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ea. 31, 1946.,
Filed July 17, 1941
5 Sheets-Sheet l
Dec. 31,1946.
Filed July 17, 1941
5 Sheds-Sheet 2
Dec. 31, 1946.
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Filed July 17, 1941
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Dec.‘ 31, 1946.‘
Filed July-l7, 1941
5 Sheets-Sheet 4
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Filed July 17, 1941
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Patented Dec. 31,1946
Albert B. Hurley, Huntington, N. Y.
Application July 17, 1941, Serial No. 402,793
. 7 Claims.
This invention relates to the acoustic treatment
of ceilings and walls for purposes of sound con
The primary object of my invention is to gen
erallyimprove the treatment of walls for noise
absorption, or improved acoustics, or sound con
trol in general.
Another general object is to
provide an improved tile or board for that pur
The science of sound control has undergone
considerable development in recent years, and
‘a number of companies manufacture tile or board
of various kinds for this purpose. Some of these
materials are matted wood ?bre, porous gypsum,
arti?cial stone using expanded mineral aggre
gate, mineral ?bre or rock wool in pad or blanket
form, baked rock wool and clay mixture, asbestos
(01. ISL-33)
this purpose a number of different expedients
may be employed, such as the provision of aper
tures in a thin tile made, for example, of enam
elled sheet metal or plastic, or the provision of
holes (round or elongated slots) part way
through or all the way through a relatively thick
porous tile made, for example, of wood pulp, mat
ted wood ?bre, porous gypsum, or the llke.
Where the tiles are to be secured to furring strips,
as is usually the case, a space is inherently pro
vided in back of the vibratile diaphragm. In
some cases, particularly with a thin perforated
tile, it may be preferred to place sound absorbing
pads or blankets made of a loose ?brous material
such as mineral wool, in this space between the
furring strips, but such pads are not at all essen
tial with my invention, In rarer cases the tile
may be cemented directly on a wall without furr
?bre appropriately cemented with or without the
.admixture of other materials, etc. Some of these
ing strips, but in that case it should be provided
products rely solely on the porosity of the ma 20 with peripheral ledges, which are either added
terial, while others additionally provide holes in
to the tile or molded integrally with the tile, in
the material in an e?ort to improve the sound
order to provide the necessary space in back of
the diaphragm.
If the results obtained by the use of these ma
A further object of the invention is to obtain
terials is studied, it will be found that the sound
a more level response for the absorption of low
absorption ef?ciency is substantially-greater for
frequencies, and for this purpose a number of
higher audible frequencies than for the low fre
tiles may be made, each having a diiferent natu
quencies. One primary object of my invention
ral resonance frequency. In one aspect, this ob
is to improve the efficiency for low frequencies.
ject of the invention concerns provision of con
With this object in view the tile or board is pro 30 venient methods of controlling the natural vibra
vided with peripheral cuts which separate the
tion frequency of the tile. The di?erent fre
same into a marginal mounting portion and a
quency tiles may be applied to a wall or ceiling
vibratile center or diaphragm portion located
in appropriately staggered arrangement. In some
‘cases, a predominant number of tiles of a par
ticular frequency may be used, depending on the
acoustic problem raised in any particular in
within the marginal mounting portion. These
peripheral cuts operate to weaken the connection
between the diaphragm portion and the marginal
portion in order to increase the ?exibility of the
connection, thereby facilitating vibration of the
In accordance with a further feature of my
diaphragm portion, This enhances the dampen
invention, multiple diaphragms may be provided
ing or absorption e?iciency of the board for low 40 on a single board. Thus a large board may be
frequency sound.
An ancillary object of my invention is to par
ticularly increase the ?exibility of the connec
sub-divided into, say, four diaphragms, each di
mensioned as though formed in a board only half
as long and half as wide as the actual board.
tions, or as I term the same, the “bridges” be
This reduces the amount of labor attendant upon
tween the marginal and diaphragm portions. 15 nailing up the boards. In other cases a small
With this object in view, I provide auxiliary cuts
diaphragm may be formed at the center of a
at the bridges transverse to the peripheral cuts,
thereby lengthening and so increasing the flex
ibility of the bridges. When dealing with tiles
of ordinary square dimension, it is most con
venient to form the bridges by means of diagonal
cuts at the corners of the tile.
A further object of my invention is to utilize
large diaphragm, thus providing a diaphragm
resonant to one low frequency at the center of
a larger diaphragm which is resonant to another
low frequency,
Acoustic tiles having a diaphragm action are
not broadly new, one such tile being made, for
example, by Heerwagen Acoustic Decoration
known methods of improving the sound absorp
Company. However, such diaphragm tiles as
tion‘e?iciency for high audio frequencies and for 55. have been made heretofore have been delicate
Fig. 21 shows av modi?cation having through
holes and an elongated diagonal bridge;
Fig. 22 is a modi?cation having through slots;
in structure and di?icult to apply, and while they
may be helpful in eliminating some particular
rumbling reverberation or booming sound, are
Fig. 23 is a modi?cation using biased or sloping
' little or not at all helpful for sound absorption
of high audio frequencies. They su?’er from the
serious limitation of being useful only for low
frequencies. Thus, while acoustic tiles are al
ready available for high or low frequencies alone,
gular slots;
their e?iciencies fall 01? very sharplylfor low or
having through slots and perforations;
Fig. 24 shows a modi?ed arrangement of an
Fig. 25 illustrates a thin metal or plastic tile
high frequencies respectively. With my inven 10
Fig. 26, is a similar view showing a thin tile
tion, both low andhigh frequencies may be taken
having slots;
care of.
Fig. 2'7 shows how the thin tiles may be mounted
on furring strips;
Fig. 28 is a modi?cation in which the space be
To the accomplishment of the foregoing and
such other objects as will hereinafter appear, my
invention consists in the acoustic tile features
and their relation one to the other as herein
after are more particularly described in the
tween the furring strips is occupied by blankets
or pads of mineral ?bre or rock wool or like ab
sorbent material;
Fig. 29 illustrates a modi?cation using crossed
speci?cation and sought to be de?ned in the
claims. The speci?cation is accompanied by
drawings, in which:
furring strips;
Fig. 1 is a perspective view of a thin metal or
a thin metal or like hard-surfaced tile secured
plastic board showing the peripheral cuts to facil
itate vibration;
directly to a porous pulp tile;
Fig. 31 is a similar View in which the porous tile
is slottedin registration with the perforations in
Fig. 2 is a fragmentary view of one corner of
a cast tile or pulp tile with a blind slot or groove
the metal tile;
Fig. 3 is a similar view, but showing a board
having a through out and an elongated bridge;
Fig. 4 is a similar view showing a thin metal
Fig. 33 is a bottom plan view of the same;
Fig. 34 is a fragmentary section drawn to larger
scale and showing a modi?cation;
Figs. 35, 36, and 37 are fragmentary views
showing how the resonance frequency of a tile
may be varied by changing the length of the
bridge or the width of the bridge, or'both;
tile with a diagonal bridge weakened by a longi
Fig. 6 is a similar view showing a tile with
through cuts and a modi?ed bridge;
Fig. 7 is similar, but with a further modi?cation
of the bridge;
the porous tile, said section being taken approxi
mately in the plane of the line 32-32 of Fig. 33;‘
Fig. 5 is a similar view showing a cast or pulp
tudinal cut;
Fig. 32 is a section through a modi?cation in
which the metal tile is spaced somewhat from
or plastic tile with a diagonal bridge;
Fig. 30 shows a laminated material made up of
Figs. 38, 39, and 40 are sections taken longitu
Fig. 8 is a section taken in the plane of the line
dinally of the bridge (as in Fig. 8) and show how
8—8 of Fig. '7, and illustrates a method of fur
the resonance frequency of the tile may be
ther weakening or improving the elasticity of the 40 changed by changing the thickness of the bridge;
Figs. 41, 42, and 43 are sections through a resil
Fig. 9 is a similar section, but showing a modi
ient bridge, and show how the resonance fre
?cation in which the bridge of a relatively brittle
quency of the tile may be changed by varying the
cast tile is strengthened by means of an embedded
length or the thickness of the resilient bridge, or
as. m'
metal reinforce;
Fig. 10 shows one corner of the upper side of
Fig. 44 shows how a smaller diaphragm may
be formed in a large diaphragm;
a board in which the diaphragm portion is fully
separated from the marginal portion but con
nected thereto by means of a spring bridge;
bridge strengthened by flexible means cemented
Fig. 45 shows how differentfrequency tiles may
be staggered when using tiles of, say, ?ve di?er
ent frequencies;
Fig, 46 shows how a‘tile of one frequency may
be multiplied relative to the others, depending
Fig. 11 shows a cast tile having a diagonal
Fig. 12 is a section taken in the plane of the line
on the needs of any particular installation;
l2-l2 of Fig. 11;
.Fig. 47 illustrates the use of tiles of only two
Fig. 13 is explanatory of how the boards of my 55 frequencies, one of these being used more than
invention may be secured to furring strips;
the other to ?ll the needs of a particularin
Fig. 14 illustrates how the marginal portions of
a board may be thickened if the board is to be ce—'
Fig. 48 shows how multiple diaphragms may
merited to a wall;
be formed on a single large board to facilitate
Fig. 15 illustrates such boards cemented to a 60 installation of the boards;
Fig. 49 shows how holes (to aid high frequency
absorption) may be provided all over a tile. in
Fig. 16 shows how the boards may be provided
with integrally thickened marginal portions;
cluding even the marginal portion thereof;
Fig. 17: illustrates boards of this character ce-' 65
merited to a wall;
Fig. 18 is explanatory of the fact that the vari
ous boards here illustrated, while shown with
simple square edges, may be interlocked by ap
propriate known joints;
Fig. 19 shows how the diaphragm portion of a
thick porous board may be provided with blind
Fig. 20 is a similar view showing how the board
may be provided with blind intersecting slots;
Fig, 50 shows a partially cut away composite
tile in which a thick vibratile diaphragm is con
cealed by a highly perforate thin metal cover
plate; and
Fig. 51 is a fragmentary section drawn to en
70 larged scale and taken approximately in the plane
of the line 5 |-—5l of Fig. .50.
Referring to the drawings, and more particu
_larly to Fig. 1, I there show a board or tile I2
made of thin hard material.
It may, for ex
75 ample, be made of metal appropriately painted
or enamelled.
It may also be made of a thermo
and dividing the same in effect into two narrower
plastic material, such as Bakelite or other sim
ilar plastics, from which boards or panels are
Fig. 6 illustrates a thick porous tile, the dia
phragm portion 10 of which is connected to the
made by impregnating fabric, paper, or wood
In accordance with my invention the
marginal mounting portion ‘l2 by means of a di
tile is provided with peripheral cuts l4, I6, I 8,
agonal bridge 14 formed by diagonal slits 15.
These, as well as the main cuts 18, pass all the
way through the material. In this case the di
and 20. These divide the tile into a marginal
mounting section or portion 22 and a center or
diaphragm section or portion 24. The marginal
agonal cuts 16 extend outwardly from the periph
mounting portion may be secured to furring strips 10 eral cuts 18.
or the like, by means of nails, screws, or other
In Fig. '7 the diagonal cuts 88 extend inwardly
suitable fasteners. Because of the peripheral
and outwardly of the peripheral cuts 82, thus pro
cuts the diaphragm portion 24 may vibrate
viding an elongated bridge 84 which yieldably
readily relative to the marginal portion. This
connects the diaphragm portion 86 to the mar
vibration under the impact of low frequency 15 ginal mounting portion 88.
sound waves serves to dampen and absorb the
Fig. 8 illustrates how the diagonal bridge may
sound waves. The cuts are not continuous, the
be further weakened for freer vibration, partic
interruptions therebetween leaving rigid and
ularly when dealing with a thick tile or board.
?exible spaced connections 26 which may be
In Fig. 8, which is a section taken longitudinally
termed “bridges.”
20 of the bridge 84 in Fig. 7, it will be noted that the
Referring now to Fig. 2, I there show one corner
bridge portion 84 is cut away at the back, as is
' of a tile or board which may be made of a suit
indicated at 90.
able porous material. Known commercial ma
terials may be used, such as those made by the
This constitutes another means
for controlling the vibration of the diaphragm
portion, particularly when dealing with thicker
Celotex Corporation which makes Acousti~Celotex 25 or stiffer materials.
out of perforated ?bre, Mu?ietone out of cast
Some materials, such as cast gypsum, may prove
porous gypsum, Calicel which is an arti?cial
porous stone made out of expanded mineral ag
gregate, and Absorbex made out of matted wood
?bres. Other suitable materials are made by 30
to be troublesome because of their brittle or
frangible nature. Thus with tiles having 9, dia
phragm portion connected to the marginal por
tion solely at the corner bridges, di?iculty may
Johns-Manville Corporation, who make Perma
arise because of breakage of the bridge during
coustic out of baked rock wool and clay; Sponge
shipment or handling. This difficulty may be
coustic out of asbestos ?bre, natural sponge, and
overcome by reinforcing the bridges, and one
cement; Fibretex which is made out of wood
method of doing this is illustrated in Fig. 9 in
?bre; Transite which is made out ofasbestos and 35 which a, sheet metal strip 92 preferably made of
cement; and Airaco-ustic which is made out of
resilient material, such as spring metal, is em
rock wool and a suitable binder. A number of
bedded in the tile at the bridge during casting of
other companies make sound absorbing tiles or
the tile. If desired, the ends of the spring metal
boards including Armstrong Cork Company, Na
tional Gypsum Company, and United States
Gypsum Company.
In accordance with the present invention, the
may be bent to form spacers or feet 94 on which
40 the reinforce 92 may rest in the mold during the
casting operation. It will be understood that the
section of Fig. 9 is taken longitudinally of the
tile 30 is peripherally cut or slotted as indicated
bridge, or in the same direction as Fig. 8, and
at 32 ‘and 34. In the present case, the slots do
that the metal reinforce 92 is simply an elongated
not go all the way through the board and there 45 rectangular strip disposed longitudinally of the
fore the cuts may be continuous, the connection
between the diaphragm portion 35 and the mar
A simpler method of reinforcming the bridge is
ginal mounting portion 38 being provided by the
that illustrated in Figs. 11 and 12 in which the
uncut thickness indicated at 40.
reinforcing strip 96 is simply cemented to the
In Fig. 3 I show a board or tile in which the 50 bridge 98 on the upper or inner face of the tile.
diaphragm portion 42 is adapted for freer vibra
tion relative to the marginal mounting portion
44. This result is obtained by the use.of through
In the present example the reinforcing strip 96
is a thin strip of wood.
If desired, a thin strip of flexible material, such
cuts 46 and 48 which are not connected end to
as spring metal, may be used as the entire bridge.
end, thus leaving a bridge 50. In the present 55 An example of this is shown in Fig. 10 in which
the diaphragm portion I00 is completely sepa
case, an additional cut 52 is provided parallel
rated from the marginal portion I92 by means
to but spaced from the cut 48, thus elongating
of a continuous peripheral cut IM. They are
the bridge 50 and so increasing its ?exibility.
This, of course, makes the diaphragm portion
again connected together, however, by means of
60 spring metal strips I06 secured thereto by suit
42 more readily vibratile.
able means such as screws. The resulting bridges
In Fig. 4, I show a tile of the thin hard variety,
may be located diagonally at the corners of the
such as metal or plastic, but in this case the bridge
tile, as shown in Fig. 10, and, of course, are pref
52 between the cuts 54 and 56 is elongated by
erably located on the back or inner surface of the
the use of diagonal cuts 58 at each side of bridge
65 tile
52. This obviously increases the ease of vibra
Fig. 13 illustrates one manner in which the
tion of the diaphragm portion 6!].
sound absorbing tiles or boards may be mounted
Fig. 5 illustrates a thick porous tile having
on a wall or ceiling. Furring strips Hi8 are pre—
cuts or slots 62 and 64 which pass nearly but
liminarily fastened to the wall at proper spacing,
not wholly through the thickness of the ma 70
and the tiles are then secured thereto in edge to
terial. A diagonal bridge is provided at each
edge relation by suitable means such as concealed
corner, this being formed by diagonal cuts 66,
nails. It will be understood that the center to
and the bridge may be further weakened for im
center spacing of the furring strips corresponds
proved vibration by a diagonal center cut 68
to the width of the tiles. It will also be under
extending longitudinally of the diagonal bridge 75 stood that the marginal mounting portions of
the tiles. are su?iciently-wide to bring theperiph
gated slots I32. These are in addition, to; pe_—.
ripheral» cuts I34 which free the diaphragm por
eral cuts within or between the furring strips or,
in other words, to localize the diaphragm por
tion to the space between the furring- strips, so
that the diaphragm portion, is freely vibratile.
While in the preceding and succeeding illustra
tions I. show the tiles with. simple square edges, it
will be understood that any of the known inter
locking edges may be employed in order to give
the ?nished wall or ceiling a more ornamental ap
tion for vibration.
The holes for high frequency sound absorption
may pass entirely through the tile, and this, is
illustrated by the holes I36‘ shown, 1121 Fig; 213.
This ?gure, incidentally, illustrates the use, of
diagonal cuts I38 to elongate the bridge I548 be
tween the peripheral cuts IdZ.
In Fig. 22 the holes for high frequency- dissi
pation take the form of- through slots M4,
With through slots, it is, of course, not possible
to use transversely arranged slots» as shown in,
Fig. as. In Fig. 22 the peripheral cuts I461 lead,
15 to a bridge» I48 Which extends parallel to. one»
pearance, and in order to conceal the nails and
to facilitate fastening the tiles in place. Many
such interlocking connections are already known,
and a typical one is that illustrated in Fig. 18, in
which two adjacent edges of; each tile are pro
vidcd with a male edge IIIl, while the other two
edges have a mating female edge “2. These ?t
side of the tile, rather than diagonally thereof.
The bridge is elongated by means of- an extra.
together in a manner clearly shown in the draw
cut I553;
ings, and leave an ornamental V-shaped scoring
Fig. 23 illustrates a porous board having pe-v
I I4, exposed to the eye.
20 ripheral cuts 552 and slots for high frequency
In some cases it may bev more convenient to
sound, these slots being disposed at an angle
secure the sound absorbing tiles directly to a wall
relative to the plane of the tile. There are slots.
as by means of cement, without using any fur-ring
I513 which slope toward the left, as viewed in
strips. For this purpose the marginal mounting.
Fig. 23, and slots I56 which slope toward the
portion of the tile is preferably thickened on the
right. These intersect at a common opening I53‘.
back in order to provide at least a little space to
Fig. 24 is similar, except that the oppositely
accommodate the vibration of the diaphragm
sloping slots ace, I62 are entirely separate from
portion, and to provide a su?iciently large air
space therebehind.
one another.
Fig. 25 shows a thin material such as- sheet
In Fig. 14 an ordinary flat tile is shown thick 30. metal or plastic provided with peripheral cuts
I64, diagonal cuts I 66 forming an elongated
ened at its side edges by the addition of strips
of material H6, these being cemented to the two
bridge I63, and perforations Il-t! to improve the
opposite marginal portions of each tile as a part
e?iciency for high frequencies.
of the manufacture of the tile. The other two
In Fig. 26 there are peripheral cuts I'I;2_ to
edges have been left open, for free air movement.
Fig. 15 illustrates the attachment of these tiles
to awall I I8.
~ divide thetile into a center diaphragm portion
Ill; and a marginal mounting portion I'It‘. In;
stead of perforations the tile portion I'M has
In Fig. 16 I show a more advanced and prefer
slots H3. In the case of a thin material, such
able arrangement in which the thickened mar
as that shown in Figs. 25 and 26, the improve
inal portions I29 are formed integrally with the 40. ment in high frequency dissipation is due to the
remainder of the tile by appropriate shape of the
passage of sound through the perforationsv into
mold used to manufacture the tile. These tiles
the space in back of the tile where the sound is
are shown cemented to a wall or ceiling I722 in
re?ected, dissipated, and absorbed.
Thus the.
Fig. 17. In Figs. 15 and 17 the clearance shown
tile should be spaced from the wall not only to
has been minimized, and in many cases a larger 45 afford vibration of the diaphragm, butfalso to
air space may be wanted,‘ and can. of course, be
improve the dissipation of high frequency sound.
provided. Also ledges may be provided on all
This is illustrated in Fig. 27, in which furring
four edges, if it is- desired to isolate the action of
strips we are preliminarily secured to a wall I82,
each tile. .
following which the thin tilesv I84 are secured to.
As so far described, the tiles are peripherally 50 the furring strips. The titles we may have the
cut and are so mounted as to a?ord vibration of
features of Fig.‘ 25 or Fig. 26, or any desired
most of the area of the tile for purposes of im
combination of these features.
proving the e?iciency of the tile for dampening
Instead of using an unoccupied air space in
low frequency sounds. High frequency sounds
back of the tile, this space may be ?lled by a
may be absorbed or deadened by the porous na
?brous material such as mineral ?bre or rock
ture of the material from which the tile is made.
wool. These materials are now made in the form
If desired, however, the ef?ciency of the tile for
of pads or blankets which may be laid between
absorption of high frequency sounds may be en
the furring strips, as is indicated at I85 in Fig.
hanced by the provision of suitable holes (by
28. In other respects, Fig. 28 corresponds sub
which term I include also slots) out part way or
all the way through the tile.
60 stantially to Fig. 27.
In Fig. 29 I illustrate a modi?ed arrangement
Speci?cally, in Fig. 19 the diaphragm portion,
in which the pads or blankets 0r ?brous mate
I24 is provided with holes I26 which pass part
rial may be held in position by additional fur-1
way through the material. The spacing, diam
ring strips. Speci?cally, a series of parallel furs
eter, and depth of these holes may be selected in
ring strips I38 are preliminarily secured to wall
accordance with known methods heretofore de
I88 in spaced relation. The pads or blankets I32
veloped in connection with-similar boards already
are laid between the furring strips I81; and are
made in a commercial way, but, of course, devoid
held in position by fastening transverse furring
of the peripheral cuts I23 for facilitating vibra
strips I94 to the furring strips I58. The fur;
tion of the center portion acting as, a diaphragm 70 ring strips I88 are properly spaced, to receive
to dampen low frequencies.
the previously made up pads 0r blankets. The
Fig. 20 is a modi?cation in ‘which the holes
furring strips I95 are properly spaced to prop
for improving the eiiiciency of the unit for, high
erly fit the tiles IE6. These tiles may have the
frequency take the form of elongated slots I {It
features of Fig. 25 or Fig. 26, or any desired com
arranged transversely to another series of elon 75 bination of these features.
In some cases it may be desirable to employ
a laminated tile made up of a thin hard surface
material and a thick porous material.
a through one. This helps divide the action of
the tile as a diaphragm, on the one hand, and
For ex
as an absorption medium, on the other.
ample, the sound absorbing property of the thick
comes more complex. Much previously known
data on the absorption of high frequencies may
be employed while using blind holes or slots.
sanitary washable surface as, for example, in
hospitals or the like.
through holes in the diaphragm the theory be
porous material may be wanted together with a
Such a tile is shown in
Fig. 30, it comprising a thin hard material 206
In making the above observation, I do not
cemented to a thick soft porous material 202.
mean that it is undesirable or unsatisfactory to
The combined or laminated board is peripher 10 use through perforations or through slots to aid
ally cut at 204 in order to free the center por
in the absorption of high frequencies. I mean
tion for vibration. The center portion of the
merely that the performance of the diaphragm
thin lamination is perforated as is indicated at
as a diaphragm for the absorption of low fre
206, thus admitting sound to the porous mate
quencies will be affected by an appreciably ex
rial where it tends to be absorbed.
tensive area of through perforation, and the per
Fig. 31 shows a modi?cation in which the
formance data must be appropriately modi?ed.
thick porous backing material 208 is slotted at
While speaking of performance characteristics
2“), these slots being disposed behind and reg
of the tiles, it may be well to point out that the
istering with the holes 2| 2. This improves the
air space in back of the tile affects the natural
ef?ciency with which sound is admitted to the 20 resonance frequency of the diaphragm. Thus,
porous backing material.
if the performance data of a particular tile is
With the tile shown in Figs. 30 and 31 a space
obtained while mounting the tile on furring strips
must be provided in back of the diaphragm to
which are two inches thick, the tile should after
afford vibration of the same. This is readily done
ward be used on similar furring strips which will
when the tiles are to be secured to furring strips.
similarly space the tile two inches from the wall.
If the tiles are to be cemented directly to a wall,
A change to a spacing of only one inch from the
then it is necessary to provide thickened edges
wall will change the performance of the tile.
as was described in connection with Figs. 14
In general, a substantial space is better than a
through 17. However, a modi?ed tile may be
made in which the thin surface material vibrates
while the thick porous material is cemented di
small space where structural considerations make
the use of a substantial space feasible.
rectly to the wall. Such an arrangement is
shown'in Figs. 32, 33, and 34. In this case the
laminated tile comprises a thin hard surface
material which is dished or bent near its pe
are preferably provided having different natural
resonance frequencies. This is desirable in order
to level off the absorption of low frequencies over
the entire low frequency range. For example,
riphery to displace it from the porous backing
material. Speci?cally, the complete tile com
prises a porous back 2| 4 and a metal front 2|6,
there might be ?ve different frequency tiles all
the latter being bent at 2|8 to space the di
aphragm portion from the backing board. The
metal or outer material is peripherally cut as
is indicated at 220, thus freeing the diaphragm
Also a
free movement of air in back of the tiles is thought
desirable by many.
In actual practice a number of different tiles
in the low frequency range.
As a random ex
ample they might respond to or peak at 64, 128,
256, 334, and 512 cycles, respectively.
This different frequency response may be ob
tained by making the bridges wider or narrower
portion for vibration. The parts may be se
cured together by the use of eyelets 222, these
or by making them longer or shorter, or by mak
being convenient because nails and screws for
ing them thicker or thinner. Thus, referring to
securing the laminated tile in position may be
Figs. 35-37, I there show three tiles which are
passed through the eyelets. However, the pres
except that in Fig. 35 the bridge is long;
ent form of tile is ideally suited for cementing
in Fig. 36 it is of medium length; while in Fig. 37,
to Walls because the entire back of the porous
tile may be cemented to the wall. Low fre 50 it is short. In Fig, 35 the bridge is narrow; in
Fig. 36 it is of medium width; and in Fig. 37
quency sound tends to be dampened by vibration
it is wide. Either or both of these changes in
of the diaphragm, while high frequency sound
dimension may be employed with a view to
passes through the perforations and is dissipat
changing the ?exibility of the bridge, and there
ed in the porous material.
by changing the natural resonance frequency of
Fig. 34 illustrates a modi?cation in which the 55 the
backing board 224 is provided with parallel slots
In Figs. 38, 39, and 40 I show sections through
226 to aid in the absorption of high frequency
the bridge (generally similar to the section shown
sound in the porous material. These slots may
in Fig. 8) but in Fig. 38 the bridge is of minimum
register with the lines of holes 228 through the
sheet metal diaphragm, but such registration is 60 thickness; in Fig. 39 it is 0f medium thickness;
and in Fig. 40 it is of increased thickness. The
not essential because of the space between the
bridge of Fig. 38 is more ?exible, and that of
sheet metal surface material and the porous ma
Fig. 40 is less ?exible, than that shown in Fig. 39.‘
In Figs. 41, 42, and 43 I show how the same
An advantage of the laminated forms of the
adjustment may be made with a tile having a
invention shown in Figs. 30 and 31 is that the
“ separate resilient bridge member. In Fig. 41, the
boards are imperforate in respect to low frequen
bridge 233 and the undercut 232 therebeneath
cies, thus obtaining maximum efficiency of vibra
are short; in Fig. 42 the bridge 234 is of medium
tion as a diaphragm. From the viewpoint of
theory and the gathering of performance data,
length and the same applies to the undercut
236 therebeneath, while in Fig. 43 the bridge 238
70 is of maximum length and the same applies to the
phragm, and from this viewpoint the peripheral
undercut 240 therebeneath. Thus the bridge of
cuts which free the diaphragm from the
Fig. 41 will be less yieldable and that of Fig. 43
marginal portion should preferably be thin slits
will be more yieldable than that shown in Fig. 42.
rather than wide slots, that is, there should be
little appreciable width to the out if the cut is 75 In this form of the invention the diaphragm
242 is out free of the marginal portion 244 by
it is a simpli?cation to use an imperforate dia
modate flexing of the spring "strip. The end por
tions of the bridge beyond the undercut are se
large board at the middleyaswellaspat the edges.
It ispossibie to, vary. ih‘ejhr'idses. of thejfollr dia
?hragms, thus 'nr’ovidiiig four ‘different frequency
diaphragm, Onja singleboard. However, for the
curedifto the material ‘of the tile in any suitable
manner, as by cementing the/same in position.
ibility in installing any desired‘ frequency v dia
niean'sfof the penpiierm ‘cut '24s. The undercut
béneaththe bridge provides clearance ‘to accom
sake of simplicity, andv in order to permit of flex
phragrns in any desired proportion for each prob
lem, one may make ‘the fourwdiaphragms inFig.
48 alike,_the large vboard then‘ acting, as ‘a nest
._ Instead of changing the length of the resilient
bridge it may be ‘changed in width (not shown
but analogous to Figs. 35-37) or it may be
of ,four, diaphra'gms all having ‘a common res
changed ‘in thickness. _ This is illustrated in the
drawings in which the bridge of Fig. 41 is thicker
and ‘the bridge ‘of Fig. 43 ‘is thinner than that
shown in Fig. Zl2. It will be understood that any
onance frequency.
designed to_ have a naturalnresonance frequency
in the high part'of the, low frequencyrange, while
the large diaphragm 262 maybe designedto have
20 a natural resonance in the ‘low, partjof thellow
frequency range, Allithese ‘diaphragms may be
provided with holes 216,4jtojaid high frequency
V For a uniform response these may be ar
rangedin staggered relation, one such relation
absorption.” In the ispeci?c case'h'elfehs'hown the
holes. areelongated, blindgslots. arranged in
crossed formation.“ [It will‘ be ‘understood, how
being shown in Fig. 45, in which the tiles marked
1, 2_, 3, 4, and ‘5_ correspond ‘to ?ve different fre- ,
quenc‘ies. It will vbe understood that each of
ever, that round 'holesmay 'bejuseiand that the
holes may‘beulocatedfin the marginal ‘as well ‘as
these tiles is provided with peripheral cuts and
bridges ‘for the diaphragm action, and is pref
erably providedvwith holes for high frequency
absorption. It will be noted thatvtlie ?rst hori
zontal row_ is arrangedv in v's'equ'encefrom 1
diaphragm 262. The small?diaphragm maybe
employed. It will ‘also be understood that while
three ‘different dimensions have been illustrated,
gle board. In this'case thereis a ‘rather small
diaphragm 26.0 located atthe center of a vlarge
natural resonance frequency of the tile ‘may be
ferent frequency tiles.
ing more th'anon'e diaphragm formed on a sin
one or more of these methods of changing the
aj‘g'reater number may be employed, and in prac
tice it may prove ‘desirable to'h'ave, say, ?ve "dif
In Fig. 44 I showa different‘ arrangement hav
the ‘diaphragm, portions of, the ‘complete tile.
Fig, 49furnish
may be.frequenlcytabsorntion
referred. ‘to 835. Showing
the all
over a tile including the "marginal ‘ portion as ‘ well
through 5; that the same applies ‘to, the second
horizontal row, except that it begins with tile
as thediaphra’gm ‘portion. This vniay'fbe fd'one
because‘the operation inre'sp‘ect to'high‘frequen
No. ‘3; while the thirdhorizontal row begins with
tile No. 5; the fourth horizontal row begins with
tile ‘‘No. _2; vthe ?fth horizontal row begins with
tile No. 4;‘vand the sixth horizontal-row repeats
cies doesnot depend upon the diaphragm vibra
tion. wC_)veralluse of ‘holes provides a'm’ore ‘uni
form surface appearance for the wall, which'm'ay
the first horizontal row, that "is, it begins with
be ofadvantage in some instances.
, In most cases the acoustics of a room or hall
may actually be measured before the sound ab
I ._
plete tile istmounted on furring strips 258, ‘so as
to be ‘spacedjfrom the Wall in order vto afford
to the other tiles. Thus in Fig. 46 it is assumed
vibration of the ‘thick ‘absorbent material 263.
that ‘the number of No. 1 tiles is to be doubled.
Each horizontal row is shown arranged with a
No.1 tile between the No; 3 and No. 4 tiles,‘thus
doubling the number of N0. 1 tiles, but dis
This'i's‘peripnerally cut as indicatedfat 210, and
may, bepl‘Qi/i'ded with diagonal cuts and'bridgés,
allkias?previously v‘d'escri'b'eol. , The jinet'al covering
plate ,‘Z?l', ‘however, is ' not provided ‘with periph
tributing the same uniformly. The succeeding
eral cuts andneed not vibrate. ‘It is made very
highly perforate, as ‘isindicat‘e’d by the closely
spaced holesjZTjZ, ‘It is madeso highly perforate
ro'ws'begin with di'iferent tiles as, for example, the
order shown in which the sequence vertically is
the same as that horizontally. Other varrange
the?rnetal kbeingfdished at 1265 and secured to the
tile ‘263, as by means of eyelets 26,6. The'cbm
sorbing treatment is applied thereto. In such
case it may be ‘found, that increased corrective
use of a certain frequency tile is needed relative
ments may, of ‘course, be employed.
Figs. 50,,and51 show anarrangement in which
a thin ‘(for example, metal) surface 'materialIZSl
is combined With‘jathick absorbent materm 2,63,
as to afford ‘adequate free transmission of ‘low
In measuring the acoustics of a room, it may
be found that only one or two different fre
frequencies,_,:,which their ‘cause vibration of the
quency tiles are needed, and it may be found that
one of these is needed more than the other.
Such ‘a situation is illustrated in Fig. 47, in which
thetile is being treated with only the No. 2 and
tion" of jthe‘surface material or ee‘ve'rmg plate ‘26 I.
This, howeveigmayb'e used in‘ order to present an
attractive ‘enamel ?nish where such a ?nish ‘is
No. 3 tiles, and with twice as many No. 3 tiles be
ing used as No. 2 tiles. These may be appro
diaphragm‘263,'there'being nofapfofeciabl'e vibra
desired, \ There 'is'al'so thebe'ne?t'of having two
air spacesfbecau‘seisome high frequency sound
absorptiontakes_‘p1ace ,in ,the 'air ‘space between
priately staggered in any desired relation.
I In. practicing the present invention, it is pos
the laminations 28l ar'id’263.
sible to so cut a large board or tile as to form more
determining the _natural__ resonance frequency of
the t_ilejis_‘the mass of the vibrating diaphragm.
than one diaphragm therein. Such an arrange
ment is shown in Fig. 48 in which the wall has
. e
_ \Itwill be understood that one of the factorsin
This‘depends on its ‘size and, thickness as well as
is so cut as to form four diaphragms 254 which
on the "density of thematerial. Thus in Fig, '44
the’diaphragrn 262 hasfa much larger mass than
the "diaphragm 259, which, in turn, results in a
correspond in size to what would normally be
usedfwith a two foot tile. This facilitates and
speeds up the operation of covering a ceiling or
difference in resonance frequency.
N There: is a con?ict of opinion as to‘wheth'er the
‘air spacelinfbackrjof the vibrating diaphragm
walls, because only a smaller number of boards
must be secured in position.‘ Furring strips may
shouldfor should‘n'ot‘ be sealed. some authori
ties j‘s‘a'y q‘that‘the‘re should preferably be a corn
furring strips 250 and is covered with boards
252 which are, say, four feet square. This board
be used on two foot centers, thus ‘supporting the 75 municat‘ionfr'om one tile to the next. This is ob
tained by using furring strips without any cross
extend part way or all the way through the ma=
terial. The term “bridge” is intended to mean
pieces which might interfere with free flow of air
in the longitudinal spaces between the furring
strips. Similarly, when pieces are cemented to
any connectionwhich holds the diaphragm por
tion to the marginal mounting portion, whether
the back of a tile as in Fig. 14, they are desirably
cemented along only two edges, rather than all
four edges, The same applies when using molded
edges-as in Fig. 16, but in this case it is also pos
sible to simply interrupt the edges to form sev—
eral short well-spaced projections along all four
edges. However, if it is desired to isolate the
effect of each tile, then cross-pieces must be used,
or in the case of Figs. 14 andv 16, the raised edges
should extend entirely around the periphery of
or not elongated. The expression “hole” in con
nection with high frequency absorption is in
tended to include either a through hole or a blind
hole, and either a round hole or elongated hole
such as a slot.
I claim:
1, An acoustic tile comprising a central en
closed vibratile diaphragm section and a mar
ginal diaphragm-enclosing mounting section, the
diaphragm section being inwardly spaced from the
the tile. One treatment may be better for sound 15 mounting section by a peripheral opening there
absorption, say, at the back of an auditorium,
between, the diaphragm section being rigidly con
and the other may be better for sound re?ection,
nected to the mounting section by bridge elements
say, at the stage, but this difference is not critical
bridging said peripheral opening, the diaphragm
to my invention, which is applicable to either the
section thereby forming a vibratile member freely
open or the sealed treatment.
set into vibration at said rigid bridge elements on
It is believed that the method of making and
the mounting section under the impact of sound
using my invention, as well as the advantages
waves, the free vibration of said vibratile member
thereof, will be apparent from the foregoing de
serving to absorb the said sound waves.
tailed description. The improved board or tile
2. An acoustic tile comprising a central en
acts as a diaphragm and vibrates under the im
closed vibratile diaphragm section and a marginal
pact of low frequency sound waves. It dampens
diaphragm-enclosing mounting section, the dia
the waves, the energy being dissipated in the
phragm section being spaced inwardly from the
bridges. The high frequency waves pass into or
mounting section by peripheral diaphragm-de
through the diaphragm and are there deadened
?ning cuts, the diaphragm section being rigidly
or dissipated. The improved tile corrects one of
30 connected to the mounting section by bridge ele
the important defects of previously known tiles,
ments bridging said peripheral cuts, the dia
namely, the fact that they are e?icient over only
phragm section thereby forming a vibratile mem
one end or the other of the audio range. With
ber freely set into vibration at said rigid bridge
my improved tile the best known efficiency for
elements on the mounting section under the im
high frequencies may be retained without loss,
pact of sound waves, the free vibration of said
and eiiicient operation in the low frequency range
vibratile member serving to absorb said sound
is superimposed on that. Relatively free vibra
tion of tiles made of known materials is obtained
3. An acoustic tile comprising a central vi~
in comparatively simple fashion by the use of
bratile diaphragm section and a, marginal dia
peripheral cuts which free the center or dia 40 phragm-enclosing mounting section, both sec
phragm portion from the marginal or mounting
tions being made of the same material, the dia
portion. The resulting spaced bridges may be
phragm section being spaced inwardly from the
made more ?exible by elongating them, or thin
mounting section by peripheral diaphragm-de
ning them, or both, and if necessary the bridges
cuts produced in said material, the dia
may be reinforced to strengthen the same. The
phragm section being rigidly connected to the
tiles may be mounted on furring strips or may
mounting section by bridge elements bridging
be provided with thickened edges and mounted
said peripheral cuts, the diaphragm section there
directly on a wall. Holes may be provided to
by forming a vibratile member freely set into vi
improve the absorption of sound and these may
bration at said rigid bridge elements on the
be round or elongated and may pass part Way
section under the impact of sound
through or entirely through the tile. The space
waves, the free vibration of said vibratile member
. in back of the tile may be left vacant or may be
serving to absorb said sound waves.
?lled with a ?brous material Such as mineral or
rock wool. The tile may be laminated of several
materials, and if desired one of these may be vi
brated relative to the other. In all cases the
edges of the tiles may be appropriately shaped
to form interlocking joints.
Tiles having different natural frequencies may
4. An acoustic tile comprising a central en
closed vibratile diaphragm section and a mar
ginal diaphragm-enclosing mounting section, the
diaphragm section being spaced inwardly from
the mounting section by peripheral diaphragm
deflning cuts, the diaphragm section being rigidly
connected to the mounting section by bridge ele
be provided, and different selections and propor 60 ments bridging said peripheral cuts, the dia
tions of these tiles may be used in accordance
phragm section thereby forming a vibratile mem
with the requirements of any particular installa
ber freely set into vibration at said rigid bridge
tion. Multiple diaphragms may be formed in a
on the mounting section under the im
single tile or board. Holes for high frequency re
pact of sound waves, the free vibration of said
sponse may be formed in the diaphragm or the
65 vibratile member serving to absorb said sound
marginal portion or both.
waves, the said bridge elements being provided
It will therefore be apparent that while I have
with cuts transverse to the peripheral cuts to
shown and described my invention in a number
lengthen and thereby increase the ?exibility of
of preferred forms, many changes and modi?ca
the bridges.
tions may be made in the structures disclosed 70
5. An acoustic tile comprising a central en
without departing from the spirit of the inven
closed vibratile diaphragm section and a marginal
tion, as sought to be de?ned in the following
diaphragm-enclosing mounting section, the dia—
claims. In the claims the term “peripheral cut”
phragm section being spaced inwardly from the
is intended to apply to a cut which frees the dia
mounting section by peripheral diaphragm-de?n
phragm portion for vibration, whether these cuts 75 ing cuts, the diaphragm section being rigidly con
nected to the mounting section by l'bridge "ele
ments bridging said peripheral cuts, 2'the dia
phragm ‘section-thereby ‘forming -'a 'vibratileimem
ber freely set into vibration at ‘said rigid ibridge
eral-outs, the'diaphragm section therebyforming
‘a ‘vibrati-le *member {freely #set ‘into vibration at
‘said rigid bridge ~ elements 1' 0n the mounting sec
tion 'iun'de'rthe impact of sound waves, the free
elements on the mounting section under-the im Or vibration of said rvibratile mem'berrserving to ab
sorb said lsoundwaves, the said bridge-elements
pact of ‘sound Waves of relatively low frequency,
having predetermined dimensions to predeter
the ‘free vibration ‘of saidivibrat'ile member serv
minei-the Vibration period o'f-said diaphragm.
ing to absorb said ‘sound waves, the said, dia
17. :An acoustic‘ tilestructure comprising. in com
phragm being provided with holes in‘or‘der‘to in
10 binationa plurality of acoustic tiles as de?ned
crease the absorption of high frequency‘soun‘d.
6. An acoustic tile "comprising a ‘central -en
closed vibratile diaphrag-msectionand ama-rginal
diaphragm-enclosingmounting section, ‘both-sec
tionsbeing made of *the same material, the'dia
ineclaiin‘l, in which the diaphragm sections are
connected to :the mounting sections solely by
meansiof the bridge elements, and in which the
bridge elements-ofldif‘r‘erenttiles-are of different
phragrn section being spaced inwardly 'from‘the
mounting section by peripheral diaphragméde?n
dimensions ‘in ‘order to ‘vary the natural reso
nance frequency ‘of some of the-diaphragms rela
ing cuts produced in said‘material, the‘diaphragm
section being rigidly connected to the‘mounting
section by bridge elements bridging ‘said periph
tiveito other diaphragms.
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