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JPS4948128

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DESCRIPTION JPS4948128
Brief Description of the Drawings. FIG. 1 is a view showing the basic structure of an embodiment
of the secondary sound pressure gradient type 4-channel microphone according to the present
invention, and FIG. 2 is a principle showing a general secondary sound pressure gradient type
directional microphone FIG. FIG. 3 is an equivalent circuit of the microphone shown in FIG. 2, and
FIG. 4 is a polar-faced-table directivity characteristic diagram showing an example of the
directivity characteristic (in the case of ?1 = Q, 5 and ?1 = 1). 5 and 6 show the equivalent
circuit of FIG. 2 respectively ? ? 1 = 0, ? ?! It is a directional frequency characteristic view in
the case of = 1. FIG. 7 is a diagram in principle showing a directional microhots having two
diaphragms, and FIG. 8 is a diagram showing an equivalent circuit of its vibration system. FIG. 9
is a diagram showing in principle another embodiment of the secondary sound pressure gradient
type 4-channel microphone according to the present invention, and FIG. 10 is its pole face
directivity characteristic diagram. L ?, III, IV ииииии Microphone capsule, 1-8 и и и и и и и и и и и и и и и и и и и и и
и и и и и и и и и и и и и и и и и и и и и и и и и diaphragm 12 ииииииии 2 terminal pair acoustic circuit. -69- actual
opening 49-48128 (2)-70 = actual opening 49-48128 (3) Figure 3 Figure 4-7i-actual opening 4948128 (4) Figure 5-6 -Actual opening 49-48128 (5) Fig. 7 Fig. 8 Y-73-Actual opening 49-48128
(6) Fig. 10 = 74-
Detailed Description of the Invention The present invention also relates to a four-channel signal
one-point sound pickup secondary sound pressure gradient microphone comprising four
directional microphones having two diaphragms. -1-Conventional 4-channel stereo sound was
collected using four single directional microphones, which were arranged radially and collected,
but such means require a large number of microphones It is inconvenient for sound collection,
and localization of the sound image is unclear due to phase interference due to the difference in
arrival time of sound waves to the microphones. Further, according to the present invention, a
microphone having four vibrating elements is devised. According to this microphone, a cardioidshaped directivity characteristic in which four directions which are adjacent to each other at an
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angle difference of 90 degrees in the same plane are respectively main axis directions Is
obtained. However, in this case, the directivity is broad, and the case where signals of random
phase are uniformly incident from all directions in the plane is considered. Incident from each
direction of 45 degrees, 135 degrees, 225 degrees, and 315 degrees Sound waves will be
collected additionally, and the sensitivity to dispersed sound differs depending on the direction.
Therefore, when a signal of random phase uniformly enters from any direction, in order to
uniformly pick up sound regardless of the direction, -2 = directivity pattern of one side of the cos
? is required. The object of the present invention is to appropriately configure and arrange such
that the above-mentioned drawbacks can be eliminated, and to uniformly pick up a sound
without depending on the direction when a signal of uniform random phase is incident from all
directions. , Secondary sound pressure gradient j ? 4f consisting of four directional microphones
having two diaphragms. ???? ??????? ???? In the present invention, four
microphones having two diaphragms on the front and back are arranged in a square in the same
plane, and an appropriate phase difference is given to the outputs of the diaphragms on the front
and the back of the opposing microphones to obtain a difference. The diaphragm and the same
two-terminal pair are arranged so that the directivity of each output is in the same plane with an
angle of 90 ░ in the same plane, with four directions adjacent to each other as principal axes. It
is characterized in that the acoustic impedance with the acoustic circuit is appropriately
determined. The present invention will be described in detail with reference to the drawings. FIG.
1 shows the basic structure of a secondary sound pressure gradient type 4-channel 3-channel
microphone according to the present invention using four microphones having two diaphragms
on the front and back. It is a microphone capsule having two diaphragms, 1.2.3.4.5.6.7.8 is a
diaphragm, 9TIi phase shift circuit, El and E2.
E <b> 8 and E <b> 4 are the outputs of the wedge-angle directional microphones whose principal
axes are the X-axis, Y-axis, ?X-axis, and ?Y-axis directions, respectively. In general, in the
secondary sound pressure gradient type directional microphone, primary sound pressure
gradient type microphone capsules are arranged as shown in FIG. 2, and their outputs are phasedifferenced to obtain a difference. Fig. 2 shows an example of a capacitor type: LIIU-next sound
pressure gradient type microphone (capacitor) capsule, 1.2 vi diaphragm, co: capsule
capacitance, R: resistance for phase shift circuit, Rp: bias high A resistor, Cc, is a DC blocking
capacitor, and R11 is a high resistance. When a sound wave is incident on the main axis of this
microphone from a distance in the ? direction, the noise is The sound pressure applied to the
diaphragm of It is given as kkDcos?Po, Po?-4-, respectively. Assuming that the parameter
representing the directivity of each capsule is C1, CC, R is large, so the circuit of FIG. 2 is
represented by an equivalent circuit as shown in FIG. In this figure, Eo is an output voltage when
a sound wave is incident from the direction of the principal axis of each unit. This output voltage
ig is ? Vg1 + jcoCoR, -g no k D cos r ? ?, + cos r ? 7-и (sword E 02 +) oi ', R, l ? i ? 1 where
DCoRo-?,-(2) (The force equation is Vg1 + 7' C11 kD -E) k "" Oa1 + cos r ? EQ 2 + ?, kl) 7 + ?
1 (to become a town, hence hD << 1 in the frequency range satisfying f 1,-, hn (l ▒ ? 1) ?, 10
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cos r ? ci, 10. -No .. (4Lo 21 ▒ (1, 1 + ?. It is expressed as FIG. 4 shows the result of calculation
of the directivity pattern in the case of ?, = 0.5, +, = 1, as an example (from the chrysanthemum
equation. The directivity pattern is almost close to the shape of -5- one of C6S. FIGS. 5 and 6
show the results of calculation of the directional frequency physical properties (in the case where
the capsule is nondirectional and the frequency characteristic is flat) in the case of each ? O1?1-1 from G3). In this figure, when two microphone capsules are combined to make a
secondary sound pressure gradient type microphone, the difference is obtained after tracing the
phase shift circuit rather than the direct difference (?, -O). That is, there is an advantage that the
lower frequency range characteristic is less deteriorated and the high frequency range frequency
characteristic can be made flatterly by setting = 1. Therefore, the combination of ?, = 0.5, ?, -1
is better. The characteristics of the low range in FIGS. 5 and 6 are corrected after amplification.
Next, FIG. 7 shows a directional-microphone having two diaphragms, one character is deleted,
10.11 is a diaphragm, and 12 is a two-terminal pair acoustic circuit.
An equivalent circuit of a vibration system in the case where a sound wave is incident from a
distance in a direction forming ? with respect to the main axis of this microphone is as shown in
FIG. In this figure, the force due to the sound pressure on the diaphragm in front of joB, d is the
effective pressure 111U between the front and back acoustic terminals, the equivalent of u
diaphragm-mechanical impedance, AlBQ, A is a symmetrical two terminal pair acoustic circuit
The terminal constant, ? indicates the velocity of the diaphragm 10, and и indicates the velocity
of the diaphragm 1 ?. ?; + ?; ? in Figure 8 is F. ?: 0 + ? J 8 ? (?)-and (? ? CA + C2,,)) e) k
d cos fls, -7 (5) Fo B-f 2 A2. , G2. . I ask. Here, ? and ? are constants indicating what percentage
of the output voltage of the diaphragm 1.2 is taken out. When the output of the diaphragm 10 is
taken out, the condition of becoming a hypercardioid directivity pattern having zeros in the ??-00 direction is determined as AACZo??jkdco?ao (6). This condition is ([alpha]; 0+ [beta] v1)
kd (([alpha] + [beta]) cos [theta] when substituted into [omega] equation). + (?-?) cos ?) ? (?)
(7) Fo & +-2-9s. From this equation, it is omnidirectional at ?-1 and ?-1, bidirectional at ?-1
and ?-1 and in the positive direction at ?-1?-O. In the case of sex, ?-O?-1, it can be seen that
the hypercardioid directivity, in which the back direction is directed 5-7, is shown. Therefore, if
two directional microphones having two diaphragms as shown in FIG. 7 are used, two wedge
angle directional microphones having the principal axis direction in the front-rear direction can
be changed, as shown in FIG. If four microphones are arranged, four ? -angle uni-directional
patterns can be changed, in which the four directions adjacent to each other at an angle
difference of 90 degrees with each other in the same plane are the main axis directions. In FIG. 9,
I, n, and LIV are directional condenser microphones having two vibrating films as described
above, and 1.2.3.4.5.6.7.8 are vibrating plates. Here, co is a capacitance, a phase shift circuit
resistor, Rp is a bias high resistance, Cc is a DC blocking IL capacitor, and R11 is a high
resistance. pl, j: 2 = 3. j and 4 are the output voltages of the secondary voltage gradient type
directional microphones whose main axes are the X-axis, Y-axis, -X-axis and -Y-axis directions,
respectively. In this structure, ?, = 1 to no. 5, theta. By setting -0-aO, the main axis is oriented in
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the ?-axis, Y-axis, -X-axis and -Y-8-axis direction, and four 2 having directivity patterns as shown
by solid lines in FIG. The next sound pressure gradient type MIKURO can be changed.
The directional butteramine at this time is shown in FIG. 7-F As described above, one microphone
according to the present invention arranges the microphones 4 having two diaphragms in a
square in the same plane, and has an appropriate position for the outputs of the front and back
diaphragms of the opposing microphones. By giving a difference and taking a difference, four
narrow-angle uni-directional patterns can be obtained, each having its main axis in four
directions adjacent to each other at an angle difference of 90 degrees in the same plane. It is
suitable for one-point sound pickup. Furthermore, since the directivity is sharp and the dispersed
sound is not picked up even if the sound source is separated, clear sound quality can be obtained.
Since the ift directivity pattern is almost close to the shape of co?, the dispersed sound from all
directions in the Y plane can be picked up almost uniformly.
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