Note: Descriptions are shown in the official language in which they were submitted.
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MODULAR MICROPHONE ARRAY FOR SURROUND SOUND RECORDING
This invention relates to a microphone mounting system which is
primarily but not exclusively designed for use in recording surround
(multichannel)
sound but can be used for monaural (single channel) or stereo (two channel)
sound
recording.
BACKGROUND OF THE INVENTION
In US~atent 5778083 issued 7 July 1998 to Godfrey is disclosed a
surround sound microphone known under the trade mark "Holophone". This was
first marketed in 1999 and company literature states that the Hoiophone
"covers
virtually all forms of microphone technology for recording in surround sound,
including the number of channels or kind of pick-ups for a wide variety of
applications". The Holophone is extremely expensive and complex as a design
for
recording surround sound, the device is not currently being sold. The patent
discloses a microphone system includes a portable frame for mounting linear
pick-up
microphones such that each of the microphones has its diaphragm facing
outwards
from the frame and the diaphragms form a generally elliptical pattern. A
microphone
with a substantially hemispherical pick-up pattern is mounted on the frame
such that
it is directed upwards and a second substantially hemispherical pick-up
pattern
microphone is mounted on the frame directed downwards. The linear pick-up
pattern
microphones are equi-spaced about the perimeter of the frame. There is a hand
or
camera grip depending downwards from the frame. The microphones of the frame
can be electronically connected to the respective channels of a multi-channel
sound
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system, or to the channels of a digital mixer which in turn can be connected
to a
multi-channel sound recording device. The microphones may be selectively
electronically connected to adapt the system for a predetermined sound
playback
configuration.
The patent claims that in all cases the object must be an elliptical, non-
circular pattern or "shape" critical to the microphone placement; the
preferred
embodiment of the mounting frame or object itself is described as
'°generally football-
shaped".
The patent does not describe the shape of the associated ellipse (the
frame) upon which the microphones are mounted as being integral to effecting
the
reception of sound by the object.
Further, the patent specifies that the lateral microphones must be
spaced equidistant from one another, with a control of the pick-up pattern
(number of
channels and I or type of surround recording) switched electronically, remote
from
the device. The patent specifies hypercardiod microphones in fixed placement
around the elliptical shape, with no numerical specification made to the
amount of
microphones.
While the end-user could switch electronically between microphones
much as is specified in the patent, this ability to do so is not specific to
the Modular
Microphone Array design.
In US Patent 4.042,779 (Craven and ~erzon) issued August 1977 is
disclosed a device, based on a set of principles for recording a multi-
channel,
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surround soundfieid in a manner termed B Format. The principles behind the
Soundfield are not directly compatible with the type of recording currently
necessary
for the ITU R 775BS specification for the playback of 5.1 channel surround
sound,
though work is progressing on digits! signal processing (DSP) algorithms that
transform B Format recordings into the ITU R 775BS playback standard.
In professional literature (G. Theile, Das Kugeifiachenmikrofon, 14
Tonnemeistertagung des VDT, Pp 277-293, 1986). Is disclosed the Schoeps Sphere
stereo Microphone KFM 6 which was designed by Dr. Gunther Theile for German
microphone manufacturer Schoeps GmbH. The Stereo Sphere is based on the use
of a 200mm wooden ball-shaped sphere, in which are mounted two opposing
transducers.
A further version of this design, the Schoeps KFM 360, derives
muitichannei surround sound through the addition of two figure-of-eight
transducers,
externally mounted in relation to the existing two opposing transducers. The
developer of this version of the Schoeps Sphere, Jerry Bruck (New York City),
has
stated in print that this design is unpatented and "dedicated to the public
domain" for
further development. This is a design that differs from the arrangement
disclosed
herein in four key areas. First, the shape is fixed as a sphere. Second, in
addition to
the two transducers as found in the original KFM 6 design, that are of fixed
location
within the sphere, the KFM 360 has the two additional figure-of-eight
transducers
placed externally, adjacent to the two internally rr~ounted transducers and
the
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surface of the sphere. Third, the object described depends on signal
processing to
be effective. Fourth, the device is limited to recording only to four
channels.
In US Patent 4658932, April 1987 (Michael Billingsley) and US Patent
4361736 (Ronald Vllickersham and Edward Long) is disclosed a device
manufactured as the Crown PZM and SASS microphone systems which makes use
of the pressure zone effect, which combines the direct sound with the first
reflection
from a nearby boundary to produce a coherent pickup by the microphone
transducer.
In the pressure-zone approach, the linear bandwidth of the transducer
is (in part) dependent upon the spacing of the transducer from the reflecting
surface.
This PZM approach trades off the out-of-band cancellation effects for the in-
band
additive effects that result from summation of direct and reflected sound
reaching the
transducer diaphragm. The mounting configurations for the transducers used in
our
device do not use the pressure zone effect. Instead, the transducers are
mounted in
a coplanar manner that avoids the cancellation effects of nearby surface
reflections
across the entire frequency-range of the transducer.
In European patent EP 0 848 572 A1 (Hitoshi Ishiwata) is disclosed a
microphone unit comprising a semi-spherical structure base, a first microphone
element having at least two directivities which is attached to a left end of
the
structure and a second microphone element having at least two directivities
which is
attached to a right end of the structure. The patent describes a semi
spherical
shape, ranging from 10 to 50 cm in diameter, with four directional microphones
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mounted in pairs, back-to-back on opposing sides of the sphere's surface. This
arrangement results in two microphones facing forwards and two facing
rearwards
on the lateral plane. The resultant sound pick-up provides either a two or
four
channel output, dependant on the routing and processing of the signals
received
5 from the two or four microphones. The patent further describes processing of
the
output signal as integral to providing the desired results of a stereo (2
channel) or
"natural sound" (4 channel) output from the device.
The patent describes a design that differs from the arrangement
disclosed herein in three key areas. First, the shape is fixed as a sphere.
Second,
the transducers are fixed in one location on top of the surface of the sphere.
Third,
the object described depends on signal processing to be effective.
In US Patent 6.041.127 (Elko) issued March 2000 and assigned to
Lucent Technologies is disclosed a first-order differential microphone array
with a
fully steerable and variable response pattern. One illustrative embodiment of
the
present invention comprises a microphone array consisting of 6 small pressure-
sensitive omni-directional microphones flush-mounted on the surface of a 3/"
diameter rigid nylon sphere. The microphones are advantageously located on the
surface at points where included octahedron vertices contact the spherical
surface.
13y selectively combining the three Cartesian orthogonal airs with scalar
weightings,
a general first-order differential microphone beam (or a plurality of beams)
is realized
which can be directed to any angle (or angles) in three-dimensional space. The
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microphone array may find use in surround sound recording /playback
applications
and in virtual reality audio applications.
Calling on an elaborate digital signal processing of the output signals
of its sphere-mounted microphones, the Steerable and Variable First-order
Differential Microphone Array is attempting to create a first-order,
directional
microphone with a steerable signal. The small sphere has six omni-directional
transducers (in the illustrated design) mounted in an orthogonal relationship
on the
surface of the 3/'° diameter sphere, such that with the application of
digital signal
processing to any variety of signal combinations, various directional patterns
of
audio reception can be derived from the output.
The patent claims that the device can be used for surround sound
applications in the abstract of the invention, but this is not elaborated
further in the
body or claims sections of the patent. The output of a surround sound signal
from
this device would most likely exhibit some of the qualities as found in a B
Format
signal (see above, Soundfield I Gerzon) and present DSP challenges in deriving
a
standard ITU R 775BS, 5.1 channel surround sound output, due to the microphone
positions and spacing obtained from the ~/" sphere. This is a design dependant
on
specialized processing to derive a surround output;
US Patent 4.675,906 (Sessler and West) issued June 1987 discloses a
thin-walled, plexiglas cylinder of 5cm outer diameter, hollow with two open
ends
serves as the mounting device for four bi-directional microphones, at 90
degree
intervals on the~wall of the cylinder, as seen from above. The microphones are
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mounted "symmetrically" to the cylinder: flush, with one lobe of the bi-
directional
element of each microphone facing outwards and the second lobe facing inwards.
The open nature of the cylinder thus allows the reception of sound waves
traversing
the cylinder to be received at different intensities; the combination of the
inner and
outer facing lobes of each microphone creates a distinct directional reception
of
sound. Combined, the four microphones have a toroidal pick-up pattern about
the
cylinder, with a distinct bias towards frequency reception in the range of
human
speech. Thus, the device is designed as a single output (monaural) microphone
array for use in applications such as conferencing.
Two further systems have recently been developed in Germany. The
systems are both open framework mounting structures, relying on a suspension
system composed of a central mounting hub and connected metal tubing that
allows
microphones to be suspended in space. The first system has fixed extensions
from
the centre; the second - currently in prototype form - accommodates
adjustment.
The systems are:
The SPL / Brauner Atmos 5.1 which has 'five booms extending from a
centre point, each fixed in distance from that point. Specific Brauner brand
microphones, with pressure gradient transducers facing outvvards from center,
are
mounted on the ends of the booms. The five microphones do not make use of
physical boundaries or structures beyond the typical transducer diaphragm and
housing. This configuration came on the market in 1999 and is still available.
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The Optimized Cardiod Triangle - OCT, which is another design by
Gunther Theile (see Schoeps Sphere), the OCT has adjustable tubing that can
alter,
within small increments of up to approx 20cm, the spacing o~f an array of
individual
microphones. As with the SPL I Brauner device, this design does not make use
of
physical boundaries or structures between all microphones beyond the typical
transducer diaphragms and housings.
SUMMARY OF THE INVENTION
One object is a modular mounting system that accommodates a
variable number and types of transducers (microphones), from a single
microphone
to multiple microphone arrays, intended for use in a variety of audio
recording
methods, ranging from single channel monaural, stereo and as an important
aspect -
surround sound recording.
According to the invention there is provided a microphone mounting
system comprising:
a plurality of mounting elements each arranged to receive and support
a respective microphone transducer;
a plurality of spacer elements;
the mounting elements and the spacer eiements being connectable to
form a body for supporting the microphone transducers in a prearranged array;
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the spacer elements and the mounting elements of the system being
selectable and mountable to provide different arrangements and numbers of the
transducers on the body as required.
The key element is the modular nature of the resulting structure
containing the microphones. ~ capped, circular ring is disclosed in the
description
hereinafter. Several variants on this existing design can also be included;
particularly
but not exclusively one in which the array is made up of sections, much like a
grapefruit, hung on a central post and another in which the outer panels
express an
angular surface, that is a polygon or faceted structure as opposed to a smooth
curve.
Preferably the spacer elements and mounting elements have an outer
surface which can be connected together so that the outer surfaces combine to
define a closed outer surface of the body.
Preferably the closed outer surface of the body is smoothly curved.
Preferably the spacer elements and mounting elements each form a
panel with an outer surface and an inner surface whichi can be connected
together
so that the outer surfaces combine to define a closed outer surface of the
body and
the inner surfaces combine to form a hollow interior of the body.
Preferably the panels have a thickness between the inner and outer
surfaces sufficient to receive the transducer therein.
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Preferably the spacer elements and mounting elements include a set
of elements which combine to form an outer surface which is generally barrel
or
cylinder shaped.
Preferably the spacer elements and mounting elements include a set
5 of elements which provide top and bottom caps on the barrel shape.
Preferably the top and bottom caps are generally dome shaped.
Preferably there are provided different top and bottom caps having
different curvatures which can be selected.
Preferably there is at least one transducer in at least one of the top and
10 bottom cap.
Preferably the mounting elements are acoustically non-resonant, so
that the interior of the body is acoustically damped.
Preferably each transducer is mounted in a resilient, acoustically
dampened sleeve carried in a respective one of the mounting elements.
Preferably each transducer is mounted in the respective mounting
element so that a diaphragm thereof is coplanar with an outer surface of the
mounting element.
Preferably there is provided a mounting post with a support member
carried on the post and surrounding a longitudinal axis of the post with the
mounting
elements and spacer elements carried on the support member at spaced positions
therearound.
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Preferably the support member comprises a disk member having a hub
on the post and a peripheral portion engaging the mounting elements and spacer
elements.
Preferably the disk member includes a pair of axially spaced disks.
Preferably each of the mounting elements and spacer elements
includes a locking projection portion engaging the disk member.
According to a second aspect of the invention there is provided a
microphone mounting system comprising:
a body for supporting a plurality of microphone transducers in a
prearranged array;
wherein the body forms generally a cyiindrical structure having an
outer surface with a generally barrel or cylinder shape with at least some of
the
transducers mounted in the outer surface;
and wherein there are provided top and bottom closure caps to close
the body.
The body may be solid or hollow.
The system is designed through the use of modularity to allow a nearly
infinite variation in microphone spacing through selection of size and type,
and / or
physically positioning the transducers. Sound recordists creating high quality
recordings generally would prefer as direct an unadulterated signal from the
microphone to the recording device as is possible, without the intervention of
signal
processing. The design can accommodate digital signal processing (DSP).
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BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a vertical cross-sectional view through one embodiment of
microphone mounting system according to the present invention.
Figure 2 is a side elevational view of the embodiment of microphone
mounting system of Figure 1 with some of the mounting elements removed.
Figure 3 is a top plan view of the embodiment of microphone mounting
system of Figure 1 with the top cap removed.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In the figures is shown a body 10 for mounting a plurality of
transducers 11 in an array. The body 10 includes a main body portion 11, a top
cap
12 and a bottom cap 13 all mounted on a post 14. The post 14 defines generally
longitudinal axis 15 and the main body portion 11 is generally cylindrical in
shape
surrounding the axis 15 and extending from an upper face 16A to a lower face
16.
The main body portion 11 is formed from a plurality of angularly separated
segments
defining mountings elements 17 and spacer elements 18. Each of these elements
extends around a part of the cylindrical shape defining the main body portion
11 so
that together the segment shaped elements sit side-by-side and form a complete
solid cylindrical body. The body shape has a smoothly curved outside surface
to
form a generally barrel shaped outer surface. The elements also have an inside
surface lying generally on a cylinder surrounding the axis 15. The segment
shaped
elements thus includes side surfaces 17A, 18A which lie in an axial plane and
thus
simply butt side-to-side forming a contiguous outer surface 20 and a
contiguous
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inner surface 21. The outer surface 20 is generally barrel shaped extending
from
the upper edge 16A to the lower edge 16 so that it increases in diameter to a
center
line generally indicated at 22 on which the microphones 100 are located. The
increase in diameter in the embodiment shown is relatively small so that the
radius
of curvature is much greater than that of a sphere centered on the axis 15.
Also the
end caps 12 and 13 are relatively flat. Thus the end caps 12 and 13 have a
domed
outer surface 23, 24 which has a radius of curvature much greater than a
sphere
located on the center line 22. The top cap 12 has an inside surface 25 which
is flat
and similarly the bottom cap 13 has an inside surface 26 which is also flat
with both
lying in a radial plane of the axis 15.
Each of the mounting elements 17 and each of the spacer elements 18
is formed as a solid body from a suitable solid material which may be
plastics, wood
or the like. The upper edge of each of the elements is formed with a notch 28
which
co-operates with a projection 29 surrounding the end cap 12 so as to act to
locate
the elements at there upper edges and prevent outward movement of the elements
relative to the outer surface of the end cap 12.
A bottom surface of each of the elements as indicated at 30 is
substantially flat and fits on top of the top surface 26 of the bottom cap.
The solid body forming the mounting elements 17 is drilled or formed
to provide a boar 30 with an axis lying on the center fine 22 and extending
radialfy
outwardly relative to the axis 15. Within the boar 30 is mounted a sleeve 31
of a
resilient material such as neoprene with an end cap 32 of the sleeve butting
against
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14
the inside surface 21 and the sleeve extending through the thickness of the
element
17 to an outside surface 33 coincident with the outside surface 20 of the
body.
Within the resilient sleeve is mounted the transducer 100 which
provides a generally cylindrical body received as a friction fit within the
inside
surface 34 of the sleeve. An end cap 35 of the microphone stands slightly
proud of
the outside surface of the body. The diaphragm 36 of the transducer is
arranged so
that it lies substantially on the outside surface.
Commercially available transducers are readily available for insertion
into the sleeve. Different size sleeves can be used to accommodate different
sizes
of commercially available transducer.
The transducers are connected via leads 40 to a suitable electrical
connection contained which may be within the hollow interior but in most cases
the
cabling carries through to the outside of the device where connection is
normally
done outside of the device. Some microphone designs leave the connecting
junction
on the body of the microphone, which would hence be internal to, or "within",
the
device.
The post 14 supports the body so that it can be mounted with the post
vertical and the center line 22 thus horizontal. However other orientations
are
possible and the bodies supported on the post so that it can be moved with the
post
as required.
The post 14 carries a mounting disc member generally indicated at 50
which is attached onto a threaded rod 51 carried on the upper end of the post.
The
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disc member 50 includes a lower disc 52 and an upper disc 53. The lower disc
52
surrounds a cap portion 54 of the post 14. The upper disc 53 surrounds the
shaft
51. The shaft 51 is carried on a mounting plate 55 at the top of the post and
is held
in place in that mounting plate 55 by a pair of nuts 56A and 56B threaded onto
a
5 threaded lower section of the shaft 51 and clamping between them the plate
55. An
opening 57 is provided in the bottom cap 13 for exit of the electrical wiring
for
communication of the signals from the transducers.
At the top of the shaft 51 is provided an attachment for the top cap 12,
generally shown at 58. The attachment can be in the form of a simple threaded
10 receptacle which is embedded in the underside of the cap and threads onto
the
upper threaded portion of the shaft 51. However in the embodiment shown, the
attachment 58 comprises a bayonet fitting with a male portion 58A attached to
the
underside of the cap and the female portion 58B attached to the shaft 51 by
nuts
59A and 59B. Thus the top cap can be attached in place simply by inserting the
15 male fitting 58A into the female 58B and rotating through a predetermined
angle to
lock the bayonet fitting in place. This acts to pull the edges of the top cap
down onto
the notch 28 and to hold the structure integral.
A similar bayonet fitting is provided at 60 by which the bottom cap 13
can be slide up over the post and be attached onto the upper end of the post
including the female fitting 60A and the male fitting 60B on the bottom cap.
The discs 52 and 53 act to locate the bottom end of the mounting and
spacer panels. Thus the upper surface of the bottom disc 52 includes a groove
52A
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adjacent its outer edge and this co-operates with a projecting portion 21A of
the rear
surface of each of the panels. The projecting portion has a height
substantially
equal to the spacing between the discs 52 and 53 so that a top surface of the
projecting portion 21A engages the under surface of the disc 53. In addition a
downward projection 21 B on the underside of the projection 21 A engages into
the
recess 52A and provides a shoulder 21 C which engages against the side edge of
the recess 52A. Thus the projection 21A can be snapped into place by slight
distortion of the discs and is held in place by the engagement of the
projecting
portion 21 B and the engagement of the top surface of the projection 21A with
the
underside of the top disc 53.
Thus the structure is integrally and effectively supported upon the disc
member 50 carried on the post. The top and bottom caps can be readily removed
by simply twisting and pulling away from the main barrel shaped body. The
mounting elements and space elements can be snapped out of engagement with the
supporting disc member 50 and rearranged at different angular spacing or
removed
and replaced. Thus the number of transducers can be readily changed by
removing
the mounting elements and replacing them with spacer elements of the same or
different angular dimensions. The spacers can also slide horizontally about
the
radius of the disc member 50, as they are being rearranged.
The above described design facilitates accurate and repeatable
configurations suited to a variety of studio and field recording situations
and
standards. The design supports a wide variety of transducer types
(microphones)
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and is independent of any specific manufacturer's model or type. The novel
overall
shape, with attendant capability to be modified, is a further attribute. The
lightweight,
compact design ensures portability and ease of deployment in recording
situations.
The device described above provides a unique design, one that is
capable of utilisation for a variety of recording situations, ranging from the
reception
of a single, monaural audio output to that of a multi-channel audio - surround
sound -
recording. The device described above facilitates the placement of any number
of
transducers (microphones) in a single mounting device, the amount determined
by
the end-user's recording requirements. The location of each transducer, in
relation to
the overall arrangement of other transducers, becomes determined strictly by
the
needs of the recording engineer I sound recordist.
The modular aspect of this design described above, which is flexible
and variable in nature, is a unique property. Historically, many methods and
designs
for traditional two-channel stereophony have had transducers fixed in
placement,
with little or no flexibility towards the addition or subtraction of
transducer elements.
In such designs for stereo-based arrays, the fixed transducer elements of each
design provided a specific quality to the results. The audio engineer / sound
recordist knew what to expect, including inherent limitations, from each
design.
Contemporary designs for multi-channel, surround sound recording have, to
date,
followed a similar pattern in design, with each existing design suggesting a
single
mode or method of sound reception in the fixed arrangement of the transducers.
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The arrangement described above takes a new approach in
recognition of the variety of context-dependant recording needs and the many
proposed standards for multichannel surround recording. The modular design is
a
first for microphone arrays. By accommodating many potential patterns for the
layout
of the transducer array and the number of channels to be recorded, the
arrangement
disclosed herein allows a degree of flexibility that is not available in other
designs.
The overall shape and size of the arrangement described above has
been designed to allow an acoustically integrated, multi-channel audio
reception of a
soundfield, on a lateral plane for the full 360 degrees around the device.
Further, the
design described above enables the reception of the soundfield above and below
the lateral plane: this can be accomplished through augmenting the lateral
transducer array with the placement of transducers above and below the lateral
plane, that is on the upper or lower sections or domes of the device, if so
required by
the recording session.
An important feature of the cylinder shape of the body is that the ends
of the ring are closed to the exterior so that the resulting interior space is
acoustically
neutralised to avoid internal sound reflection and/or resonance through the
incorporation of acoustical dampening materials. The current design features
the
vertical face of the ring shape canted very slightly inwards top and bottom
from the
centre line.
The device does not need to be manufactured in a modular manner
allowing selection of pieces for different arrangements, but if so, the
modularity of
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the device allows further modification of this face, ranging from completely
flat to
hemispherical, on the vertical axis.
The capped top and bottom of the ring shape can accommodate a
variety of shapes attached to the horizontal plane formed at both ends of the
cylinder. Such shapes range from a completely flat plane to that of a
hemisphere.
Further, the caps seamlessly integrate with the band of the cylinder. However
there
could be an abrupt transition or reflect the current design, which shows a
gentle
curve to the vertical as the caps approach the area of integration with the
top and
bottom of the ring's cylinder. The degree to which the upper and lower caps
vary
from flat to hemispherical is determined by the recording needs. The design
makes
room for variance, due to the modular nature of the upper and lower caps.
The key aspect of modularity in the design is found in the make-up of
the set of modular elements, each capable of presenting either a smooth blank
face
or a smooth face with an integrated transducer; each modular element is nested
in
the device by the disk mounting and accompanied by modules on either side.
Through testing it has been determined that, when placed in the
modules, the diaphragm of the transducer should be presented to the exterior
on the
same plane as the outer face of the device. This is accomplished through the
use of
the sleeve that holds the transducer, fitting directly into a hole in the
mounting
elements. Each transducer is nested in a sleeve of a suitable material, such
as
neoprene, that has been form-fitted for the specific transducer model and
precision
moulded to ensure that the fit is consistent throughout the design. If a
variance
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would be desired from the prescribed transducer placement, which would result
in a
different relationship between the transducer diaphragm and the outer surface
of the
device, the sleeve design could easily accommodate this variance through a
simple
modification of the sleeve design.
5 A further method that would utilise this design is found in the creation
of array patterns through the use of miniature transducers, which are commonly
called lavaliere microphones, where the shape of the device serves as the
foundation upon which to mount the transducers. External yokes can be provided
to
hold the bodies of the transducers in place, the yoke being designed to
position the
10 diaphragm of the transducer in the same plane as the outer surface of the
shape to
avoid acoustical cancellation from surface reflections. This type of
relationship to the
surface of the device is important to maintaining the linear freguency
response of the
microphone. As with the other embodiments of this design, this version can
accommodate a variety of microphone brands. A further advantage of this
15 embodiment of the device is that, as a solid lateral ring, the need for
modular
segments would be eliminated, making this version of the array device less
costly in
manufacture.
The lateral diameter of the current design of this device has been
derived from contemporary research into the "average" human head diameter of
16
20 cm, as measured laterally on the same plane as the ears. The design
principles
behind the shape of the device make the 16 cm diameter an optimal physical
dimension; however, other embodiments of this design may exhibit a variance
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21
smaller or larger than the human lateral diameter. As an example of why there
might
be a variance from the head-related predetermined shape, one needs only
consider
the continuous improvement of digital signal processing, which could enable a
smaller physical device diameter, the signals from which would recreate an
optimal
surround reproduction through the application of high-order digital signal
processing.
With any changes to the lateral diameter of the device, compatible changes in
size
may be made to all other components.
Various aspects of the arrangement as described herein can provide
one or more of the following advantages:
Unique design.
Simple to set up and operate.
Light in weight and compact, robust construction.
Employs a modular concept to facilitate variable placement of
transducers.
Versatility in accommodating many surround recording patterns.
Captures lateral and median plane audio signals.
Thoughtful attention to shape of device ensures high quality,
repeatable results.
The device facilitates the independent selection of transducers that are
currently available and accommodates future transducer designs.
A Main Microphone Surround Array that meets the needs of the audio
profession.
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The arrangement disclosed herein provides audio recording engineers
I location sound recordists with the ability to record a full 360 degree
lateral plane
soundfield with a single device. This is a unique design, modular in nature,
lightweight, compact and one that is simple to set up. The lateral diameter of
the
device is derived from contemporary research that defines the ideal, "average"
human head diameter, as measured laterally at the level of the ears.
When assembled, the device presents a smooth surface with a
prominent shape that provides an optimal reception of sound for surround sound
recording. The spacing of the transducers on a lateral plane, arranged in a
circular
pattern around a central hub, balances the direct and incident sounds from the
sound source. Smoothly modelling the degree of shadowing of each sound source
in
relationship to the sound's location results in strong on-axis reception of
directional
cues for higher frequencies, while positively effecting the off-axis reception
of other
high frequency sources due to the gentle attenuation provided by the smoothly
graduated shape. The design places the plane of the transducer diaphragm in a
planar relation to the surface of the device; this proximity minimizes
cancellation
effects from reflections off the surface surrounding the transducer, creating
a co-
planar relationship between the transducer and the outer surface of the
Modular
Microphone Array.
The wiring for the transducers enters the bottom of the device adjacent
the central mount. Once inside the body of the device, the individual
connecting
cables radiate outwards to each appropriate transducer. The individual
transducer is
CA 02420651 2003-03-03
23
fit into a module via an enveloping sleeve that can be slid directly into the
module,
designed to ensure that the diaphragm of the transducer is on the same level
and
plane as the outer face of the device. In most cases, the protective grill
covering the
transducer's diaphragm stands proud of the outer surFace with this method of
mounting.
The arrangement disclosed herein is welt suited to professional
applications in the set-up portion of the recording process. During set-up
this would
include
1/ ease of initial installation,
2/ predictable and repeatable transducer (microphone) orientation
during preparation for recording,
3I ability to make positional changes of the entire mic array during
recording rehearsals and
4/ ease in disassembly and storage of the array at the conclusion of
the session.
The design facilitates a flexible placement of the transducers in a
lateral, circular pattern, enabling the sound recordist to recreate the
surround
soundfield in a variety of configurations. The device can also serve to
accommodate
a single or several transducers, if monaural or stereo recording techniques
are
desired.
A key quality of an optional arrangement disclosed herein is the ability
to configure the device to a number of professional recording specifications,
for
CA 02420651 2003-03-03
24
music (mono to multi-channel), television / cinema, sound effects, theatre
sound and
audio for computer games. These include the standard 5.1 surround
specification
ITU-R 775BS, Dolby Cinema 6.1, SDDS, Fiolman 10.2, IIVIAX standard and any
equidistant, symmetrical or asymmetrical transducer placement that is suited
for
ambient audio reception in surround. Through this accommodation of many
different
recording standards in multi-channel audio, the embodiment described above
also
represents an elevated level of versatility to the end-user, who will not have
to
purchase separate devices to capture each of the many standards currently
demanded of surround recording. The ability of the device to create
asymmetrical
arrangements of the transducer arrays, rather than simply adhering to
predetermined patterns, is very important in allowing variations to suit field
conditions as determined by the sound recordist.
An additional optional feature of the embodiment described above is
the ability to capture sound signals above and below the lateral plane, if so
desired
by the sound recordist, through transducer placement in the upper and lower
caps.
Future iterations of surround sound playback presentation, including Holman
10.2,
specify overhead playback positions for speaker arrangement in surround audio
presentation. The arrangement disclosed herein is designed to accommodate such
developments.
In operation, the device is light enough to be used on film sets, where it
might be mounted on a hand-held boom pole, the weight factor being critical in
this
application, for on-set pick-up of actor dialogue and interactions, walk-bys I
drive-
CA 02420651 2003-03-03
bys, ambience sound such as crowd noises, forests, street scenes; all of which
could be mixed with on- or off-camera dialogue recordings in post production.
In
music recordings, the compact size and ease of cabling allows the device to be
suspended or flown from ceilings in concert halls or mounted on a single stand
to
5 record musical ensembles. In these and other recording scenarios, the size
and
single mounting point of thE; device ensures that it can be moved and placed
with
ease in the recording environment, until the recording engineer is satisfied
with the
microphone location. Such placement is critical to fidelity, localization,
ratio of direct-
to-reverberant sound balance and immersion in music surround recording
10 techniques, where subtle changes in microphone placement in relation to the
performers and performance space can have a major impact on the quality of
these
outcomes.
The arrangement disclosed herein has been designed to recreate an
acoustic event's soundfield with a high degree of accuracy. This accuracy
includes
15 the ability to locate the point of origin of specific sounds, termed
localization, with a
high degree of resolution and the capability to recreate the overall
soundfield in a
smooth, 360 degree presentation that surrounds the listener, termed
envelopment,
without a noticeable loss of reception in any given direction.
Studies concerning the human reception of a soundfield have
20 determined that the shadowing effect of the human head has no significant
effect at
lower frequencies, where an even distribution of audio wave fronts is critical
for
proper reception of those frequencies. Lower frequencies tend to wrap
themselves
CA 02420651 2003-03-03
26
around objects, with little detrimental effect to the quality of these
frequencies, if
such a transition is gradual. The shadowing effect of the head, however, is
necessary at higher frequencies, where the reception of directional cues that
aid in
the location of sound sources is critical. These factors have been taken into
consideration in the design of the embodiment described above.
Recordings made with the arrangement disclosed herein exhibit a
generous area of envelopment in the playback presentation, commonly referred
to
as the sweet spot in surround sound discussions, negating b~he need to use the
word
spot. Providing such a wide area of envelopment in playback of recordings made
with this device is advantageous to soundtracks in cinema presentations, audio
for
theatrical performances and other presentation applicatioras of surround audio
for
large audiences. In more intimate environments, such as home theatre and
computer gaming, recordings created with the arrangement disclosed herein
result
in a vivid, convincing reproduction of the original soundfield, for listeners
located in
the middle of the soundfield or those offset from the centre.
The optional modular aspect of the design of the embodiment
described above takes advantage of contemporary microphone design, which has
resulted in compact housings for individual, high quality condenser-type
transducers
(microphones). The design supports a wide variety of transducer types and is
independent of any specific manufacturer's model or type. The embodiment
described above has been developed through the use of the compact transducers,
such as the Danish Pro audio 4050 series of transducers. The embodiment
CA 02420651 2003-03-03
2a
described above will be capable of accepting other compact transducer designs,
such as the Schoeps CCM series of condenser microphones. An even larger range
of compact, inexpensive lavaliere-style microphones, made by a host of
international
manufacturers, can also be accommodated by this design.
The embodiment described above is manufactured from suitable
materials known in the art which provide strength and extremely light weight,
acoustical dampening properties, robust wear characiteristics and ease of
machining
and I or moulding in manufacture.
Generally, the embodiment described above consists of a central
space frame or structure that mounts to microphone stands, boom poles and
rigging
hardware. The use of vibration isolation material, commonly known as a shock
mount, may be integrated between the mounting hardware and the central space
frame of the device. Shock mounts are a necessity in providing isolation from
external vibration and movement, which can directly interfere with the
microphone
diaphragm°s ability to pick-up much more subtle sonic vibrations. The
internal space
of the device not occupied by hardware is fitted with nor resonant materials,
to
dampen any internal audio reflections or resonance.
The central frame can be made from a combination of materials: a
lightweight metal alloy and plastic resin. Integrated into this central
structure are the
lower, middle and upper (bottom, ring and top) modules.
The wiring for the transducers enters the bottom of the device adjacent
the central mount. Once inside the body of the device, the individual leads
radiate
CA 02420651 2003-03-03
28
outwards to each appropriate transducer. The transducers are fitted into each
module via an enveloping sleeve, made of a semi-rigid material as neoprene
that
can be placed directly into the module, designed to ensure that the diaphragm
of the
transducer is on the same level and plane as the outer face of the device. In
most
cases, the protective grill covering the transducer's diaphragm stands proud
of the
outer surface with this method of mounting.
The embodiment described above can be used for electronic
conferencing including mufti-channel audio reception and playback, as it could
be
set central to a boardroom table. People at the front, centre or rear of the
room and
on the left or right side of the room would be properly oriented to their
video picture
on the receiving end's surround sound system, providing a concurrent visual
and
aural position of each person.
The device may be large enough to present problems of concealment
in some applications. In this case, the surface of the embodiment described
above
could be of a colour or shade of gray that minimizes visual impact.
The application of digital signal processing could also be used with the
current optimal 15cm size to emulate larger virtual spacings of transducers;
again,
the existing device would be able to simulate this increased radius of
transducer
spacing through DSP treatment of the transducer signal output(s).
The embodiment described above differs from the Holophone prior art
defined above in a number of key areas. First, the transducers in the are
capable of
being arranged in a number of patterns, unlike the faxed pattern described in
the
CA 02420651 2003-03-03
29
Holophone. Second, unlike the Holophone, the output is not dependant upon
signal
processing to provide the desired results of an immersive, surround sound
playback
presentation. Third, the embodiment not only utilizes the outer shape of the
device to
arrange the microphones, but also to tailor the sound reception, an attribute
not
recognized in the Holophone disclosure. Additionally, the coplanar
relationship of the
microphone diaphragms to the surface of the object is not recognized in the
Nolophone disclosure; in fact, the Holophone patent illustrates the diaphragms
of the
hypercardiod capsules placed several centimetres distant from the surface,
essentially rendering this relationship mute.
