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BACKGROUND OF THE INVENTION The present invention is housed in a microphone casing
comprising a front acoustic inlet leading to a front volume, a rear acoustic inlet leading to a rear
volume, and a communication volume The present invention relates to a small microphone
having improved windproofness and pop noise prevention, that is, a pressure gradient receiver,
having a microphone capsule.
BACKGROUND OF THE INVENTION Microphone capsules can be configured as pressure
receivers or pressure gradient receivers, regardless of their physical mode of operation. The two
capsule types are distinguished from one another mainly in terms of the achievable directivity
characteristics. The directional characteristics of the microphone capsule are defined as the
sensitivity of the capsule depending on the angle of incidence, and can be represented as
spherical, kidney-shaped, super-renid-shaped, super kidney-shaped, or figure-eight shaped
directivity characteristics with an associated polargraph . A pressure receiver in which the
diaphragm of the capsule is excited on only one side has a spherical directivity.
In order to be able to obtain the directional characteristics of one side, a so-called pressure
gradient receiver has to be made. The pressure gradient receiver not only has an acoustic inlet on
the front side, but may also be embodied laterally or aft, and also has a second acoustic inlet that
allows the diaphragm of the microphone capsule to be exposed to a pressure differential. doing.
The acoustic tuning of the pressure gradient capsule is carried out by means of acoustics known
by the person skilled in the art, whereby both the desired directional characteristics and the
desired frequency profile are obtained.
Although the microphone capsule having a characteristic one-side directional characteristic has a
characteristic to attenuate the interference sound and is in demand, compared to a capsule
having a spherical directional characteristic, against a wind noise and so-called pop noise It also
has major drawbacks. Pop noise is generated when an unfamiliar sound is generated such as "P"
or "B".
Wind noise attenuation is performed by various types of microphone caps in the known prior art.
In this case, the microphone cap, which also serves as mechanical protection for the microphone
capsule, is filled with a wide variety of porous materials. For this purpose, it is mainly a foam with
open cells, which is inserted inside the microphone grid cap or attached to the microphone grid
cap as a windproof cap. The effect of such a windbreaker depends, on the one hand, on the foam
density and, on the other hand, on the distance to the microphone capsule. Higher density foams
generally provide better wind protection, but at higher frequencies also result in loss of
microphone sensitivity. Similar behavior can be seen with regard to the distance from the
microphone capsule to be protected. A large distance means excellent protection, but the
microphone can not be kept small and unobtrusive.
As an example of applying a pop noise preventing device based on a foam material,
EP0130400A2 will be mentioned here. This is a pop noise and wind noise prevention device
made of open-cell foam that is inverted and placed over the microphone casing.
Another method is described in US 4,966,252A. In this case, not only the capsule area of the
microphone, but the entire microphone is incorporated into a windproof casing such as Zeppelin.
DE 298 133 97 U1 likewise describes a form of application of foam which is inverted onto the
microphone casing.
The problem common to all the three examples is that the construction form is complicated and
expensive, and the external weather conditions have a very negative effect on the useful life of
the protective device. It is to be.
A small microphone carried mainly by the human body by belt fixation, pin fixation, adhesion,
placement, etc. is constructed as a pressure receiver for the purpose of reducing the sensitivity of
wind noise and pop noise.
Thereby, although the wind sound sensitivity of the microphone can be suppressed low, on the
other hand, unwanted interference sound is also received from the acoustic environment of the
microphone and transmitted to the next due to the spherical directivity of the microphone.
The application of small microphones with one-sided directivity has hitherto been particularly
difficult due to wind noise sensitivity. Such small microphones are forced to attach an external
protective cap made of foam material.
It is an object of the present invention to provide a small windproof device characterized by
integrating a small-sized microphone consisting of a dynamic capsule or electret capsule having
directional characteristics on one side without complicating the structure of the microphone and
making it expensive. It is to be possible to incorporate into a component of dimensions (for
example a microphone of a headset).
SUMMARY OF THE INVENTION According to the invention, this object is achieved by means of a
narrow passage installed inside the microphone casing when the microphone capsule is in the
assembled state, so that the sound between the front and the back of the microphone capsule is
achieved. This is achieved by establishing a positive connection.
The present invention includes the following aspects.
A miniature microphone comprising a microphone capsule (11) housed in a microphone casing
(12), the microphone casing (12) having a front acoustic inlet (14) leading to a front volume (16);
A rear acoustic inlet (15) communicating with the rear volume (17), the front volume (16) being
connected to the front acoustic inlet of the microphone capsule (11) and The small volume (17)
of the small volume connected to the acoustic inlet on the back side of the microphone capsule
(11), the communication volume (18) between the front side volume (16) and the rear side
volume (17) A small-sized microphone characterized in that
In a first aspect, the communication volume (18) is characterized by a passage.
In the first or second aspect, the front volume (16) and the rear volume (17) are each fully or
partially filled with at least one acoustically transparent foam component (19) It is characterized
4. In the first to third aspects, the communication volume (18) is substantially made up of an
annular gap between the inner surface of the wall of the casing (12) and the outer surface of the
microphone capsule (11) I assume.
5. In the first to fourth aspects, the microphone capsule (11) is characterized by being held by
the nodes or webs (13) of the casing (12).
In the first to fifth aspects, the front volume (16) is characterized in that it has a height having
about one-quarter of the wavelength to be transmitted.
In addition, about the code | symbol, the thing attached to embodiment is referred.
present invention will first be described with reference to FIGS. 1 and 2 below.
FIG. 1 shows the disturbed sound field in which a microphone capsule with two sound inlets a
and b is placed, as shown by the dashed lines.
The pressure situation in the disturbed sound pressure field is shown by a vector diagram in FIG.
Here, the individual vectors have the following meanings. That is, P0 is a static air pressure, and
its intensity change is so slow that it can be ignored. Two vectors Pa and Pb are illustrated at the
tip of the vector P0. The length of vector P0 is longer by a factor of 105 (= 100000) than both of
these vectors. Both these vectors represent the sound pressure situation at the points of both
sound inlets a and b of the microphone capsule shown in FIG. Because the microphone capsule is
compact, the intensity (length) of both vectors Pa and Pb is the same (it is not weakened in such
a short interval). However, the phase positions of these vectors are quite random due to the
disturbance of the sound field.
Two snapshots are depicted in FIG. In the first case (solid line), the vector Pb has a phase angle of
about 45 °, and the vector difference acting as a driving force on the diaphragm of the
microphone capsule has a strength of ΔP1. At another time (dashed line), the vector Pb has a
phase angle of about 120 °. The pressure difference Pa−Pb = ΔP2 at this time is larger than
the individual pressure Pa or Pb.
This means that in a turbulent air pressure environment, which usually occurs when wind noise
and pop noise occur, the diaphragm driving force may be much larger in the pressure gradient
capsule than in the pressure capsule. It means that there is. Moreover, the reason is that, as is
apparent from FIG. 2, the pressure difference between two adjacent points in the turbulent air
pressure field is much higher than the air pressure when the time is taken on the horizontal axis
at the same turbulent air pressure point. It is because there is a possibility of becoming large. A
microphone with such a microphone capsule structure is particularly sensitive to wind noise, and
its attenuation is usually not feasible without very high cost.
FIG. 3 exemplifies a conventional small-sized microphone having one-sided directivity according
to the prior art. A microphone capsule 1 provided with front and rear acoustic inlets (not shown)
is embedded in a hollow cylindrical elastic capsule holding portion 2 that prevents gripping noise
or frictional noise. At this time, the side acoustic port 3 communicating with the rear side volume
7 is incorporated in the microphone casing 4. On the front capsule side, a more or less porous
foam 5 is usually inserted into the front volume with the attached front acoustic inlet 6 in the
microphone casing 4. The role of the foam material 5 is twofold. The first is to thereby guarantee
the dust protection of the capsule and the second is to try to achieve pop noise protection.
However, in this illustrated example, although the microphone capsule 1 implemented as a
pressure gradient receiver has two sound inlets (not shown in particular), in the volume 7 on the
rear side provided with the sound inlet 3 on the rear side. No foam is inserted, and it can be seen
that the capsule holder 2 completely insulates the front volume from the rear volume
(acoustically). In this way, some manufacturing costs are saved, but the wind sensitivity of the
microphone is also increased since the completely identical sound path alone does not lead to
additional pressure differences in the capsule diaphragm.
The lack of foam in the volume 7 on the back side of the microphone increases the pressure
difference in the diaphragm (compared to a complete absence of the foam cover) and thereby
increases the wind sensitivity or pop sensitivity Become.
To that end, in order to provide protection against wind noise or pop noise, an additional
microphone assembly which has a small size (25 mm or less in outer diameter) must be extended
or covered over the entire structure. It is necessary to provide a flexible foam (windproof part).
Disadvantages in this case are the additional space requirements and the degradation of these so-
called additional windproof components due to the action of environmental factors.
Now, an embodiment of the present invention is shown in FIG. 4 and FIG.
A conventional pressure gradient capsule 11 with directional characteristics on one side is
contained in a casing 12 which is usually cylindrical, but can also be constructed in other shapes,
and which project inwardly from the casing wall Web 13 is held.
The casing 12 is provided with an acoustic inlet 14 on the front side and an acoustic inlet 15 on
the rear side.
In the casing 12, the inserted capsule 11 constitutes a front volume 16, a rear volume 17, and a
connection volume 18 connecting the two.
The front volume 16 and the rear volume 17 are each fully or partially filled with at least one
sound-permeable foam component 19.
The connecting volume 18 acts as a calming zone, which, in conjunction with the properties of
the foam part 19, provides a very strong attenuation of wind noise.
The front acoustic inlet 14 allows sound to enter the front volume 16 from the front, so that
sound enters the inlet hole (not shown in particular) on the front of the capsule 11 and also the
connecting volume 18 The sound also enters the rear volume 17 and from there enters the rear
acoustic inlet (not shown in particular) on the rear side of the capsule 11.
The rear wall of the rear volume 17 is acoustically rigidly isolated from the following structure,
which first keeps the volume 17 compact and, secondly, the microphone casing 12 It is internally
sealed and does not allow interference from other volumes.
The connecting line 10 of the microphone capsule 11 is also visible in FIG.
The connecting wire 10 is inserted into the opening, the opening is closed with an adhesive or
other elastic material 21, whereby the remaining volume 20 of the microphone casing 12 may
acoustically interfere with the volume 17 Absent.
The size of each volume and sound inlet is selected to obtain the desired forming of the
frequency response, applying the criteria commonly used in microphone design.
Preferably, the shape and size of the front volume 16 in which the foam 19 is totally filled is
most advantageously its height (the distance between the front of the microphone capsule 11
and the front acoustic inlet 14) , Is chosen to have approximately one-quarter of the smallest
wavelength to be transmitted (the highest frequency to be transmitted). Thereby, by utilizing the
effect as the resonator, when the frequency is high, the transition of the microphone frequency is
The size of the rear volume 17 is primarily so long as the opening 15 is arranged sufficiently
close to the bottom of the capsule 11 and secondly its size allows smooth sound passage It does
not matter. The connecting passage, which is illustrated as connecting volume 18, is preferably
about 0.5 to 2 mm in width (radial length). It is possible to make the connecting path wider than
this, but this makes the microphone more bulky and is only meaningful in exceptional cases.
Furthermore, although the term "volume" in the specification and claims refers to an empty
volume, or a volume partially or totally filled with foam or the like, In either case, it is
acoustically substantially transparent.
The present invention is not limited to the embodiments described above, and various
modifications are possible within the scope of the technical idea described in the claims.
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