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JP2012023753

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JP2012023753
An object of the present invention is to provide a ribbon microphone having excellent
functionality by eliminating damage or distortion to a ribbon caused by external air flow and
wind. A ribbon microphone assembly having adjustable sound reception capabilities. It includes a
transducer 70 having an enclosed flux frame 73 which positions at least two magnets near the
ribbon suspended between the magnets. An array of receiving apertures is provided in the flux
frame. At least one curved return ring 72 is positioned in the receiving aperture to provide a
return path for the magnetic flux in the transducer. [Selected figure] Figure 9
Ribbon type acoustic transducer structure
[0001]
The present invention relates to acoustic transducers, and in particular to ribbon and thin film
transducers and to composite films manufactured in thin film technology and operating at
various audio wavelengths, and to US Provisional Patent Application No. 60/620, 934 and
corresponding US applications, which are incorporated herein in their entirety.
[0002]
Designers and manufacturers of microphones for voice and instrument recording in a studio
environment have sought improvements in methods to achieve precise sound reproduction.
With the general design having low noise, high and low output distortion, high consistency and
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long life, it is preferable to enhance the characteristics of certain types of speech, such as, for
example, a voice, a grand piano, or a woodwind.
[0003]
Microphones typically use transducers and various capacitors. The transducer may be of the
electrodynamic or simply "dynamic" type or ribbon type. Of the three main types of transducers
used in microphones, the present invention focuses on ribbons, but also incorporates certain
improvements and principles that apply to conventional microphones. Transducers, for example
for use in medical delineation, can also be manufactured, used and adapted for use in accordance
with the principles of the present invention.
[0004]
Microphone technology may have progressed faster if it is being assembled and tested using
better materials and fabrication methods, and using techniques compatible with the improved
technology developed by the semiconductor and medical device industries. Device properties,
quality and consistency are improved by precise positioning of moving elements, closed-loop
feedback control of the tuning of the elements, and statistical process control techniques that
reduce part-to-part deviations. By precisely controlling the characteristics of the microphone,
artists and studio technicians can reach and maintain the optimal settings for recording. This
reduces the number of sound checks and retakes required, saving time and production costs.
[0005]
Microphones suitable for use in soundstages and other movie and television production settings
need to be sensitive, robust and reliable, but sensitive to positioning or shaking on boom arms
must not. Such movement causes wind damage and noise to the delicate ribbon suspended in the
magnetic gap. This improvement in the strength and durability of the ribbon structure has made
possible various applications and uses of this type of microphone. In addition, it is desirable to
improve the conductivity of the ribbon and reduce the total mass and strength of the ribbon so
that it is not excessively rigid, ie, output efficiency is improved and toughness is increased. The
output efficiency needs to be high. This is to improve the signal to noise ratio of the microphone
and the overall sensitivity.
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[0006]
The microphone for recording needs to be precise. Each of the microphones assembled in series
should ideally have the same performance. This is not always the case with current microphone
manufacturing. There is a certain variability in the assembly, and tuning of such a microphone
affects the ability to reproduce its sound consistently. There is a need for a precise assembly and
tuning method that overcomes the irregularities that these variations give rise to and results in
accurate component-to-element performance consistency.
[0007]
The external airflow and wind, including the singer's voice or the airflow from the instrument or
amplifier, may be so strong as to damage or distort the delicate internal ribbons used in the
current art. It is desirable to allow normal air flow and sound to circulate freely in the
microphone, and it is also desirable to be able to limit the damaging air blast above a
predetermined intensity level while providing precise sound reproduction without attenuation. .
Such an improvement enables wide use of the ribbon microphone.
[0008]
One object of the present invention is to eliminate the disadvantages of the prior art.
[0009]
A further object of the present invention is to provide a ribbon microphone structure with
excellent functional properties.
[0010]
A further object of the invention is to provide a microphone manufacturing structure that allows
consistent performance characteristics.
[0011]
Accordingly, the present invention includes a ribbon microphone assembly having adjustable
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sound reception capabilities.
The assembly comprises a transducer having an enclosed flux frame for positioning at least two
magnets near a ribbon suspended between the magnets, an array of receiving apertures provided
on the flux frame, and flux of the transducer And at least one curved return ring positioned
within the receiving aperture to create a return path for the motor.
The flux frame may have parallel sides.
The flux frame may have tapered sides. The flux frame preferably has side apertures. The side
aperture may be non-circular. The side apertures may be elongated and curvilinear.
[0012]
The invention also includes a method of making a ribbon for a ribbon microphone. This
comprises providing a first form having an irregular predetermined ribbon engaging surface,
depositing a ribbon forming material on the ribbon engaging surface, and forming a ribbon of the
microphone on the first foam. Includes one or more of the steps. The method comprises the steps
of providing a second foam having a corresponding irregular predetermined ribbon engagement
surface to mesh with an irregular predetermined ribbon engagement surface of the first foam,
and of the first and second foams. Sandwiching the ribbon forming material between ribbon
engaging surfaces. The foam may have its temperature controlled. The ribbon may be of more
than one material. The foam may comprise a deposition aidable material selected from the group
consisting of aluminum, a wax material, and a melting material. The invention also includes a
method of tuning a ribbon for subsequent use of the ribbon in a ribbon microphone. This is the
step of providing a calibration member for adjustably supporting and calibrating the ribbon of
the microphone, wherein the ribbon is formed with a predetermined pattern, and operating the
variable frequency oscillator connected to the loudspeaker The oscillator is set to the desired
resonant frequency of the ribbon, adjusting the calibration member to tension the ribbon, and
observing the maximum displacement of the ribbon exhibiting a resonance peak. Including one
or more. This ribbon is placed in the ribbon microphone transducer assembly.
[0013]
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The invention also includes a method of reducing sound propagation from the microphone
support. This comprises the steps of providing a plurality of ring-shaped spacer members as a
support for a ribbon microphone, inserting an acoustic damping material between adjacent
spacer members, and ribboning the first ends of the plurality of spacer members. And mounting
the second end of the spacer member to a stand of the microphone. The spacer member is
preferably annular.
[0014]
The invention also includes a case for safely enclosing the ribbon microphone, transporting
under pressureless conditions, and in and out. The case includes an enclosure housing, an
openable door on the case, and a spring biased valve connected to the door that opens the case
to an external atmosphere when the door is opened or closed. The casing of the ribbon
microphone enclosing the ribbon therein includes a plurality of sound propagation apertures
passing through the casing enclosing the ribbon. The aperture consists of a curved noncylindrical opening. The aperture is preferably configured to bend away from the ribbon
enclosed in the casing.
[0015]
The invention also includes a modular ribbon microphone assembly. It consists of an upper
ribbon transducer, an intermediate matching transformer section, and a lower amplification and
electronic control section, allowing various combinations of subassemblies to be easily
compatible in the assembly. Each subassembly has a bus bar with interconnect pins that allow
interconnection of the subassemblies.
[0016]
The invention also includes a ribbon transducer that detects energy waves. The ribbon
transducer includes an elongated ribbon structure consisting of conductive carbon nanotube
filaments, the ribbon structure being disposed proximate to the magnetic field and in electrical
communication with the control circuit. The ribbon structure of the carbon nanotube filament
includes ribbon elements of a ribbon microphone. A ribbon microphone having a ribbon element
of carbon fiber material movable therein, the ribbon element comprises an elongated layer of
carbon filaments and an elongated layer of conductive metal attached to the carbon filaments.
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[0017]
The invention also comprises a ribbon transducer for detecting sound waves. The ribbon
transducer is an elongated ribbon structure consisting of conductive carbon nanotube filaments
arranged close to a magnetic field, said ribbon structure being a ribbon structure connected to a
further circuit, and a movable one incorporating carbon nanotube material. It includes a ribbon
element and a ribbon microphone having a movable ribbon element integrated with a carbon
fiber material. The ribbon element comprises a layer of carbon filaments and a layer of
conductive metal attached to the layer of carbon filament material.
[0018]
The invention also includes a composite membrane acoustic transducer structure positioned
proximate to the magnet assembly. The transducer structure and the magnet assembly are
arranged to generate a flux field. The transducer structure includes a first layer of thin, elongated
composite membrane material in which tension is maintained, and a second conductive layer of
membrane material attached to the first layer of composite material. The first and second layers
of membrane material are closely spaced with respect to the magnet assembly, and generally
parallel and offset. This creates a magnetic flux field through at least a portion of the first and
second layers of composite material. The first layer may be made of carbon fiber. The first layer
may be a polymeric material. The carbon fibers may be made of carbon nanotubes. The first layer
is preferably conductive. The second conductive layer is preferably a deposited metal. The
second conductive layer may be an electroplated layer. The second conductive layer may be an
electrodeposition layer.
[0019]
The invention also includes a method of manufacturing a membrane type transducer element.
This comprises the steps of: forming a foam having a predetermined pattern; depositing a metal
layer on the pattern of the foam to create a continuous and separate metal conversion element;
and patterning the deposited metal conversion element And removing the membrane-type
transducer element from the magnetic field. The predetermined pattern may be a periodic
pattern. The predetermined pattern may be a non-periodic pattern. The metal may be aluminum.
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[0020]
The invention also includes a method of manufacturing a ribbon-type acoustic element for a
specific frequency. This is the step of axially mounting the acoustic element in a holder, the
holder having a movable mounting point for supporting the acoustic element, and the step of
moving the mounting point to change the tension of the acoustic element. And one or more of
resonating the acoustic element at a predetermined frequency. The acoustic element may be a
metal element. The acoustic element preferably comprises a transducer assembly.
[0021]
The objects and advantages of the present invention will become more apparent with reference
to the following drawings.
[0022]
Figure 1 is a conventional ribbon microphone transducer showing a corrugated ribbon
suspended between iron poles extending from an electromagnet.
Figure 1 is a conventional ribbon microphone transducer showing a corrugated ribbon
suspended between tapered iron pole pieces extending from a permanent magnet. FIG. 1 is a side
view of a casing of a microphone having a suspension system according to the invention. Figure
4 is a cutaway view of the casing of the microphone shown in Figure 3; It is an expanded
sectional view showing the aperture structure of the casing of the present invention. FIG. 1 is an
exploded cross-sectional side view of a modular ribbon microphone assembly constructed in
accordance with the principles of the present invention. FIG. 7 is a side view showing a stack in
which the converter, transformer, and electronic module shown in the exploded view of FIG. 6
are assembled. FIG. 5 is a side view of a tapered transducer featuring an enclosed flux frame that
positions two or more adjacent magnets near a suspended ribbon mounted therebetween. FIG. 6
is a perspective view of the non-taper (parallel side wall parallel) transducer of the present
invention with a return ring installed. FIG. 9 is a view taken along line 9A-9A of FIG. 9; FIG. 5 is a
side view of the flux frame of the present invention showing features of both tapered and nontaper embodiments. FIG. 2 is a cross-sectional view of an inventive ribbon foam having a
predetermined “ribbon forming” pattern on the foam. FIG. 11b is a cross-sectional view of the
ribbon form shown in FIG. 11a with a deposited metal layer such as aluminum. FIG. 11 b is a side
view of the finished ribbon after removing the metal ribbon from the foam shown in FIG. 11 a.
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FIG. 5 is a cross-sectional view of a finished ribbon created by the deposition process, the ribbon
having a predetermined pattern. FIG. 5 is a side view of a graduated fixture having a scale, a
movable slide, and a plurality of clips holding a ribbon of a microphone therebetween. FIG. 11e is
a schematic view of a tuning system for use with the graduated ribbon holding fixture shown in
FIG. 11e. FIG. 5 is a plan view showing a series of filaments suspended between a pair of filament
holders useful for the manufacture of microphone ribbons. FIG. 12b is a side view of the series of
ribbon filaments shown in FIG. 12a. FIG. 5 is a side view of a series of filaments spaced closely
adjacent between a pair of foams used to apply pressure, heat, or both. Fig. 12c is a side view of a
series of filaments after being embossed by the shape of the foam shown in Fig. 12c. FIG. 7 is a
plan view of a ribbon assembly with a sound absorbing wedge positioned spaced from one side
(in this case the back of the ribbon). FIG. 13b is a detailed side view of the sound absorbing
wedge shown in FIG. 13a. FIG. 6 is a side view, with a cross section, of the microphone assembly
with back lobe suppression.
FIG. 2 is an electrical schematic of a pair of identical ribbons according to the present invention
configured in a parallel circuit configuration. FIG. 7 is a plan view with each ribbon within the
gap of adjacent magnets in a pair of identical ribbons that are close to each other. FIG. 7 is a
perspective view of a practical holder of a pair of adjacent magnets. FIG. 1 is a perspective view
of a storage and travel case for a pressure sensitive device such as a ribbon microphone. Fig. 16b
is a cross sectional view of an air relief valve useful for the travel case shown in Fig. 16a. FIG. 6 is
a side view, with a cross section, of the sound absorbing structure integrated in the microphone
body;
[0023]
Referring in detail to the drawings and in particular to FIG. 1, there is a typical prior art ribbon
microphone transducer 20 of US Pat. No. 1,885,001 by Olson incorporated herein by reference.
It shows a corrugated ribbon 22 suspended between iron poles 24 extending from an
electromagnet 26. The electromagnet 26 establishes a magnetic field that is transmitted near the
voice response ribbon 22 via the pole piece 24. As the ribbon 22 vibrates with incident sound
waves, a current is generated in the ribbon 22 which is amplified, recorded or transmitted. The
typical prior art ribbon microphone transducer 30 shown in FIG. 2 is a tapered iron extending
from a permanent magnet 36, as shown more fully in U.S. Pat. No. 3,435,143 to Fisher, which is
incorporated herein by reference. The corrugated ribbon 32 is shown suspended between the
pole pieces 34 of FIG. The tapered pole pieces 34 reduce the path length between the front and
the rear of the ribbon, thus improving the high frequency response. The ribbon is suspended on
an adjustable frame 38, and screw and nut adjustments are used to precisely tune the position of
the ribbon 32.
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[0024]
However, an improvement of such conventional microphone technology is shown in FIG. Here,
the illustrated microphone casing 40 includes a suspension system 41 consisting of an
elastomeric cord or cable 42 in a zig-zag structure, a tapered body shell structure 44, and a
plurality of sound-transmitting but foreign matter, dust, and other intrusion preventing elements
And an audio screen 46 having an aperture 48. The cutaway view of FIG. 4 shows the
microphone casing 46. The microphone casing 46 has a plurality of spaced apart apertures 48
therethrough, each aperture 48 being axially curved, non-cylindrical, non-linear in shape. FIG. 5
is an enlarged view of the aperture 48, showing how the air blast "W" can be moved away from
near the ribbon "R" under high speed wind conditions. Such redirection of strong flow of fluid is
due to the Coanda effect. This is an effect of changing the flow direction so that the laminar fluid
passing through the curved surface is along the surface. Apertures 48, which are formed with
non-linear contours as shown in FIG. 5, pass normal vibrational waves relatively smoothly, while
potentially destructive airblasts are made of a ribbon "R" or other transducer. Stay away from
such delicate voice pickup devices.
[0025]
FIG. 6 is an exploded view of the modular ribbon microphone assembly 50. The ribbon
microphone assembly 50 comprises an upper ribbon transducer 52, an intermediate matching
transformer section 54, and a lower amplifier and electronic control section 56, allowing a
variety of different ribbon microphone systems to be configured. Direct interconnect pins 58
extending from the bus bars 57 are used to interconnect the sections 52, 54, 56. Microphone
users often want to replace the components of the acoustic chain to adjust gain, frequency
response, timbre, distortion, and other acoustical and electronic attributes. The use of a matched
module setup is used in prior art condenser microphones but not in ribbon microphones. This is
because the ribbon microphone structure prior to the present invention was not consistent in
gain, frequency response, timbre, or distortion. FIG. 7 shows a stack in which the converter 52,
the transformer 54 and the electronic module 56 are assembled. A straight bus bar 57 is used to
connect the motor to the transformer unit and the converter unit to the amplifier / connector
unit. In contrast to the circuit connections of the detours, the connection of straight, preferably in
series fixed positions increases the degree of control of the ham pickup from the external
magnetic field. Wire connections are often routed for the lowest hum pickup because of the
variable nature of the flexible wires. The use of rigid interconnect members 58 virtually avoids
this variability while at the same time ensuring a low resistance and low noise connection. Silver
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bars or silver plated copper provide low resistance and low noise. By using thick conductors and
silver metal, the thermal noise generated in the conductors is also minimized. Generally, in prior
art ribbon microphones, there are three sections that contribute to the overall thermal noise and
other noise floor caused by the completed microphone assembly. These include ribbon sections,
interconnect sections, and transformer sections. It is desirable to use heavy conductors in both
the transformer section and the interconnect section. The ribbon must be made light and
conductive as needed, but improvements to that part are also possible.
[0026]
One preferred embodiment of the transducer 60 is shown in FIG. This is a tapered transducer 60
featuring an enclosed flux frame 61. Enclosure flux frame 61 positions two or more adjacent
magnets close to an elongated, preferably multi-layered suspension ribbon 66 mounted
therebetween. The tapered flux frame 61 shortens the acoustic distance from the front to the
back of the ribbon 66 to improve the high frequency response in the shortened area and is
characteristic of the "parallel" side flux frame Reduce bursts of any high frequency cutoff effects.
The flux frame 61 is provided with a ring receiving aperture 68 near the location of the magnet
62 extending through the flux frame 61. The aperture 68 is positioned to receive a bent return
ring (shown as member 72 in FIGS. 9 and 9A, for example) that is used to create a return path for
the magnetic flux. This increases the strength of the magnetic field in the gap in which the ribbon
66 is disposed, and provides more efficient conversion of sound energy into electrical energy.
This increased efficiency improves the overall output and sensitivity that are desirable attributes
of high quality microphones. The return ring 72 is shaped to have a small cross section for
incident sound waves at any angle. This shape reduces echo and unwanted internal resonances.
While the overall small cross section of the return ring 72 reduces interference and attenuation
of the sound energy but allows the sound energy to reach the ribbon 66 undisturbed, the duty of
magnetic flux propagation is fulfilled.
[0027]
FIGS. 9 and 9a show a non-taper, substantially parallel-walled transducer 70 having a return ring
72 mounting structure. The return ring 72 may be only one or more depending on the length of
the transducer and the amount of magnetic reinforcement / recirculation desired. The return ring
72 may be inserted into the thickness of the flux frame 73 via a press fit to improve the coupling
of the magnetic field thereto. Alternatively, the magnetic flux frame 73 may be attached by
welding.
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[0028]
An embodiment of a further transducer having a flux frame 76 is shown in FIG. The flux frame
76 has features of both tapered and non-taper style, and further includes side apertures 80 to
reduce the front to back distance of the ribbon. This side aperture 80 is known to improve the
high frequency response of the ribbon microphone. The combination of the use of the large
elongated curvilinear / circular side aperture 80 and the use of the tapered assembly allows the
strength of the magnetic field to be maintained.
[0029]
FIG. 11 a is a cross-sectional view of a ribbon form 90 having a predetermined ribbon shaped
surface pattern 92. The foam 90 is made of a wax or meltable material that assists in the
deposition of and plating of metals such as aluminum. FIG. 11 b is a cross-sectional view of a
ribbon form 90 having a deposited layer of aluminum 94. The thickness of this aluminum is
generally about 1/4 micron to about 4 microns. More than one layer (not shown) may be
deposited on surface 92 of foam 90. The layers may be the same material or different materials
having different mechanical and electrical properties. For example, a first layer of gold may be
deposited followed by a thicker second layer of aluminum followed by a third layer of gold or a
combination thereof. The gold layer may be very thin, on the order of hundreds of nanometers.
The layer of aluminum is 500 nm to about 3000 nm and may be more or less depending on the
required size, the desired conductivity, and the total mass allowed for the design.
[0030]
In general, high mass ribbons require a large amount of sound energy to vibrate in the magnet
gap while low mass ribbons may be small. Therefore, it is desirable to minimize the mass.
However, too thin materials, such as, for example, aluminum, have higher resistance as the crosssectional area decreases. The tradeoff between resistance and mass has long been a limiting
factor in the design of ribbon microphones. The tradeoff between strength and mass is similar.
The use of the composites, multilayers and highly conductive materials taught herein increases
design latitude and improves performance.
[0031]
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FIG. 11 c shows by way of example a side view of the finished ribbon 100 after removal from the
foam 90. The preformed metal ribbon 100 is strong, free of cracks or stresses, and not prone to
loosening. Prior art ribbons are formed by bending and / or distorting a flat sheet. Because of
this, there is a compromise in tensile strength, leaving a residual force that causes the ribbon to
loosen over time. FIG. 11 d is a side view of the finished ribbon 102 created by the deposition
process on a foam having a predetermined pattern. This pattern may be periodic, aperiodic, or
graded, with a short wave portion or relief 104 located near the end of the ribbon 102 and a
flatter portion 106 located near the center of the ribbon 102. Be done. Due to the precise and
conformal nature of the deposition process, features such as fine details such as letters (not
shown) or long ribs (not shown) mark portions of the ribbon 102 predetermined flat or surface.
It may be made to be applied or cured.
[0032]
FIG. 11 e shows an example of a graduated fixture 110 having a scale 112, a movable slide 114
and a clip 116 holding a ribbon 118 to be adjusted. 11f is a schematic diagram illustrating a
tuning system 120 for use with the graduated fixture 110 of FIG. 11e. A variable frequency
oscillator 122 is connected to an amplifier 124 which drives the loudspeaker 126 and triggers a
strobe light 128 synchronized with the oscillator 122. The oscillator 122 is set to the desired
resonant frequency of the ribbon 118. The clip 116 is moved until a maximum displacement of
the ribbon 118 is observed which indicates the resonance peak of the ribbon 118 shown in FIG.
The strobe light 128 helps to observe the peak. It also helps to observe any other resonant
modes, including out-of-phase modes that cause distortion. The ribbon 118 is precisely tensioned
using a combination of the device 110 shown in FIG. 11e and the device 120 shown in FIG. 11f
and the procedure followed, and then properly tuned and installed in the transducer assembly.
The ribbon 118 is then connected to a load such as a transformer and a subsequent amplifier, as
needed, during the tuning process. Such fine and precise adjustment of the ribbon 118 improves
the unit-to-unit consistency of the assembly and is highly desirable.
[0033]
FIG. 12 a is a plan view of a series of filaments or fibers 130 suspended between a set of fiber
holders 132. The fibers 130 may be made of a high tensile strength polymeric material such as
non-stretch Kevlar®. The fibers 130 may also be comprised of carbon nanotube fibers, ribbons,
or high tensile strength and low mass composites. For example, such carbon nanotube ribbons
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may be conductive or superconducting. 12b is a side view of the series of filaments 130 shown in
FIG. 12a. FIG. 12c is a side view of a series of filaments proximate to a pair of pattern foams 134
applying pressure, heat, or both. FIG. 12 d is a side view of a series of filaments 130 after being
embossed in the form of foam 134. The series of filaments 130 may be further coated, plated or
covered using a deposition process, such as a deposition process not shown for clarity. The
material to be deposited is aluminum or another conductive material such as gold. Several
materials can be used, including alloys having superconducting properties. Such alloys are
usually rigid and difficult to form into wires, but can be suitably formed in a practical manner by
the disclosed method. The advantage of using such superconductors or very high conductivity
alloys is that a strong, low mass ribbon can be made without lowering the conductivity to the
point where the microphone output falls unacceptably. The superconducting alloy has sufficient
tensile strength to be used alone in this application. Carbon nanotubes or carbon fibers or
ribbons have the advantage of having sufficient conductivity, strength and low mass for use in
this application to improve toughness or resistance to long-term strain, sag or damage is there. At
present, very strong, low mass and high conductivity ribbons are being constructed using such
new technology (such multi-layering is eg bonding, adhesion, deposition, or various interactions
or adhesions) By the process).
[0034]
FIG. 13a shows a top view of a ribbon assembly 140 with a sound absorbing wedge 142 located
at a distance spaced from one side (in this case the back side of the ribbon 143). The sound
absorbing wedge 142 is effective to absorb and attenuate sound energy arriving from the back of
the microphone. A ribbon microphone without a sound absorbing material exhibits a bipolar,
"Fig. 8" acceptance pattern. Sometimes unipolar or unidirectional ribbon movement is required.
Because the back of the ribbon is sealed, sound energy does not reach the ribbon from the back.
The wedges 142 absorb the re-emitted sound caused by the movement of the ribbon. The shape
of the wedge 142 reduces unwanted specular reflection back to the ribbon. Multiple wedges may
be used. The wedge is enclosed to define a chamber 145 having an opening facing the ribbon
143. A detailed view of the sound absorbing wedge 142 is shown in FIG. This heterogeneous
structure consists of filaments, open-cell foam, closed-cell foam 144. Each has an incremental
impedance formed with directivity, and an acoustic impedance for voice that is the same as or
close to the acoustic impedance of air. These increase the loss of heat in the form of heat without
reflection from the whole surface. This configuration absorbs low frequencies at a higher rate
than would be possible with uniform materials such as regular bubbles.
[0035]
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FIG. 14 is a partial cross-sectional view of an example of a microphone assembly 150 with "back
lobe" suppression. An acoustic maze 152 is formed using a rolled or coiled tube 153. The tube
153 is, for example, a plastic tube, Tygon®, or a generally tubular material that can be formed
into other coil types. The formable tubular material can be arbitrarily shaped to fit within the
housing of the microphone 150. The posterior chamber (partially shown in FIG. 13a) may be
connected to the acoustic maze. This may be located at or below the transducer assembly 154 or
around an internal structure or component such as a transformer. The tube 153 is filled with a
lossy voice absorbing material, such as an injected urethane open cell foam, or filled with a lossy
voice absorbing fiber material, such as nylon or aerogel. The length of the tube is typically about
76.2 centimeters (30 inches) as described in the prior art for acoustic maze constructions using
machined ports or chambers. The port or chamber of the prior art is difficult to make and there
is no flexible tube positioning option. One end of the tube is attached to the chamber of FIG. 13 a
to maintain a continuous seal of air across the length of tube 153 from the back of ribbon 143.
Such an arrangement provides a convenient and repetitive configuration of a unidirectional
ribbon microphone system operating as a pressure transducer.
[0036]
FIG. 15a is an electrical schematic of a pair of identical ribbons 160 and 162 fabricated using the
present teachings in a parallel circuit configuration. FIG. 15 b is a plan view of the pair of
identical ribbons 160 and 162 near one another, each within the gap of adjacent magnets 164.
Figure 15c is a perspective view of a practical holder 166 for the pair of adjacent magnets 164
shown in Figure 15b. The holder 166 controls the amount of air or sound that enters the space
between the ribbons (160 and 162) using a sliding aperture stop 167 or other adjustable door
means. By using two identical ribbons (ie 160 and 162), it is possible to create a variable pattern
using ribbon elements in the space of one microphone. Here, excesses due to the identity and
repeatability of the ribbon elements when made using the improved ribbon and microphone
construction methods such as deposition, synchronous tuning, and filament or carbon nanotube
ribbon configurations. There is no distortion.
[0037]
A storage and travel case 170 for a pressure sensitive device, such as a ribbon microphone 172,
is shown in FIG. 16a. Prior art boxes usually have a lid that closes and opens suddenly. Sudden
unprotected action, such as opening and closing the case, may result in unwanted pressure that
can damage the contents. By connecting the air valve 174 to the latch (or hinge), there is a path
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for releasing the air pressure in the opening and closing procedure. FIG. 16 b is a cross-sectional
view of the air relief valve 174. A spring loaded plunger 176 is incorporated into the latch to
release air from the discharge opening 177 before opening. The area of the valve 174 is large
relative to the case 170 and undesirable pressure is not created instantaneously.
[0038]
An example of the microphone support 180 is shown in FIG. FIG. 18 is a cross-sectional view of a
sound absorbing structure integrated within the body of the microphone 182. A plurality of
annular rings 184 are preferably inserted between the acoustically dampening material 186,
such as filled low durometer urethane. This alternating damping material ensures that there is
little noise propagation from the microphone stand 188 into the microphone head. The flat
annular ring construction ensures a reasonably rigid and compact microphone body safely while
ensuring a large area of sound absorption. Although clamp 190 may be rigidly attached to
microphone body base 191, clamp 190 is isolated from the head to reduce or eliminate sound
propagation from the stand to microphone 182.
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