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JPH11331973

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DESCRIPTION JPH11331973
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for
example, a wide-band microphone which extends up to a high frequency band of 100 kHz.
[0002]
2. Description of the Related Art Most microphones of the prior art have a sound pickup
characteristic that can pick up sound in the audio frequency band, since human hearing indicates
that the audio frequency band is up to 20 kHz.
[0003]
As a microphone unit, a dynamic type and a capacitor type are often used as a representative
one.
And, in the conventional microphones for the audio frequency band, the microphone unit is
covered with a microphone cover made of a metal mesh or a metal plate with holes, which
transmits sound, regardless of the type. ing.
[0004]
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The microphone cover protects the microphone unit from physical impact from the outside, and
also plays a role as dust shield, wind protection, and, in the case of a condenser type microphone,
as an electrostatic shield. That is, in the case of the capacitor type, when the electrostatic shield
by the microphone cover disappears, hum is generated. Further, in both the dynamic type and
the capacitor type, wind noise increases if there is no microphone cover. These hum and wind
noise are noise in the audible range. Therefore, in the case of a microphone that picks up audio
in the audible range, the microphone cover is essential.
[0005]
Recently, super audio CDs (compact cassettes) have been proposed that achieve high sound
quality while maintaining compatibility with existing CD players. This Super Audio CD is a
technology called DSD (Direct Stream Digital) that oversamples delta / sigma modulates an
analog audio signal and converts it into a digital signal and directly records the resulting 1-bit
digital audio signal. By using this, it is possible to record wide-band audio information from direct
current to 100 kHz.
[0006]
For this reason, for recording, it is necessary to use a microphone capable of collecting widerange voice from direct current to 100 kHz, but conventionally, a single wide-band microphone
has not been provided.
[0007]
The inventor of the present invention manufactured, as a wide-band microphone as described
above, a microphone unit housed in a microphone cover as a prototype, and measured the
frequency characteristics.
[0008]
Then, it has been found that the presence of the microphone cover prevents the incidence of
ultrasonic waves on the microphone unit, resulting in a reduction in sensitivity to high frequency
sound and disturbance of frequency characteristics in the high frequency range.
[0009]
In view of the above, it is an object of the present invention to provide a wide-band microphone
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capable of improving sound collection characteristics for high frequency sound.
[0010]
SUMMARY OF THE INVENTION In order to solve the above problems, a microphone according to
the invention of claim 1 uses a plurality of microphone units to pick up voice in a wide band
greater than or equal to an audio frequency, and the plurality of microphones A microphone for a
wide frequency band, which is a wide-band microphone for mixing an audio signal from a unit to
obtain an output audio signal, the microphone unit for high frequency sound for picking up high
frequency sound higher than the audio frequency is exposed to the outside. The microphone unit
attached in a state where at least the sound in the audio frequency band is picked up is attached
in a state of being housed in a microphone cover.
[0011]
The microphone according to claim 1 of the above-mentioned configuration is constituted by a
plurality of microphone units.
Then, the high frequency sound microphone unit for picking up high frequency sound higher
than the audio frequency is attached in a state exposed to the outside, and the microphone cover
can not be attached. There is no hindrance to the incidence of sound waves.
For this reason, there is almost no reduction in sensitivity to high frequency sound and there is
little disturbance of the frequency characteristic.
[0012]
Further, since the microphone unit for picking up audio in the audio frequency band is attached
in a state of being housed in the microphone cover, there is no problem of an increase in low
frequency noise such as hum and wind noise.
[0013]
The microphone of the invention of claim 2 is the microphone according to claim 1, wherein the
voice signal from the microphone unit for high frequency sound passes through a filter for
removing a voice signal component of at least an audio frequency band. It mixes with the audio |
voice signal from a microphone unit.
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[0014]
It is possible to solve the problem when the frequency characteristic of the high frequency sound
microphone extends to the low frequency range.
That is, since the high frequency sound microphone does not have a microphone cover, there is a
problem that low frequency noise such as hum sound and wind noise increases. According to the
invention of claim 2, the audio frequency component is increased by the filter. Since it is
eliminated, the problem of the increase in low-pass noise does not occur.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the microphone according to
the present invention will be described below with reference to the drawings.
The microphones according to the embodiments described below are, for example, a low
frequency sound unit that handles a frequency range of 16 kHz or less, for example, a 16 kHz to
40 kHz medium frequency sound unit, and a 40 kHz to 100 kHz high frequency sound
microphone unit, for example. The three-way microphone consists of
In the case of this embodiment, each unit is configured as a condenser type microphone unit.
[0016]
In the case of this embodiment, as will be described later, the low frequency sound unit and the
medium frequency sound unit have an integral coaxial structure to form a single unit in
appearance.
Therefore, in this specification, a unit having an integral coaxial structure of the low frequency
sound unit and the medium frequency sound unit will be referred to as a medium and low
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frequency sound microphone unit.
[0017]
FIG. 1 shows the overall appearance of the microphone of this embodiment, and FIG. 1 (A) is a
front view thereof, and FIG. 1 (B) is a side view thereof.
The medium / low frequency sound microphone unit 1 is attached to the front end side of the
microphone housing 2 formed of a prismatic metal case so that the diaphragm (diaphragm) faces
the front direction. The microphone unit 1 is covered by a microphone cover 3.
[0018]
In the case of this embodiment, the microphone cover 3 plays a role as an electrostatic shield for
a condenser type microphone and plays a role of dust prevention, as shown in a partially
enlarged cross-sectional view of FIG. The mesh 3b is formed of a metal 3a having a hole called
metal and a cloth attached to the inside of the metal 3a. In the case of this example, the aperture
ratio, which is a ratio of the opening 3c of the punching metal 3a to the entire microphone cover
3, is, for example, 50%.
[0019]
As shown in FIG. 1, the high frequency sound microphone unit 4 is attached to the neck portion
of the microphone housing 2 in a state of being exposed to the outside. That is, the high
frequency sound microphone unit 4 is exposed to the outside. However, in this example, in order
to prevent the user or the like from directly touching with a finger, a protective grid 5 configured
by bending a thin metal rod, for example, is provided in front of the high frequency sound
microphone unit 4 There is. The aperture ratio of this protective grid 5 is very large, and the
incidence of high frequency sound on the microphone unit 4 is hardly hindered. The protective
grid 5 may not be provided if there is no risk of touching the user's finger or the like.
[0020]
Inside the microphone housing 2, as described later, there is provided an electric circuit board
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including a preamplifier, a filter and a mixing circuit for mixing high, middle and low three-band
frequency sounds with respect to audio signals from each unit There is.
[0021]
FIG. 3 shows a cross-sectional view of the structure of the low / medium frequency sound
microphone unit 1 used in this embodiment.
As described above, this unit 1 is formed by integrating the low frequency sound unit and the
medium frequency sound unit.
[0022]
In FIG. 3, the unit portion for low frequency sound is mainly composed of a ring-shaped
diaphragm (diaphragm) 11 and a ring-shaped back plate 12 having a predetermined gap
between the diaphragm 11 and the diaphragm. Ru. The ring-shaped diaphragm 11 in this
example has an inner diameter of 18 mm and an outer diameter of 38 mm.
[0023]
Then, a direct current voltage is applied to the capacitor C1 formed of the diaphragm 11 and the
back plate 12 through the high resistance R, and the vibration of the diaphragm 11 caused by
the incident sound wave is formed of the capacitor 11 It is detected as a change in the capacity
of C1 and taken out as a voltage corresponding to the vibration of the sound wave.
[0024]
Further, the unit portion for medium frequency sound is configured in the central opening of the
ring of the unit portion for low frequency sound, and is configured coaxially with the unit portion
for low frequency sound.
The unit for medium frequency sound mainly includes a disk-like diaphragm 13 and a back plate
14 attached with a predetermined gap between the diaphragm 13 and the diaphragm 13. The
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diameter of the diaphragm in this example is 10 mm.
[0025]
Then, a direct current voltage is applied to the capacitor C2 formed of the diaphragm 13 and the
back plate 14 through the high resistance R, and the vibration of the diaphragm 13 caused by
the incident sound wave is generated by the capacitor 13 formed of the diaphragm 13 and the
back plate 14 It is detected as a change in the capacity of C2, and is taken out as a voltage
corresponding to the vibration of the sound wave. The frequency characteristic of the unit
portion for medium frequency sound is extended to 40 kHz.
[0026]
FIG. 4 is a cross-sectional view for explaining the structure of the high frequency sound
microphone unit 4 used in this embodiment. The high frequency sound microphone unit 4 is a
condenser type microphone unit and has a predetermined air gap between the disk-like
diaphragm 41 and the diaphragm 11 via the insulator 43 made of an insulator. And a back plate
42. The diameter of the diaphragm 41 in this example is 4 mm.
[0027]
Then, a direct current voltage is applied to the capacitor C3 formed of the diaphragm 13 and the
back plate 14 through the high resistance R, and the vibration of the diaphragm 41 caused by
the incident sound wave is formed of the capacitor 41 formed of the diaphragm 41 and the back
plate 42. It is detected as a change in the capacity of C3 and taken out as a voltage
corresponding to the vibration of the sound wave. The frequency characteristic of the
microphone unit 4 of FIG. 4 extends to a high frequency range of 100 kHz.
[0028]
FIG. 5 is a block diagram showing the circuit configuration of the electric circuit board in the
microphone housing 2.
[0029]
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That is, a sound wave enters the microphone unit 1 for medium and low frequency sound
through the microphone cover 3 to vibrate the diaphragms 11 and 13.
Further, the sound wave is directly incident on the diaphragm 41 of the high frequency sound
microphone 4.
[0030]
When the diaphragm 11 of the low frequency sound unit portion of the medium and low
frequency sound microphone unit 1 vibrates due to the incident sound wave, the capacity of the
capacitor C1 formed of the diaphragm 11 and the back plate 12 changes, accordingly The charge
/ discharge current flows to the high resistance R, and the audio signal AL is obtained as a
voltage corresponding to the vibration of the low frequency component of the sound wave.
[0031]
The audio signal AL of this low frequency component is impedance-converted through the
preamplifier 51 and then supplied to the mixing circuit 56.
A low pass filter having a pass band of, for example, 16 kHz or less may be provided downstream
of the preamplifier 51.
[0032]
In addition, when the diaphragm 13 of the unit portion for medium frequency sound in the
microphone unit 1 for medium and low frequency sound vibrates due to the incident sound
wave, the capacity of the capacitor C2 formed of the diaphragm 13 and the back plate 14
changes, At the same time, the charge / discharge current flows to the high resistance R, and the
audio signal AM is obtained as a voltage sufficiently corresponding to the vibration of the sound
wave in the frequency band of 16 kHz to 40 kHz.
[0033]
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The audio signal AM is impedance converted through the preamplifier 52 and then supplied to
the high pass filter 53.
In this example, the high pass filter 53 has an intermediate frequency range of 16 kHz or more
as a pass band. The audio signal that has passed through the high pass filter 53 is supplied to the
mixing circuit 56.
[0034]
In addition, the diaphragm 41 of the high frequency sound microphone unit 4 directly vibrates
due to the incident sound wave because there is no microphone cover for this unit 4. For this
reason, high frequency sound waves ranging up to 100 kHz are collected. Then, when the
diaphragm 41 vibrates, the capacity of the capacitor C3 formed of the diaphragm 41 and the
back plate 42 changes, and the charge / discharge current flows to the high resistance R
accordingly, and the vibration of the sound wave of high frequency band up to 100 kHz. The
audio signal AH is obtained as a voltage corresponding sufficiently.
[0035]
The audio signal AH is impedance converted through the preamplifier 54 and then supplied to
the high pass filter 55. The high pass filter 55 has a pass band of 40 kHz or more in this
example. The audio signal that has passed through the high pass filter 55 is supplied to the
mixing circuit 56.
[0036]
The mixing circuit 56 mixes the low frequency range audio signal from the preamplifier 51, the
medium frequency range audio signal from the high pass filter 53, and the high frequency range
audio signal from the high pass filter 55, and outputs the mixed signal as a mixed output. The
sensitivity is high over DC to 100 kHz, and an audio signal output with good frequency
characteristics can be obtained.
[0037]
Next, improvement of the sound collection quality for high frequency sound of the microphone of
this embodiment will be described.
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[0038]
FIG. 6 shows the microphone unit 4 with its frequency characteristic extended to 100 kHz as
shown in FIG. It is an example which measured the sensitivity frequency characteristic.
[0039]
FIG. 7 shows that the same microphone unit 4 is exposed to the outside, that is, the diaphragm
41 is exposed outside, to the neck portion of the microphone housing 2 as in this embodiment as
shown on the left side thereof. This is an example in which the sensitivity frequency
characteristic of the microphone unit 4 is actually measured.
[0040]
Comparing Fig. 6 and Fig. 7, there is no big difference in the sensitivity to the sound of the
frequency of 10kHz-30kHz, but in the frequency range higher than that, the sensitivity decreases
in the case of Fig. 6 at 100kHz. In the case of FIG. 6, the sensitivity is about 10 dB lower than in
the case of FIG.
Further, it can be seen that the frequency characteristic is more disturbed in the case of FIG. 6
than in the case of FIG.
[0041]
As described above, when the high frequency sound microphone unit 4 is housed in the
microphone cover 3 as described above, the presence of the microphone cover prevents the
incidence of ultrasonic waves to the microphone unit, as described above. It is considered that
the desensitization to high frequency sound and the disturbance of the frequency characteristic
in the high frequency range occur.
[0042]
Therefore, as in this embodiment, when the high frequency sound microphone unit 4 is attached
in the state of being exposed to the outside, the disturbance of the sensitivity frequency
characteristic is reduced, and high sensitivity over 100 kHz is achieved. A microphone can be
realized.
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[0043]
In addition, since the high frequency sound microphone unit 4 also has sensitivity in the audio
frequency band, there is no microphone cover, so that the sound component of the audio
frequency band is hum and wind noise due to the absence of electrostatic shielding. Low
frequency noise such as
However, in this embodiment, a high pass filter 55 is inserted into the output signal of the high
frequency sound microphone unit 4 so that the audio component of the audio frequency band is
not supplied to the addition circuit 56. Therefore, the above-mentioned low-pass noise is
eliminated, and the problem of the increase in low-pass noise does not occur.
[0044]
As described above, according to the microphone of this embodiment, the unit 1 for the
collection of medium and low frequency sound and the unit 4 for the collection of high frequency
sound are combined to form a unit for high frequency sound. By attaching 4 to the outside in the
exposed state, it is possible to realize a wide-band microphone having good sensitivity frequency
characteristics up to the ultra-high frequency of 100 kHz.
[0045]
The mounting position of the high frequency sound microphone unit 4 is not limited to the
example shown in FIG.
FIGS. 8 and 9 show another example of the mounting position of the microphone unit 4 for high
frequency sound.
[0046]
That is, in the example of FIG. 8, the unit 4 is attached to the top of the microphone cover 3.
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Further, although the example of FIG. 9 is the outside of the microphone cover 3, it is a case
where the unit 4 is attached so as to be substantially coaxial with the unit 1 for medium and low
frequency sound.
[0047]
In addition, the high frequency sound microphone unit 4 may be attached to any position as long
as it is not in the microphone cover, but as in the example of FIG. 1 of the above embodiment, the
neck of the microphone housing 2 When attached to a part, the distance between the
microphone unit 4 and the preamplifier is shortened because the distance between the
microphone unit 4 and the preamplifier in the housing 2 is shortened, so that the signal
transmission loss is reduced. is there.
[0048]
Needless to say, the microphone unit is not limited to the capacitor type.
[0049]
As described above, the microphone according to the present invention combines a plurality of
microphone units, and the microphone unit for picking up high frequency sound is exposed to
the outside. It is possible to improve the S / N ratio in the very high frequency region without
causing the deterioration of the sensitivity.
In addition, the disturbance of the frequency characteristic in the very high frequency is also
small.
That is, it is possible to realize a wide band microphone having good sensitivity frequency
characteristics up to the very high frequency range.
[0050]
Further, according to the invention of claim 2, since the audio signal component of at least the
audio frequency band from the microphone unit for high frequency sound is removed by the
filter, low frequency noise due to hum sound and wind noise is increased. It is possible to prevent
it from
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