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Патент USA US2411551

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Nov. 26, 1946.
- ‘w. P. MASON
Filed Aug. 19, 1941
FIG. 24
FIG 6'
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‘ ’ 7%1{ ATTORNEY
Paienieo‘l- “Nov. 2d. lddd
, __
Rapm'rmo SYSTEM
Warren P. Mason, West Orange, lil. .L, assignor to
Bell Telephone Laboratories, Incorporated, New
York, N. Y., a corporation of New York
Application August 19, 1941, Serial No. 407,457
.4 Claims. (Cl. 177-386)
' 2
This invention relates to improved directional’
compressional wave radiating systems of the
type of- loudspeaker such as, f1
disclosed in‘ United States Pat‘
sued May 7, 1929, to A. I. Abral
driving mechanism is not show
it would unnecessarily compli
multielement type. More particularly it relates
to radiating systems in which the energy is dis-:
tributed nonwunlformly over the elements of the
radiating system to reduce the relative strength
Such mechanisms are well knov
are not involved in systems of
of secondary radiation lobes with respect to the
main radiation lobe.
A-principal object of the invention is therefore
will become apparent presently.
For radiating surfaces of the
to produce directional radiating systems having
relativelysrnall secondary radiation lobes.
. by member ill of Fig. 1, characte
Another object of the invention is to reduce
well known that the directional
will be substantially as indicatel
acterized by a main lobe i2 01
particle velocity over the surf:
secondary lobe radiation from multicrystal radi
ating systems.
directivity and secondary lobes
small but not negligible strengi
appreciably in angular directivi‘
A further- object is to reduce secondary lobe
radiation from multiunit magnetostrictive ra
diating systems.
Other and further objects will become apparent
lobe. '
during the course of the following description and
For directive systems in whicl
in the appended claims.
directive indications‘ are desired
of radiators of the type illustrat
been found to be objectionable s
is sometimes misled byminor lol
tains false directive indication:
It is well known in the art
rl‘he systems of the invention will be more read
ily understood from the following description of
illustrative embodiments taken in conjunction
with the accompanying drawing in which:
Fig. 1 illustrates a radiating element of sub-v
stantial surface area uniformly driven;
Fig. 1a indicates the directive radiating pattern
of the surface of Fig. 1;
Fig. 2 illustrates a radiating element of sub
member such as In of Fig. 1 unil
have a pattern of the type descri
gection with Fig. 1a and represe:
stantial surface area driven with straight line :
variation of intensity from zero intensity at the
ends to maximum intensity at the center;
Fig. 2a indicates the directive radiating pattern
of the surface or‘ Fig. 2;
Fig. 3 illustrates a radiating element of sub- 2
stantial surface area driven with sinusoidal
variation. of intensity from zero intensity at the
ends to maximum intensity at the center;
where his the length or width
is 21r times the frequency, v i
propagation‘ in the medium, 0 i:
ured between the direction of t
length of the radiator as show
Fig. 4 shows a radiating system comprising a
pressure at the angle a, an
plurality of piezoelectric crystals aligned to form 40 the
sure normal to the radiator. Tl’.
a multielement radiating surface, the driving
that if most of the radiation
electrode areas of said crystals varying from very
within i1° from the normal, ti
narrow areas for the outermost crystals to sub
be about 5'7 wave-lengths across
stantially complete coverage of the central crys~
Fig. 5 shows a radiating diaphragm of substan
plications would be inconvenie1
Also, secondary lobes will exi
tial surface area driven by a plurality of mag
(5-,)- cos 0) 2
netostrictive vibrators, the driving intensity
varying from small intensity at the outermost
vibrators to maximum intensity at the center 50 etc, whose values compared to
1 .3_
. 2
vibrator; and
37:13.5 db., 51717.9 (11)., n;
‘Fig. 6 shows a sound radiator of the multisec
tion wave ?lter type with energy radiation pro
The ?rst lobe is only 13.5 dei
vided from each section of the structure.
pared to the main one and ma
In more detail in Fig. 1 a member or diaphragm
tioned, introduce some di?icu
‘ I0 is assumed to be driven from position a to posi
tion b with uniform amplitude at all points there
A method for reducing secc
of. This may be accomplished, for example, by
respect to the main one is discu
the well known electromagnetic type of driving
2,225,312, issued December 17,
mechanism employed in the so-called dynamic 60 thereof, column 1, line 75 to r
As applied to the radiator of Fig. 1, this method
requires the particle velocity at the edge of the
similar types for piezoelectric
tive radiating systems, respect
radiator to be much less than that at the center.
'tric radiator frequently used C1
A distribution investigated, by way of example,
or an “array” of substantially
was one in which the particle velocity was zero at 5 salt crystals connected in pa
the edges and increased linearly to the center as
physically to present, substam
indicated for the diaphragm 22d of Fig. 2, dotted
radiating surface as represen'
M, as and lit of-Flg. 4;
lines a and b indicating the mode of vibration of .
For this distribution the radia—
tion patter-‘n
illustrated by curve 22 of Fig. 2a
and is given by the equation
In one oommon'form the rm
all ‘be mounted on a common b,
for example, could be placed l
crystals of Fig. 4 and have the
crystals cemented to it, ' the
crystals forming aradi'ating s
_;able area. An alternate com
would be to support all the cry
employ radiation from both to
or the crystals. The crystals 2
trically inparallel across the 4
Fer this distribution the ?rst minimum comes at
twice the angle as for the uniform distribution
of Fig. 1, but the secondary lobes are down com
pared to the fundamental by the values
20v later
To reduce the secondary lob
suggested above, we can use"
of ' crystals b1;
width of the electrodes, or plat
25 trodes are employed, so that s
the crystals it on the ends 1
To get the same sharpness requires a radiator
with twice the length, but all the radiation max
trodes, or plating areas, when
ima are down
as far in decibels as for the
in the center has its sides com
uniform radiator.
the electrodes, and intermedi
A radiator in which the secondary maxima are 30 electrodes of intermediate wid'
‘not down quite as far, but which requires only a
creasing with proximityto the
viding that the plating, or elec
50 per cent larger radiator to get the some sharp
(r) =41.c db., etc.
For this radiator the
same lengthras the crystals 2
particle velocity of diaphragm ‘it is substantially
very in width only, the force e:
ness is shown in Fig. 3.
zero on the two ends and has a sine wave dis-, 35 dividual crystal will be propor1
tribution of particle velocity between dotted lines
ing or electrode area and the di,
portional to the force since a]
similar. Hence, if the area of
' a and 1; indicating the mode of vibration of dia
phragm- 36. A sine wave distribution of energy
as applied to a multitube directive acoustic re
‘linearly from the two ends of
ceiver isdiscussed and analyzed in my above 40 center, the radiation pattern (
mentioned Patent 2,225,312 on pages 2 and 3
be obtained, whereas if the ares
or plating, is distributed accord
thereof; page 2, column 2, line 48 to page 3, col
curve with the maximum at the
umn 1, line iii. In the device of the patent the
zeroon the and crystals, the dis
areas of the respective tubes, or their ori?ces,
tion 5 will be obtained. vIn tl
are varied substantially in accordance with a
sinusoidal lawof variation. In this particular
plating areas should vary as law
instance the row of tubes is wound about itself
of the tubes of the acoustic de'
mentioned Patent 2,225,312 beg
to form a compact assembly so that‘ the tubes may
be more readily associated with a. conventional
column 2, line 47 as above poll
type of receivcreniicrophone and to facilitate the 50 ‘present application being the,
pointing of the'ossembly. For the type of radi
electric vibrators and a being
ator illustrated by Fig. 3 and the arrangement of
my patent just mentioned the distribution pat
tern is given by the equation
An alternative arrangement,
tenuator for each crystal, or ear
PM) l—~ (“:5 cos 0)
at a particular distance from '
array, would be to use crystals
trodes but to limit, by interposi
The first minimum comes when
suitable amounts, the energy to
tals to obtain an approprlatl
energy among them.
Fig. 5 shows onerway of obtaii
which is 50 per cent larger than that of Fig. 1, but
the secondary lobes have the values with respect 65 particle velocity distribution l
strictlve drive. For this cas
to the primary lobe of
cos 9>=§2Z
diaphragm 50 clamped on the
a number of magnetostrictive
‘Since the edges are clamped t
and the shape assumed by tl'.
This decreases the first secondary lobe with re 70 vibrating will be nearly that :
spect to the primary by 10 decibels at the expense
giving the radiation pattern sho‘
of widening the radiator only 50 per cent to re
The central magnetostrictive :
tain the same sharpness of the primary lobe.
course driven most strongly 1
Figs. 4 and 5 show two methods of realizing
56 progressively less strong
particle velocity distributions of the above and 75 all energy
distribution preferab
proportioning the windings of the magneto
strictive members as indicated in Fig. 5 or alter
natively by employing attenuators as suggested
above for crystal arrays. The magneto-strictive
members are connected electricalLv in parallel
across the output of an oscillator 58.
In Fig. 6 a sound radiator in the form of a
ing members similar to the crystal array 0! m.
4 could be employed without a diaphragm, or,
conversely, a plurality of crystals could be em
ployed in place of the magnetostrictive vibrators
of Fig. 5 to drive the diaphragm 50, sinusoidally,
and numerous other arrangements within the
spirit and scope oi the invention can readily be
devised by‘ those skilled in the art. No attempt
to exhaustively cover such arrangements has
here been made. The scope of the invention is
_ de?ned in the appended claims.
multi-section wave ?lter having sixteen sections
80, Si, 82, 83, at, 85, 88 and a1 (two sections on
opposite sides of the center of the structure be-,
ing assigned the same number) is shown.
the left end of the structure a plurality of piezo
What is claimed is:
1. A piezoelectric radiator comprising a plu
rality of substantially identical piezoelectric
crystals arranged in line, corresponding radiat
15 ing ends of the crystals lying in a common plane,
electric crystals 9". enclosed in a housing member
89, are employed to energize the structure and
a pair of electrodes on each crystal. the elec
trodes extending in every case the full length of
the crystals, the width of the electrodes on the
at the right end a member 88 of absorbing mate
rial is provided to absorb such energy as may 20 end crystals of the line being small with respect
to the width of the crystals, the width of elec
reach the right end of the ?lter.
crystals being progres
Each of the sections comprises-a cup-like mem
of the line is ap
ber of square cross-section, the cup bottoms 82
proached, the central crystal or crystals having
serving as diaphragms, coupling adiacent cavi
ties. Each section is provided with several holes 25 electrodes of greatest width whereby minor lobe
small portion oi the total energy
radiation from said array of crystals is substan
passing through the ?lter is radiated. The hole
2. Inreduced.
a directive radiating system a plurality
sizes are adjusted so that maximum energy is
of substantially identical piezoelectric crystals
radiated from the central sections 81 and de
aligned in parallel relation with particular
creasing amounts of energy from sections“, 85,
BI, 83, 82, 8i and Bil, respectively, in accordance 30 radiating ends of each in a common plane. the
electrode plating on each crystal extending the
with their respective distances‘ from the center.
full length of the crystal, the width 0! the plat
Because of attenuation and loss of energy by
ing varying from a small fraction of the width
radiation the sections on the right half of the
structure will have somewhat larger holes in 35 of the crystal for the outermost crystals to sub
stantially the full width or the crystal for the
order to radiate the same energy as'correspond
centrally positioned crystal, the variation in
ing sections of the left half of the structure.
plating area following a substantially sinusoidal
Again, the distribution of radiated energy may
vary from maximum at the central elements to
law of variation.
3._The radiator of claim 1 the electrode area
minima at each end in accordance with a straight
end crystals sub
line, sinusoidal, geometrical progression or other
stantially in accordance with a straight line law
law of variation depending upon the particular
performance desired.
of 4.variation.
The radiator of claim 1 the electrode area
The structure of Fig. 6, though of di?erent
form and proportions, is of the same general type ' varying from the central to the end crystals sub
stantially in accordance with a power series law
as that illustrated by Figs. 15, 16 and 1'1 of, and
described in, my copending application, Serial
No. 381,236, filed March 1, 1941, entitled “Pipe
antennas and prisms.’or magnetostrlctive vibrat
Obviously, an array
of variation. \
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