US4680856

Extracted document text. Layout, formulas and symbols may not survive extraction; consult the preserved PDF for the original presentation.

Text extraction covers 5 pages, including 5 transcribed by optical character recognition.

Page 1

United States Patent 15

Zuccarelli

4,680,856
Jul, 21, 1987

[11] Patent Number:
[45] Date of Patent:

[54] PROCESS FOR FORMING AN ACOUSTIC
MONITORING DEVICE

Hugo Zuccarelli, Corso Roma, 35,
15059 Monleale (AL), Italy

[21] Appl. No.: 816,211
[22] Filed: Jan. 6, 1986

[76] Inventor:

Related U.S. Application Data

[63] Continuation of Ser. No. 591,714, Mar. 21, 1984, aban-
doned, which is a continuation-in-part of Ser. No,
313,027, Oct. 19, 1981, abandoned.

[51] Int. CL#
[52] U.S. CL

HO4R 31/00
29/594; 181/129;
264/222; 264/DIG. 30

[58] Field of Search ............. 29/594, 179/1 G, 1 GA,
179/1 MF, 107, 121 R, 121 D, 147, 153, 156R,

182 R, 182 A; 181/129, 134, 135; 381/25, 26;
264/DIG. 30, 222, 220

[56] References Cited
U.S. PATENT DOCUMENTS
3,985,960 10/1976 Wallace, Jr.
FOREIGN PATENT DOCUMENTS
2437373 2/1976 Fed. Rep. of Germany .

Primary Examiner—Carl E. Hall
Attorney, Agent, or Firm——Stetina and Brunda

179/1G

[57] ABSTRACT

An acoustic monitoring device for sound sensing in the
recording, reproduction, broadcasting, or transmission
of sounds, and a process for forming the device. The
acoustic monitoring device is shaped like a human head
equipped with anatomical features which accurately
reproduce the shape of the auricles, the auditory mea-
tus, the Eustachian tubes, and the nasal and oral cavi-
ties. Membranes responsive to sound pressures are lo-
cated at the positions of the ear drums or other auditory
organs. The device is produced by a process that in-
cludes forming a first mold on a human head, forming a
casting from that mold, forming a second mold on the
casting, and painting the second mold with a liquid
silicone rubber which is allowed to dry to form resilient
casting segments simulating the human head. Anatomi-
cal features simulating the brain and internal members
defining the Eustachian tubes and the nasal and oral
cavities are provided within a skull model. A pair of
membranes is placed within the skull model at the loca-
tion of the eardrums or other auditory organs. These
membranes are coupled to acoustic members which
provide electrical signals on wires exiting the skull
model. The silicon rubber casting segments are trans-
ferred to the exterior of the skull model giving the
acoustic monitoring device the appearance and charac-
teristics of the original human head.

6 Claims, 3 Drawing Figures

Page 2

U.S. Patent

Jul. 21, 1987

FORM A FIRST MOLD OF
A HUMAN HEAD.

FORM A CASTING OF
THE FIRST MOLD.

FORM A SECOND MOLD
OF THE CASTING.

FORM RESILIENT CASTING
SEGMENTS ON THE

SECOND MOLD.

t

4,680,856

PLACE A SIMULATED

BRAIN WITHIN A
SKULL MODEL.

FORM INTERNAL FEATURES
WITHIN THE SKULL MODEL.

PLACE MEMBRANES WITHIN
THE SKULL MODEL.

i

Kg. 3

. COVER SKULL MODEL WITH
THE RESILIENT CASTING SEGMENTS,

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4,680,856

1

PROCESS FOR FORMING AN ACOUSTIC
MONITORING DEVICE

CROSS REFERENCE TO RELATED
APPLICATION

This application is a continuation of U.S. patent appli-
cation Ser. No. 591,714 filed Mar. 21, 1984, now aban-
doned, which is a continuation-in-part of U.S. patent

5

application Ser. No. 313,027, filed Oct. 19, 1981, now 1

abandoned.

BACKGROUND OF THE INVENTION

The present invention concerns an acoustic monitor-
ing device usable in a system for sound sensing, in the
spatial codification or “Holophonic” recording, repro-
duction or broadcasting of sounds, and to a process for
forming such an acoustic monitoring device. More par-
ticularly, the present invention concerns a device, and a
process for forming the device, which device allows
sound sensing in the recording, reproduction or trans-
mission of acoustic perceptions in a manner giving lis-
teners an effective spatial and true, total dimensional
effect, rather than a merely bidimensional one.

Stereophonic recording has been done by placing
two or more microphones in strategic points and re-
cording sounds on a record or tape in two separate
tracks. The sounds recorded on the two separate tracks
are then reproduced through two strategically placed
speakers. In another so-called “binaural” recording
system, an object shaped like a human head is placed
between two panoramic microphones, so as to artifi-
cially create an acoustic shadow to separate the two
recorded stereo channels. Another existing device con-
sists of an artificial head equipped with internal micro-
phones. This device provides only a limited and imper-
fect stereophonic sound recording, and its full effect can
only be appreciated by use of earphones or headphones
because it uses physical delays and physiological delays
created by differences in sound intensity between the
two channels, or a shadowing effect. Still such device
does not provide a Holophonic effect.

The present invention is the result of in-depth re-
search and study and results from another interpretation
of the way in which sound energy interacts with the
human auditory system. Starting from this interpreta-
tion, the present invention provides a system which is
able to give a true perception of the sound received.
The invention can be considered to provide for the
auditory system what laser holography provides for the
visual system and thus can be considered holography of
sound, or “Holophonics.”

An examination of the hearing system shows that it
must analyze information from various sound sources.
In animals in general, the hearing system dynamically
analyzes sound information by the sensorial effect of the
entire body, as well as by spatial codification through
the ears. In man, a highly evolved animal with a highly
perfected hearing system, the hearing system performs
an instantaneous static analysis of sound information,
giving the position of the sound source with respect to
the listener.

This human auditory system includes numerous fea-
tures that contribute to the overall perception of sound
received by a person. These anatomical features include
the ears and their auricles and auditory meatus, the
Eustachian tubes, and the nasal and oral cavities. In
order to provide an acoustic monitoring device permit-

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60

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ting accurate reproduction of auditory sensations, these
anatomical features must be accurately reproduced.
Hair is also of considerable importance in spatial dis-
crimination, allowing a précise perception of sound
coming from the front or the rear by giving rise to an
asymmetric hologram. In fact, bald persons have been
observed to have somewhat reduced front-rear discrim-
ination along the axis of symmetry of the head.

SUMMARY OF THE INVENTION

The present invention is an acoustic monitoring de-
vice and a process for forming such an acoustic moni-
toring device. The acoustic monitoring device is usable
for sound sensing in Holophonic sound recording, re-
production, transmission and broadcasting systems. The
acoustic monitoring device is shaped like a human head,
equipped with anatomical features which accurately
reproduce the shape of the auricles, the auditory mea-
tus, the Eustachian tubes and the oral cavity, as well as
with a wig which serves to generate asymmetry for
front-rear discrimination. Within the acoustic monitor-
ing device, at the end of each auditory meatus, is a
membrane having a cardioid shape, preferably no
smaller than seven millimeters in maximum dimension,
which moves in accordance with the pressures to which
it is subjected, including incoming and outgoing sound
pressures.

The acoustic monitoring device is formed by a pro-
cess that insures that it reproduces as nearly as possible
the characteristics of the human head, particularly the
size and shape of the auricles and the auditory meatus,
but also including the Eustachian tubes, nasal cavities,
and the oral cavity, as well as other components. Thus,
to form the acoustic monitoring device, a first mold is
formed on an actual human head by applying a molding
material such as a dental alginate to the human head.
This mold is preferably formed in segments covering
the full human head, including the auricles, and the
auditory meatus. When the mold has dried sufficiently,
it is removed from the human head in its segments and
assembled to form a full mold of the human head. A
plaster dummy is then made from the first mold. This
plaster dummy, thus, simulates the original human head.
A plaster mold is made of the plaster dummy. After this
second mold has hardened and been removed from the
dummy, the surfaces of the second mold are painted
with a liquid silicone rubber.

The human head from which the first mold was made
is X-rayed or otherwise scanned to determine the size,
shape, and location of its internal features, including its
brain, Eustachian tubes, nasal cavities, and oral cavity.
A simulated brain, of a consistency and resiliency simu-
lating those of the human brain and having a size and
shape substantially equal to the brain size and shape
determined from the X-rays, is placed within a model of
a human skull, preferably a plastic model having acous-
tic properties approximating those of a human skull
such as a medical student might utilize for study. Repre-
sentations of internal members within the human head
are likewise formed of resilient material and are placed
within the skull model, with appropriate size, shape and
position to define cavities simulating features within the
human head, such as the Eustachian tubes, the nasal
cavities, and the oral cavity, as determined from. the
X-rays. A pair of membranes are placed within the skull
model at positions simulating auditory organs of the
human head. Vibrations of the membranes, resulting”

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4,680,856

3

from the various pressures, are transformed to electrical
signals, possibly afer mixing with other pressures such
as reference auditory pressures, and are provided as an
output signal on electrical wires which pass from the
skull model, for example via a passageway communicat-
ing with the oral cavity.

After the silicone rubber has dried on the surfaces of
the second mold, the resulting resilient solid material is
transferred from the second mold to the exterior of the
skull model, giving the acoustic monitoring device the
appearance and characteristics of the original human
head. The resulting acoustic monitoring device permits
realistic sound recording, providing the “Holophonic”
effect discussed above.

Preferably, the acoustic monitoring device is pro-
vided with a wig, a tongue, teeth, and a heating system
which maintains its internal temperature approximately
at that of a human head, about 98.6° F.

In the human head, and thus preferably also in the
acoustic monitoring device of the present invention,
each cavity acting as an auditory meatus is in the shape
of an elliptical cylinder twisted on its axis so that the
wall which is behind the internal orifice inclines gradu-
ally. That is, each auditory canal has a cross-sectional
torsion over the length thereof to cause the longitudinal
extension of a point on the lower surface thereof adja-
cent the auricle to be on the upper surface thereof adja-
cent the eardrum. Further, preferably there is an abrupt
dilation along the length of the auditory canal interme-
diate the ends thereof. In the acoustic monitoring de-
vice each cavity acting as auditory meatus preferably
has an average length along its axis in the range of from
about 24 mm to about 40 mm, simulating the average
length of an actual human auditory meatus. The outer
approximately one-third of the length of the auditory
meatus, adjacent the auricle, is made of the same resil-
ient solid material as the auricle. The inner two-thirds of
the length has a covering layer of more rigid material.
Thus, the surface of the auditory meatus in the device
simulates the outer fibro-cartilaginous portion and the
inner body portion of the auditory meatus of the human
head.

BRIEF DESCRIPTION OF THE DRAWINGS

The process and the device of the present invention
are described below in a presently preferred form, given
only as a non-limiting and ilustrative example, with
reference to the attached drawings in which:

FIG. 1 is a schematic, longitudinal sectional view of
an acoustic monitoring device made in accordance with
the present invention, the view being taken through the
auditory meatus cavities;

FIG. 2 is an enlarged transverse sectional view taken
along line 2—2 of FIG. 1 and showing an aurical and an
auditory meatus of the acoustic monitoring device of
FIG. 1; and

FIG. 3 is a flow chart illustrating a process for form-
ing an acoustic monitoring device in accordance with
the present invention.

DETAILED DESCRIPTION

Acoustic monitoring device 1, depicted in FIGS. 1
and 2, is shaped like a human head and is provided with
two ears 2, each having an auricle 3, which accurately
simulates the auricle of a human ear, and a canal or
cavity 4, which accurately simulates the auditory mea-
tus. A membrane 5 is provided in each ear 2 and can be
placed in the same position and orientation as the ear-

0

40

45

65

4

drum of the ear, as depicted in FIGS. 1 and 2, or can be
placed at the locations of the inner ears or other audi-
tory organs. Each membrane 5 is in free communication
with a tubular cavity 6 which accurately reproduces the
shape of the Eustachian tubes. These cavities-6, in turn,
are in communication with a central cavity 7 which
accurately reproduces the shape of the nasal cavities
and the oral cavity and which, itself, is in communica-
tion with the outside through a tubular cavity 8.

Preferably each auditory meatus cavity 4 has a length
in the range of from about 24 mm to about 40 mm, and
auricles 3 and the outer approximately one-third of each
auditory meatus cavity 4 are preferably made of a resil-
ient material such as a silicone rubber to simulate the
fibro-cartilaginous body material, while the inner two-
thirds of each cavity 4 has an interior layer 11 of plastic,
plaster, or the like, to simulate the bony portions of the
middle ear. The top of acoustic monitoring device 1 is
covered with a wig 9 to provide front to rear asymme-
try to permit front-rear discrimination. Membranes 5
are coupled by appropriate acoustic members to pro-
vide on wires 10 electrical signals representing sensed
pressures, including monitored acoustic pressures.
Wires 10 pass from tubular cavity 6 through central
cavity 7 and exit acoustic monitoring device 1 through
tubular cavity 8.

Many microphones are covered with a porous mate-
rial such as stretched polyurethane to eliminate the
so-called “pop” effect which otherwise would be expe-
rienced. The human ears, and therefore according to
this invention acoustic monitoring device 1, have in
each auditory meatus 4 a sharp dilation 12 which acts
like the muffler of an internal combustion engine for
eliminating this “pop” effect. Therefore, the membranes
5 may be exposed without exhibiting this effect. Each
membrane 5 preferably has a cardioid shape no smaller
than 7 mm in maximum dimension. Each cavity 4, act-
ing as an auditory meatus, has a cross-section of an
elliptical cylinder, with twisting of its axis such that the
longitudinal extension of a point on the lower surface
thereof adjacent the auricle is on the upper surface
thereof adjacent membrane 5.

FIG. 3 is a flow chart illustrating a process for form-
ing an acoustic monitoring device in accordance with
the present invention. A mold of a person’s head is
formed by covering the head with a suitable molding
material. Dental alginate is preferred, since it does not
harm the flesh. The alginate powder is mixed with
water in accordance with the alginate directions, and
the resulting material is applied to the head with suffi-
cient pressure to cause the material to assume the shape
of the head. A hand syringe is used to inject the alginate
material into the ear canal. The head is preferably cov-
ered in segments, and as each segment reaches an appro-
priate dryness, it is removed and stored until all seg-
ments are completed. Such segments might be the face
and neck in one segment, the back of the head in two
segments, and the ears.

The mold segments are then assembled to form a full
head mold. That mold is filled with plaster to form a
plaster casting of the person’s head. Preferably, the
molds of the person’s auricles are not assembled to the
full head mold, since the inclusion of the auricles in the
head casting would make removal of the casting from
the mold difficult. Instead the auricles are cast sepa-
rately and subsequently attached to the head casting.

A second mold is then made of the full head casting.
This second mold is made of a sturdier material than the

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4,680,856

5

first mold. A plaster material is suitable. If necessary,
the plaster head casting can be coated with a release
agent to assure that the plaster mold does not adhere to
the plaster head casting. The second mold is likewise
formed in segments to facilitate its removal from the
head casting. After the second mold segments are dried
and removed from the head casting, the contact surface
of each segment, i.e. the surface of the segment that was
in contact with the head casting, is painted with a liquid
silicone rubber which is then allowed to dry and
harden, forming a set of resilient casting segments of the
human head.

X-rays are taken of the person’s head which was used
to make the first mold. From the X-rays, the size and
shape of the person’s skull and the size, shape, and exact
positioning of internal features of the person’s head are
determined. A plastic skull model is then modified as
necessary to conform to the size and shape of the per-
son’s skull as determined from the X-rays. Such modifi-
cation might include cutting the skull model and adding
plastic material to enlarge it or cutting the skull model
and removing material so as to make it smaller. A suit-
able plastic skull model might be obtained from an edu-
cational supply store, by way of example.

A resilient member of the size and shape of the per-
son’s brain is formed. This simulated brain might be
formed of a polyethylene bag filled with a mixture of
water, alcohol, and cellulose having a density, resil-
iency, and consistency simulating those of the brain.
Alternatively, a silicone rubber material is suitable for
this, since such material has acoustic properties near
those of the human brain. This simulated brain member
is then installed within the skull model in the position
and orientation of the person’s brain as determined from
the X-rays. Likewise, material is used to fashion other
internal features of the person’s head, for example the
cartilage and other material within the head defining
the Eustachian tubes, the nasal cavities and the oral
cavity. These tubes and cavities are fashioned to simu-
late as nearly as possible the corresponding features of
the person’s head as determined from the X-rays. These
features can be formed of an elastomer such as silicone
rubber or a suitable polyester, mixed with suitable cata-
lyzers, hardeners, and/or softeners to provide the de-
sired hardness or resiliency and other characteristics.
The person’s tongue, teeth and neck vertabrae are simi-
larly simulated and attached to the skull model.

Two membranes 5 are installed in the locations of the
ear drums, as illustrated in FIG. 1. Within acoustic
monitoring device 1 various acoustic members are cou-
pled to membranes 5 to complete the Holophonic sound
processing, with the resulting signals passing via wires
10 to suitable recording, reproducing or other process-
ing equipment. Preferably, a thermostat and a heater are
installed to maintain the temperature of the skull model
at approximately the temperature of a human head; i.e.
about 98.6° F. The necessary wiring for the Holophonic
signals and for the temperature control exit the skull
model through the neck for connection to appropriate
circuitry.

Finally, the resilient casting segments of the human

head are removed from the second set of mold segments ,

and are used to cover the skull model, completing the
acoustic monitoring device.

This process, including forming the mold on an actual
human head, has been found to provide an acoustic
monitoring device providing realistic sound recording,
reproduction, transmission and broadcasting, referred

S

5

20

35

40

50

60

to as “Holophonic” sound which has been found to be
a unique sound technique.

Although the present invention has been described
with reference to preferred embodiments, modifications
and rearrangements can be made and the result would
still be within the scope of the invention.

What is claimed is:

1. A process for forming an acoustic monitoring de-
vice shaped like a human head for sound sensing, said
process comprising the steps of:

(a) applying a first molding material to a human head
to form a first mold thereof, such application being
done in segments to provide said first mold in seg-
ments,

(b) removing said first mold segments from the
human head;

(c) assembling said first mold segments to form a full
head mold;

(d) applying a second material to said full head mold
to form a full head casting of the human head;

(e) removing said full head casting from said full head
mold;

(f) applying a further molding material to said full
head casting to form a second mold, such applica-
tion being done in segments to provide said second
mold in segments;

(g) removing said second mold segments from said
head casting;

(h) applying to each of said second mold segments a
liquid material dryable to a resilient solid material;

(i) allowing the liquid material to dry to form a set of
resilient casting segments of the human head;

(j) providing within a human skull model a resilient
member simulating the density, resiliency and con-
sistency of the human brain of the human head;

(k) forming within said human skull model a plurality
of members simulating the cartilage, Eustachian
tubes, nasal cavities and the oral cavity of the
human head;

() placing a pair of pressure-sensitive membranes
within said skull model at positions simulating the
auditory organs of the human head;

(m) coupling said membranes to electrical connec-
tions by means responsive to pressure on said mem-
branes, for generating electrical signals represent-
ing sensed pressures, including monitored acoustic
pressures; and

{n) transferring said set of resilient casting segments
from said second mold segments to the exterior of
said skull model to simulate the exterior of the
human head.

2. A process as claimed in claim 1 in which the first
mold is formed by applying a dental alginate material to
the human head and allowing the dental alginate mate-
rial to dry and harden.

3. A process as claimed in claim 2 in which the apply-
ing of the first molding material to the human head
includes applying the first molding material to the audi-
tory meatus with a hand syringe.

4. A process as claimed in claim 3 in which the cast-
ing of the human head is formed by applying a plaster
material to said head mold.

5. A process as claimed in claim 4 in which the second
mold is formed by applying a plaster material to said
head casting.

6. A process as claimed in claim 5 in which the set of
resilient casting segments is formed by applying a liquid
silicone rubber material to the contact surface of each of
said second mold segments and allowing the liquid sili-

cone rubber material to dry.
+ o* ee