are capable of radiating high power com
pressional energy waves and to compressional
wave energy radiators and receivers which have
on the hull of a ship;
Fig. 2 is a cross-sectional view taken on line
Fig. 1 is a fragmentary view of a plurality
of radiators showing how they may be mounted
2, 2 of Fig. 1 of a crystal showing how the
crystal may be mounted and illustrating the
relationship of the oil and air chambers with
“prismatic” properties.
By way of definition, in the present specifica
tion a prismatic device, for other than light
energy waves, should be understood to be a device
which in transmitting a wave comprising en
ergy of numerous frequencies within a particular
respect thereto;
Fig. 3 is a similar View showing another form
15 of crystal arranged to be insensitive to longi
tudinal waves in the metal frame;
frequency spectrum will spread the frequency
spectrum by imparting a direction, differing for
each frequency, to the several frequencies of the
spectrum or which in receiving energy will re
.
Fig. 4 is a fragmentary circuit »diagram show
ing an electrical circuit equivalent to the bi
morph crystal;
is a similar but more detailed circuit;
is a circuit diagram showing the rela
of the equivalent constants for a crys
particular size as derived in the body
of the specification;
Fig. 7 is a circuit diagram showing a half
the present invention are similar to those of the
devices of my copending application entitled 25 section of a confluent type filter illustrating the
'-‘Pipe antennas and prisms,” filed March 1, 1941,
manner of using the electromechanical driving
Serial No. 381,236.
elements;
The object of the invention is to provide an
Fig. 8 is a fragmentary side view of the hull
efficient low frequency submarine projector or 30v of a ship showing the placement of the radiator
hydrophone which may lbe used for transmitting
in relation to the water line;
and receiving signals in a range where condi
Fig. 9 is a schematic circuit diagram showing
tions are more favorable than for the ordinary
how a plurality of radiators are connected in a
devices used for this purpose.
network with a plurality of filters to produce a
In accordance with the present invention a 35 prismatic effect;
submarine projector or hydrophone is formed of
Fig. 10 is a schematic circuit diagram showing
spond to the several frequencies of the spectrum
only when they approach the device at particular
respective angles, differing for each frequency.
The prismatic characteristics of the devices of
20
Fig. 5
Fig. 6
tionship
tal of a
a mosaic structure of piezoelectric crystals in the
how unidirectional amplifiers may be used in the
network of Fig. 9;
form of a thin blanket of considerable area at
Fig. 11 is a circuit diagram showing a circuit
tached to the hull of a ship. Such a blanket
consists of a plurality of narrow vertically dis 40 arrangement by which the amplifiers may be
pointed in one direction or the other as the
posed units connected in an electrical network
by which a prismatic effect may be achieved
crystal devices are to be used as radiators or
hydrophones;
and including amplifying means adjusted to
suppress secondary lobes. By way of example,
such a blanket may be of the order of three
feet in height, seven and a half feet in length
iinite cylinder;
and an inch and a half in thickness.
Each of the said units consists of an array
Fig. 13 is a pair of graphs showing funda
mental constants of a ¢iä-degree X-cut Rochelle
of bimorph crystal structures of a size and shape
best suited for the frequency range desired.
Such a plurality of crystals are electrically con
nected in parallel and physically housed in a
single container whereby in form each unit ef
salt crystal vibrating in flexure; and
Fig. 14 is a pair of graphs showing the eiiiciency
fectively consists of a long, narrow and thin
strip.
A feature of the invention is a hydrophone
consisting of a blanket-like structure comprising
a plurality of crystals divided into groups, each
group being connected into an electrical network
providing means for achieving a prismatic eiïect
Fig. 12 is a graph showing the result of cal
culations of the radiation impedance of an in
of conversion of a bimorph Rochelle salt pro
jector used at low frequencies. The solid line
graph shows th'e projector designed as a ñlter cir
cuit and the dotted line graph shows an alterna
tive wide band low efficiency design.
This disclosure sets forth a method for obtain
ing an eñìcient low frequency projector or hydro
phone which uses ‘l5-degree X-cut Rochelle salt
crystals in the form of a bimorph unit. Calcula
60 tions indicate that such a unit will cover a fre
2,405,226
3
4 ,
_minalwofu the> device andthe plating of the inner
¿surfaces Aare connected together andjconnected
quency range from 2750 cycles to 6000n'cyc1eswith
better thanv a 50 pery cent efficiency ofconversion.
to conductor I2 which forms the other terminal
As shown, the outer surfaces are
electrically connected to the frame but it will be
tal, it is possible to cover the frequency range
from '700 cycles to 7000 cycles with a 10 per cent¿`-' Í' understood Ythat the device may easily be com
" pletely insulated from the frame. In the com
eñìciency of conversion.
By resonating the static capacity at a lower fre
quency than the reso-nant frequency of the crysì-_v-4 » » of the device.
A low frequency radiator of this sort/can be`
used as an element in a prism type projector and
receiver for submarine location. Due :to thev low
- plete unit consisting of a plurality of crystals the
il electrical-connections of such terminals are in
14o ,multipla
frequencies possible, the medium will have less
'sow that-each radiator will have two
terminals.
v
-On th'e radiating or upper side, the chamber
between the crystal and the rubber Vdiaphragm I3
is filled with castor oill I4, which `conducts the
tances and with a greater certainty. Such a
projector also h'as the advantage that on account 15 vibrations from the crystal to the rubber dia
phragm, which in turn conducts the vibrations
of the lower frequency a pulse sent out from'the
to> the seawater.` vOn the other side ofv thecrys
searching ship will not> be as easily located by a
tal is an air chamber I5 whichintroduces a low
Vimpedance on the crystal. [Since the tWo sides
In the low frequency range from v1000 to 6000
attenuation and less refractivitys and hence it
is possible to locate a submarine at greater dis
submarine.
'
A_
K
"
.
of the chamber >arein seriesin the equivalent
cycles, it is diñîcult to obtain a projector or hy
drophone which will radiate .or` pick up. sound
electrical circuit, all >of the energy will be trans
with a good efficiency. Magnetic projectors made
ferred to the seawater sideandnone to theair
in this range have an efficiency of lessthan 1 per
side. When the radiator is 'lowered intoV the
water, the- air chamber is compressed but main
cent and, furthermore, have a small power Vh'an
dling capacity. The ,device of the present in~ 25 tains an equalizing pressureon the crystal sur
face and prevents the crystalfrom being bent.
vention is a projector or pick-up devicel using
In order to prevent the leakage of airthrough
bimorph Rochelle salt crystals capable of radi-y
the rubber diaphragmV I I, lathin metal diaphragm
ating a wide band of frequencies> efficiently and
with vconsiderable amounts of power.- '
g .' _i Y
9 is soldered to the metal frame 5 on both sides
'.
In form, the radiator consists of a longY strip,
by way of example, '7 to 8 centimeters widegßfto
4 centimeters thick and several feet long. Inthe
l30
.of the chamber. In order to prevent the leakage
of castor oil to the crystal .a similar thin metal
diaphragm I!) islsoldered to the frame part 4. In
assembling the unit'the crystal is ñrst glued to
drawings, Fig. l illustrates how a plurality of
»the lower steel frame part 5. 'I‘he upper part 4
such radiators may be attached to the _external
surface of the hull of a ship. _ _The same showing v3.5 is then screwed down to the lower part 5 and
glued to the upper surface of the crystal. rI'heis made in Fig. 8Y to illustrate'the 'position Vof the
lchamber- isvthen filled vwith castor oil and' the
plurality of radiators with respect -to therwater
upper rubber diaphragm 'is screwed'in place. It
`line. In Fig. l, each radiator comprises- a frame
I housing a plurality of bim'orph crystals' 2; in
will v’be noted that aV thin strip of rubber I6 be
dicated by a plurality of horizontal linesf YThe .4.0 tween the upper and lower metal frame parts >_4
and 5 lprevents sea water Vfrom coming into the
various units may be secured tothe surface _of
- crystal chamber. This is crushed dcwv'nY until a
the hull of the ship in any convenient manner,
metal-to-metal contact is made between the two
such', for instance, _as by a plurality of.Y clamps 3
parts 4 and 5 of the frame.
l
'
,
'
which may be loosened and rotated'to allow the
removal and replacement'of anyone unit, at a Á; ,
time.
-
Such a unit can be used as an efficient pick-up
device having a directivity normal to the length
thereof but no directivity along other directions.
By mounting a number of `such radiators'side by
side, attached directly to the ship’s hull _and conT
.5,0
When it is desired to have the pick-up insen
sitive to longitudinal waves in the metal frame,
as would be the; casey if the projector is mounted Vin the ship’s frame, the construction shown in
Fig. `3 may be used. For this case the crystal
is 'surrounded on both sides by oil chambers which
have small interconnecting holes which allow
nected to a suitable filter or> phase shifter a
theloil to flow _at a- slow rate from one chamber
prism-type projector and hydroph'onevcan be ob
to therother. " In this construction there is a bot
tom frame member Il' and an upper frame mem
ber I8. A thin metal ydiaphragm I9 is soldered
tained capable of workingrin theì low frequency
range. Due tothe lower attenuation and `_re'fraction of the medium for such- frequencies the
range of such a device may be larger than »for the
ultrasonic type of radiator. Furthermore,_ the
position of a ship sending out a low frequency
pulse is not as easily located by a'fsubmarine
unless it also has a large receiver capable of
working to low frequencies.
Y
'
'
-to the lower frame member I'I and the crystal
of two’slabs 2l) and 2| is clamped between the
frame members. The chambers between the
rubber diaphragm‘VZ-E and the crystal 2| and the
crystal 20 and the metal diaphragm I9 are ñlled
with castor oil. An air chamber is provided be
tween the metal diaphragm I9 and the metal
- ï
On accountof the birnorphtype 0f construction
backing plate 2'3. Small by-pass holes 24 and
25 are provided to allow communicationbetween
used, such a device mounted in'fthe side of va
ship will not pick up the structural noise propa 65 the two chambers 'filled with castor oil. At very
gated >through the frame of the ship.`
‘
'
rapid frequencies these small openings act'like
Onerform of the low frequency projector is
choke coils' and do notV allow a rapid interchange
shown in Fig. 2. Y It consists of a steel framework
of oil from one chamber t'o _the other. AtV a _high
water pressure, the rubber diaphragm is pressed
comprising the elements 4 and 5 which, when as
sembled in any convenient manner, securely h'old 70 in and more oil flows to the back oil chamber
the bimorph crystal. This crystal consists of two
slabs of crystals 'I'and‘ 8, plated ontheir sur
facesgwi‘th conducting material. The conducting
causing the air chamber to compress. 'In lthis
way no static pressure acts on the crystal. -When
a longitudinal vibration actuates the frame of
the projector approximately'equal pressures are
surfaces of the outer faces of the crystal are
connected together and form one electrical ter 75 generated in the two Oil chambers on each side
2,405,226
6
5
of the bimorph crystal.
radiation resistance and reactance for the sphere
and piston do not differ appreciably. Hence, We
are justified in assuming that the radiation re
As a result, since the
crystal is responsive only to unbalanced pressures,
no voltage will be generated by such a vibration.
sistance and reactance of a rectangle a half Wave
Calculation of radiation eûiciencies
The equivalent circuit of a bimorph crystal of
this type has been worked out for a unit which
is supported on the two ends but is free to bend.
This corresponds closely to the case considered
here since the glue will prevent the ends from
moving but is not stiff enough to keep them from
bending. The equivalent circuit as shown in Fig.
4 relates the input voltage and current into the
length long or greater over the frequencies of
interest will have the same resistance and re
actance as a cylinder having the same diameter
as the rectangle is wide. This results in a radia
tion resistance of the right order of magnitude
10 to work well with the impedance of a bimorph
Rochelle salt crystal.
The most advantageous type of crystal for this
use is a ‘L5-degree X-cut Rochelle salt crystal.
crystal to the average pressure and volume Ve
Although it cannot radiate as much power as a
locity over the surface of the crystal. In this 15 llô-degree Y-cut crystal, it has a higher electro
equivalence Co is the static capacity of the crys
mechanical coupling Which results in a consider
' tal, CivrVV the acoustic compliance of tne'crystal
ably :wider frequency range than can beradiated "
efficiently with a ‘l5-degree Y-cut crystal. Fur
electrically short-circuited, i. e.. the ratio be
tween the average pressure over the surface to
thermore, on account of the increased area of
the time rate of displacement of the crystal sur 20 such a radiator, the amount of power radiated
face, and M is the effective inertance of the crys
per square centimeter can be less. In a bimorph
tal. In centimeter-gram~second electrostatic
type of crystal, the properties do not vary as
units these quantities have the values,
much as for a longitudinal crystal and hence the
temperature eifect will not be as large. For these
reasons the ‘l5-degree X-cut crystal is here ern
Cu
ployed.
With this crystal the values of the constants in
centimeter-gram-second units are:
30
(l)
where l, Zw and Zi are respectively the lengths,
width and total thickness of the bimorph crystal,
K is the longitudinally clamped dielectric con
stant of the crystal, Y0’ the value of Young’s
modulus of the short-circuited plated crystal, p
the density of the crystal and D a function of
the piezoelectric moduli.
The complete equivalent circuit for the crys
tal used on a radiator is shown in Fig. 5. The
impedances on the two sides of the crystal are
effectively in series. On the non-radiating side
the impedance will consists of the inertance of
the oil chamber in series with the compliance of
the air chamber. This compliance is so large
compared to the compliance of the crystal that
it can be neglected. On the radiating side the
elements consist of the inertance of the oil charn
ber and the radiation resistance and inertance
of the medium.
For a circular source the re
sistance for small apertures increases propor
tional to the square of the frequency, but for a
long thin source it is to be expected that the re~
sistance would vary more nearly proportional to
the frequency. This has been ooniirmed by cal
culations on the radiation resistance of infinite
and ñnite cylinders vibrating radially. Such cal
culations show that if the length of the cylin
der is greater than half a wave-length at all fre~
quencies concerned, the resistance and reactance
of a radiating cylinder vary as shown in Fig. l2.
The dotted line lshows the multiplying factor
plotted as a function of wR/c, to correct the ra
diation resistance for the effect of fmite length,
where w=21rf; a=radius of cylinder; lzlength
of cylinder; A: wave-length; p--density of water;
and C==velocity of sound in water.
We are interested primarily in the radiation
resistance and reactance of a pulsating rectangle
in an infinite balile. However, comparison be
tween radiating spheres and radiating pistons in
baiiles shows that if the ratio of the diameter to
the wave-length is less than two tenths, the 75
(2)
when Y0 is the value of Young’s modulus for an
unplated crystal. Yo', the value for the plated
and short-circuited crystal, is given by
(3)
when
the clamped dielectric constant, is as
shown in Fig. 13. With this value of K the eiïec
tive Young’s modulus for a plated crystal is as
shown in Fig. 13 as a function of temperature.
Since most of the projectors are worked below
18° C., we can take as rough values
Yo'=2.2 >< 1011; K=150
(4)
By way of example, let it be assumed that it
is wished to radiate a band of frequencies centered
around 4000 cycles. It is assumed that 6 centi
meters is about the longest ‘l5-degree X-cut
crystal that is commercially feasible. The
resonant frequency of the crystal in air will be
f:
1
='.455l, [Xi
(5)
In water, however, we add masses due to the water
load and the Weight of the oil in the chambers.
If We make these chambers a total thickness of
.5 centimeter on a side or Ztl-1.0 centimeter, the
added inertance due to the oil will be
1.10
_i
The added inertance ofîl_wtheoìlb-_Zlw
water as determined
from Fig. 12 will be
u., 21r><400o _ u.,
( )
_ Actually an allowance of B/Zlw is made since the
piston type usually has more added mass than
the cylinder type. Hence, the total inertance
added to the inertance of the crystal should be
Mw= í
zz.,
(8)
2,405,226>
7
8
is then a half section of a coniiuent type which
The resonant frequency will then be '
has the element values
f =
i
:.4551,
R 21a/m
1
l2
p
'
-
v- -
(9)
1 +3.?
p f
Inserting the values
Yo'=2.2><1011; p=1.775
this becomes
10
_1.6>< 105it
fRz2
1
1+1.83/l,
(lo)
If the band is centered at 4000 cycles, the resonant
frequency of the crystal should be 4000 cycles.
Taking the ratio of Cn to C1, and the product
Assuming 1:6. centimeters and solving for Zt, we
ñnd
175:1.34 cm
.L1C1,we have
_
_
_
(11)
This total thickness would be made up of two
oppositely poled crystals, each .67 centimeter 20
thick.
With these values, the constants of a crystal
Solving the ñrst equation, using the value 3.17
bimorph unit 1 centimeterrwide, 6 centimeters
for Cri/C1, We find
long and 1.34 centimeters thick will be
25
C0==214 c. g. s. units=238 mmf.
(12)
f2=1ye`8f1
<18)
CM=1.47 >< 10-9
M=1.08
Y
_
The second equation shows that the crystal
Y
rp=2.15><105 c. g. s. units=.226 in practical units.
The radiation resistance at 4000 cycles, accord
ing to Fig. l2, will be about
resonance occurs at the mean frequency of the
30 pass band which in this case is 4000 cycles.
Hence, for this case
R=.58 pc=8.7><104 acoustic ohms per square
cm.
,fr-:3040 cycles
(13)
(19)
fz=5270 cycles
In acoustic impedance units we have to divide 35
The image impedance at the main frequency
this by the cross-sectional area which is 6 Square
should be
centimeters, so
R=1.45 >< 104V ohms, acoustic resistance.
(14)
Zo=21r(f2-f1) L1=2.96X105 ohms per unit _length
(20)
If we take these quantities through the elec 40
tromechanical transformer, we will have electri
cal quantities as shown on Fig. 6, having the
values for a crystal 1 centimeter Wide
00:238 mmf.
L =M
l
/qö
2:21.?, h
4
‘
elmes
(
15
which agrees Well with the
_
ing for the current in the output of the network
of Fig. 7 and comparing that to what would
)
be obtained by the use of a perfect transformer
between the input resistance RA and the _output
‘í’
50 radiation resistance RB.
The filter-type structure is the most eiiicient
Q_
equation
This results v1n the
Y
' NRA-RB
_
Y
_
RA
_
__
2
’ _ ;
(2i)
\/[R..+RB M001@ @213.00m @2130001 +[ w01 1 *do
'
_,
The actual loss in conversion from electrical
45 to mechanical energy can be calculated by solv
133:@ :2_84X105 Ohms
i
radiation resistance
as calculated hereinbefore .
i-aßLlo1 ._RARB(1-@L„co)]2
_
way to utilize electromechanical driving elements,
since the ñlter with matched impedance termi
nations is the device which will deliver to its out
If we insert the ñlter relations hereinbefore
stated in relation to Fig. 7, and let RA, the out-v
put impedance of the amplifier equal Z0 for the
put all the energy sent into it over the widest
ñlter, we have
_
Y
frequency range consistent with the elements of
where
which it is constructed. The Widest band ñlter
using the elements of Fig. 6 as part of the ñlter 70 mM =ZT1 = m =the mean frequency of the radiator
configuration is one using a series or shunt coil
to annul the static reactance of the shunt con
denser. For such a wide band it makes little
diiîerence which conñguration is chosen and so
Fig. 7 shows the use of a shunt coil.
The filter 75
A plot of this equation with Re taken from Fig.
l2 and
«ence-,226
10
'9
is then shown in Fig. 14. ‘As can be seen, the
efficiency of conversion does not drop below 6
decibles or 25 per cent from 2400 cycles tov 6000
hull of a ship, and .the change in direction is ob
tained by prism methods, the device becomes
practical.
As an example let us consider what can be done
-with a radiator working from 2.75 kilocycles to
6 kilocycles, as calculated previously. To get the
same directivity as at ultrasonic frequencies will
resonance, a somewhat wider band can be ob
require a radiator 6 wave-lengths long which at
tained as shown by the dotted line graph of
the mean frequency of 4000 cycles will be a
Fig. 14 at some sacrifice of efñciency of conver
sion. It can be shown that the best eñiciency 10 length of 225 centimeters or 7.4 feet. If we di
vide this up into long radiators which are .4 of
will be obtained by letting the right-hand terms
a wave-length apart at the top frequency of
of Equation 21 vanish when w2=wAwB is the reso
6000 cycles, this requires twenty-two strips each
nance of the coil and condenser, and we the me-1.0 centimeters wide. The length of the strips is
chanical resonance of the crystal and added
mass. This results in the relation
' '
15 determined by the directivity in a vertical plane.
A length of three feet would concentrate most of
1
r
the power in an angle 115 degrees from the
(23)
horizontal. Such> a blanket radiator 7.4 feet
where 1’ is the ratio of capacitances
long, three feet wide and approximately 1.5 inches
20 thick could be attached to the hull on each side
of the ship as shown in Fig. 8. On account of
cycles.
By separating the resonance of the electrical
coil with crystal capacity from th‘e mechanical
RARE-wAœBC'lCg-caAwBC'OZ
C1
the smooth surface, streamlining is obtained and
For this case the expression for the efficiency
becomes
a freedom from turbulent noise. Leads from each
radiator connect to a filter or phase shifting net
@_
'
_
2
2
“T «taie-(eared
aan[acera-air
(24)
As an example, let us take fA=1000 cycles, „lo work as sh'own in Fig. 9 for a listening system.
On account of the low power carrying capacity of
At the mean frequency of 2000 '
coils and condensers used in iìlters or phase shift
cycles, RB the radiation resistance for a crystal 1
ing networks it is desirable to place a power am
centimeter wide is
pliñer between each radiator and the filter as
RB: 1.72 >< 105 electrical ohms
(25)
shown in Fig. 10. By adjusting the gain of each
Using the same constants as in the examplel ' amplifier it is possible to compensate for the
loss in filter or phase shifting network and more
considered above, the best ampliñer impedance is
over secondary lobes can be suppressed by driv
RA=2.07><106 electrical ohms per centimeter , ing the middle segments harder than the' outer
'
width of crystal
<26)
40 segments. Since ampliñers are one-way devices
With these values, and taking Re from the curve
it is necessary to have the input connected to
of Fig. l2 the efficiencies of conversion in deci
the phase shifter and the output connected to
bels below perfect efiiciency of conversion are
the radiator when a pulse is sent and reversed
shown by the dotted line of Fig. 14. From 700
when a listening condition is desired. If the
cycles to 6500 cycles an efficiency of conversion 45 input and output impedances of the ampliñer are
averaging around 10 per cent is obtained with a
made the same, this can be accomplished by a
simple switching arrangement as shown in Fig. 11.
variation of about i4 decibels over this region.
On account of the large area and relatively high
Even if the power radiated by each unit is kept
fis=4000 cycles.
efficiency of conversion such a device would pro
down to the 0.1 watt per square centimeter ra
vide a more efiicient listening device than has 50 diated from other ‘i5-degree X-cut Rochelle salt
previously been obtained for his frequency range.
crystals, the power radiated from each strip will
To work -down to 700 cycles a device about 105
be 150 watts. For all twenty-two strips the total
centimeters or 3.5 feet long would be required.
power would be 3.3 kilowatts which is consider
This would have a receiving area of 630 square
ably more acoustic energy that has been radi
centimeters and would be able to deliver 5><10-'1 55 ated from ultrasonic projectors. This coupled
watts electrical power to a receiver when a pres
with the lower attenuation and lower refractiv
sure of 100 dynes per square centimeter was act
ity realizable at the lower frequencies, and the
ing on it. Since a telephone receiver has a
freedom from noise due to streamlining indicates
minimum power of about 4X l0“14 watts to reach
that submarines could be located at farther dis
audibility, this would represent enough power to 60 stances and under more exacting conditions for
operate the receiver without the need of an am
the low frequency radiator than for the ultra
pliñer. F01- such a hydrophone, the static ca
Isonic radiator. Such a system also has the ad
pacity of the crystals would be 25000 ccf, so the
vantage that on account of the lower frequency
additional capacity put on by a cable would be
the direction of a pulse sent out from the search
small, and could be neglected. The electrical im 65 ing »ship will not be as easily located by a subma
pedance of an amplifier or receiver to work With
rine.
the unit should be about 20000 ohms.
What is claimed is:
Use of low frequency projector in a. prism type
detection system
In order to make full use of the lower attenu
ation and refractivity of the lower frequency
range, a radiator sufficiently large to obtain a
good directivity may be used. Such a radiator
1. A sonic device for use as a submarine pro
jector or hydrophone consisting of a blanket
70 like array of vertical and horizontal rows of co
ordinately arranged piezoelectric crystals for
placement on the external surface of the hull of
a ship, 'said crystals of each vertical row consti
tuting a unit, an electrical network for connect
is too large to turn manually. If, however, it is
used in the form of a thin skin attached to the 75 ing said array of crystals to transmitting and re
11
12
ceiving apparatus, said network including phase
shifting circuits, each said unit being electrically
said units by' said phase shifting circuits where"
by a prismatic effect is secured, an vampliíierlfor
separated from other of said units by said phase
shifting circuits, and each said crystal compris
each said unit, the gains of the ampliiiers being
higher for the middle units and lower for' the
~ ing a bimorph structure constructed and arranged
end units whereby secondary lobes are- sup
pressed, means for directively pointing said .arn
plii'lers in accordance with the directionof use
.
.
to respond to frequencies within the audible
range.
'
2. A sonic device for use as a submarine pro
'jector or hydrophone consisting of a blanket-like
arrayl of Vertical and horizontal rows of Coor
dinately arranged piezoelectric crystals for place
of said device, and each said crystal comprising
a bimorph structure constructed and arranged
10 to respond to frequencies within the audible
range.
'
`
,
4. A sonic device for use as a submarine pro
ment on the external surface of the hull of a
jector or hydrophone consisting of a blanket
ship, said crystals of each Vertical row being
like array of piezoelectric crystals in vertical
connected in multiple, housed in a single con
tainer and constituting a unit, an electrical net 15 and horizontal rows, the crystals of 'each verti
cal row being connected in multiple and acting
work- Vfor connecting said array of crystals -to
'transmitting and receiving ap-paratus, said net
as a unit, an electrical line including a series of
work including phaseshifting circuits, each said
unit being electrically separated from other of said
phase shifting networks with a connection to
' said'unit, the gains of the amplifiers being higher
line will cause correspondingly diiïerent fre
each said Vertical row of crystals made to a point
units by said phase shifting circuits whereby a 20 in said line between succeeding networks, where
by difl’erent frequency currents connected to said
prismatic eiîect is secured, an amplifier foreach
for the middle units and lower for the end lunits
whereby secondary lobes are suppressed, Yand each
said crystal comprising a bimorph structure con
structed and arranged to respond to frequencies
within the audible range.
'
3. A sonic device for use as a submarine pro- ,
jector or hydrophone consisting of a blanket
like array of vertical and horizontal rows of co
quency signals to be transmitted in correspond
ingly different directions or whereby incoming
signals may be received from correspondingly
different directions in accordance with theirn _fre
quency.
Y
5. A submarine projector or hydrophone con
sisting of a plurality of bimorph crystals re
30 ’ sponsive to frequencies within the audible range,
means coordinately arranging said crystals in a
sheet of Vertical and horizontal rows, means
whereby the crystals in each Vertical row are con
of a ship, said crystals of each Vertical row being
nected in parallel and comprise a unit, means
connected in multiple, housed in a single con
. tainer and constituting a unit, an electrical net 35 whereby the various units are connected to a
-ordinately arranged piezoelectric crystals for
placementv on the external surface ofthe hull
work for connecting said array of crystals to
transmitting and receiving apparatus, said net
‘ work including phase shifting circuits, each said
1 unit being electrically separated from other of
transmission line and phase shifting net-works
interposed in said line electrically between each
of said units to produce a prismatic effect.V
"
WARREN P. MASON.
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