JP2017062364

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DESCRIPTION JP2017062364
Abstract: The present invention provides a probe microphone which can be miniaturized without
being affected by a reflected wave of a sound wave from a sound source traveling in a probe
tube. A probe microphone is in communication with a probe tube 1 through which a sound wave
P1 from a sound source S travels, a measurement microphone unit 3 for collecting a sound wave
traveling through a probe tube, and a probe tube A connection tube 2 through which the sound
wave travels, a detection microphone unit 4 for collecting the sound wave traveling in the
connection pipe, and a signal generation unit 5 for generating a cancel signal based on the sound
wave collected by the detection microphone unit. And a speaker 6 for outputting an acoustic
wave P2 for canceling an acoustic wave traveling in the connection pipe based on the
cancellation signal. [Selected figure] Figure 1
プローブマイクロホン
[0001]
The present invention relates to a probe microphone.
[0002]
There is a probe microphone, for example, as a microphone that picks up sound waves in a small
area (sound field) such as measurement of the distribution of sound field inside the device or
sound pick-up of a specific part .
[0003]
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The probe microphone comprises a probe tube and a measurement microphone unit.
The probe tube guides the sound wave from the sound source to the measurement microphone
unit.
The probe tube is elongated and tubular.
[0004]
Sound waves from a sound source enter the probe tube from the tip (front end) of the probe
tube. At the end (rear end) in the probe tube, the acoustic impedance changes. Therefore, the
sound wave (traveling wave) traveling in the probe tube is reflected at the rear end of the probe
tube. The reflected wave reflected at the rear end interferes with the traveling wave. The
interference between the traveling wave and the reflected wave affects the frequency response of
the measuring microphone unit. Also, the interference between the reflected wave and the
traveling wave generates a standing wave having a predetermined resonant frequency. That is,
the sound waves in the probe tube resonate at a predetermined resonance frequency. The
frequency response of such a microphone has a peak at its resonant frequency and is not
constant.
[0005]
As one of the methods of reducing the influence of such a reflected wave, it is proposed to
connect an impedance matching tube to the rear end of the probe tube (see, for example, Patent
Document 1).
[0006]
The impedance matching tube is in communication with the aft end of the probe tube to suppress
changes in acoustic impedance at the aft end within the probe tube.
The impedance matching tube is elongated and tubular. The length in the longitudinal direction
of the impedance matching tube is set sufficiently longer than the length in the longitudinal
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direction of the probe tube in accordance with the frequency band of the sound wave collected
by the measurement microphone unit.
[0007]
Here, the longitudinal direction of the probe tube is a direction connecting one end (front end)
and the other end (rear end) of the probe tube when the probe tube is formed into a straight
tubular shape. Further, the longitudinal direction of the impedance matching tube is a direction
connecting one end (front end) and the other end (rear end) of the impedance matching tube
when the impedance matching tube is a straight tube.
[0008]
The cross-sectional area of the impedance matching tube in a cross-sectional view in the
direction orthogonal to the longitudinal direction of the impedance matching tube is substantially
the same as the cross-sectional area of the probe tube in a cross-sectional view in the direction
orthogonal to the longitudinal direction of the probe tube. The impedance matching tube is
housed, for example, in a serpentine shape in a case of the probe microphone.
[0009]
The measurement microphone unit has a flat frequency response in a predetermined frequency
band. The measurement microphone unit is disposed at a connection portion (hereinafter
referred to as connection portion ) between the probe tube and the impedance matching
tube.
[0010]
In the probe microphone thus configured, the impedance matching tube is in communication
with the probe tube and also plays a role of extending a substantial length in the longitudinal
direction of the probe tube. That is, the substantial longitudinal length of the probe tube is the
longitudinal length of the probe tube plus the longitudinal length of the impedance matching
tube. As a result, the resonance frequency of the probe tube deviates from the frequency band of
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the sound wave collected by the measurement microphone unit. Further, since the cross-sectional
area of the probe tube and the cross-sectional area of the impedance matching tube are
substantially the same, the acoustic impedances in the probe tube and the impedance matching
tube do not change at the connection portion. As a result, sound waves traveling through the
probe tube do not reflect at the back end of the probe tube. Therefore, the conventional probe
microphone is configured to be less susceptible to the influence of the reflected wave in the
frequency band of the sound wave collected by the measurement microphone unit disposed at
the connection portion.
[0011]
Japanese Utility Model Application Publication No. 5-060083
[0012]
However, the impedance matching tube needs a sufficient length for the wavelength of the sound
wave collected by the measurement microphone unit.
That is, the length of the impedance matching tube can not be shortened because it depends on
the wavelength of the sound wave collected by the measurement microphone unit. In addition, a
probe microphone provided with a long impedance matching tube must secure a space for
housing the impedance matching tube. Therefore, miniaturization of the probe microphone
provided with the impedance matching tube has been difficult.
[0013]
The present invention has been made to solve the problems of the prior art as described above,
and is a probe microphone which can be miniaturized without being affected by the reflected
wave of the sound wave from the sound source traveling in the probe tube. The purpose is to
provide
[0014]
The present invention relates to a probe tube through which a sound wave from a sound source
travels, a measurement microphone unit for collecting sound waves traveling through the probe
tube, a connecting pipe in communication with the probe tube and a sound wave from the probe
tube to travel Based on the detection microphone unit that picks up the sound wave traveling in
the pipe, the signal generation unit that generates a cancellation signal based on the sound wave
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picked up by the detection microphone unit, and the sound wave traveling on the connecting
pipe based on the cancellation signal And a speaker for outputting the sound wave into the
connection tube.
[0015]
According to the present invention, it is possible to provide a probe microphone which can be
miniaturized without being affected by the reflected wave of the sound wave from the sound
source traveling in the probe tube.
[0016]
It is a schematic diagram which shows embodiment of the probe microphone concerning this
invention.
It is a schematic diagram which shows another embodiment of the probe microphone concerning
this invention.
[0017]
Hereinafter, embodiments of a probe microphone according to the present invention will be
described with reference to the drawings.
[0018]
Configuration of Probe Microphone FIG. 1 is a schematic view showing an embodiment of a
probe microphone according to the present invention.
The probe microphone M1 is referred to as a probe tube 1, a connection tube 2 and a
measurement microphone unit (hereinafter referred to as "measurement unit").
3) and a detection microphone unit (hereinafter referred to as "detection unit").
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4), the signal generator 5, the speaker 6, and the case 7). The probe tube 1 and the measurement
unit 3 are sound waves from the sound source S (hereinafter referred to as sound waves P1 ).
The measurement unit that picks up The connection tube 2, the detection unit 4, the signal
generation unit 5, and the speaker 6 constitute a cancellation unit that cancels the sound wave P
1 from the probe tube 1. As described later, the probe tube 1 and the junction tube 2 are in the
form of an elongated tube.
[0019]
In the following description, among the two ends of the probe tube 1 of the probe microphone
M1, one end side (left side in the drawing) where the sound wave P1 from the sound source S
enters the probe tube 1 at the time of sound collection is called the front end of the probe tube 1
The end side (right side in the drawing) is referred to as the rear end of the probe tube 1.
Further, among the both ends of the connection pipe 2, one end side (left side in the drawing)
through which the sound wave P1 enters the connection pipe 2 from the probe pipe 1 at the time
of sound collection is referred to as the front end of the connection pipe 2, It is called the rear
end of the connection pipe 2.
[0020]
The probe tube 1 guides the sound wave P1 from the sound source S to the unit 3 for
measurement.
[0021]
The material of the probe tube 1 is, for example, one having flexibility such as a synthetic resin.
The probe tube 1 is an elongated tubular shape. The probe tube 1 has a circular inner space of
an inner diameter d1 in a cross-sectional view in the direction orthogonal to the longitudinal
direction of the probe tube 1. The longitudinal length L1 of the probe tube 1 affects the
frequency response characteristic of the measuring unit 3. Therefore, the length L1 in the
longitudinal direction of the probe tube 1 is set according to the frequency band of the sound
wave P1 collected by the measuring unit 3.
[0022]
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Here, the longitudinal direction of the probe tube 1 is a direction connecting the front end and
the rear end of the probe tube 1 when the probe tube 1 is formed into a straight tubular shape.
[0023]
The material of the probe tube 1 may be a hard material such as metal.
Also, the probe tube 1 may be made of a plurality of materials. That is, for example, the front end
side of the probe tube 1 may be made of metal, and the remaining portion may be made of
synthetic resin.
[0024]
The internal space at the front end of the probe tube 1 is filled with an acoustic resistance
material 10 made of a sponge or the like. That is, the front end of the probe tube 1 is terminated
with an appropriate acoustic resistance.
[0025]
The connection pipe 2 communicates with the probe pipe 1. The connection pipe 2 connects the
probe pipe 1 and the speaker 6.
[0026]
The material of the connection pipe 2 is, for example, a synthetic resin. The connecting pipe 2 is
an elongated tubular shape. The connecting pipe 2 is provided with a circular internal space of
an inner diameter d2 in a cross-sectional view in a direction orthogonal to the longitudinal
direction of the connecting pipe 2. The inner diameter d2 of the connection tube 2 is the same as
the inner diameter d1 of the probe tube 1. The length L2 in the longitudinal direction of the
connection pipe 2 is set based on the frequency band of the sound wave collected by the
measurement unit 3. The front end of the connection pipe 2 is connected to the rear end of the
probe pipe 1.
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[0027]
Here, the longitudinal direction of the connecting pipe 2 is a direction connecting the front end
and the rear end of the connecting pipe 2 when the connecting pipe 2 is formed into a straight
pipe. Further, that the probe tube 1 and the connection tube 2 communicate with each other
means that the sound wave P1 which has entered the probe tube 1 from the front end of the
probe tube 1 and travels the inside of the probe tube 1 as described later The probe tube 1 and
the connection tube 2 are in a connected state so as to advance the
[0028]
The material of the connection pipe 2 may be metal or the like.
[0029]
In addition, the connection tube 2 may be tubular so that the sound wave P1 can travel.
[0030]
Furthermore, a connection portion between the probe tube 1 and the connection tube 2
(hereinafter referred to as connection portion C .
In the aspect of), the probe tube 1 and the connection tube 2 may be in communication with each
other.
That is, for example, a connection member such as a joint may be interposed between the rear
end of the probe tube 1 and the front end of the connection pipe 2.
[0031]
Furthermore, an acoustic resistance material made of a sponge or the like may be filled in at least
a part of the internal space of the connection pipe 2. By filling the internal space of the
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connection pipe 2 with an acoustic resistance material and adjusting the acoustic impedance in
the connection pipe 2, it is possible to shorten the length L2 in the longitudinal direction of the
connection pipe 2.
[0032]
The measurement unit 3 picks up the sound wave P1 traveling in the probe tube 1.
[0033]
The measuring unit 3 is disposed at the connecting portion C.
That is, the measurement unit 3 is disposed on one end (front end) side of the connection pipe 2.
The connecting portion C is provided with a through hole penetrating the outer peripheral wall
of the connecting portion C and the probe tube 1 and the connecting tube 2 around the
connecting portion C. The measuring unit 3 is fitted in the through hole. A portion for collecting
the sound wave of the measurement unit 3 (hereinafter referred to as a "sound collecting
portion". ) Communicates with the internal space of the connection portion C.
[0034]
The measurement unit 3 may be disposed at the connecting portion C in a manner capable of
collecting the sound wave P1 traveling in the probe tube 1. That is, for example, a
communication member such as a pipe or a joint may be interposed between the internal space
of the connecting portion C and the sound collecting portion of the measuring unit 3. In addition,
the measurement unit 3 may be spaced apart on the side of the connection portion C.
[0035]
The detection unit 4 picks up the sound wave P1 traveling in the connection pipe 2.
[0036]
The detection unit 4 is disposed on the other end (rear end) side of the connection pipe 2.
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A through hole penetrating the outer peripheral wall of the connection pipe 2 is provided on the
rear end side of the connection pipe 2. The detection unit 4 is fitted in the through hole of the
connection pipe 2. The sound collection unit of the detection unit 4 communicates with the
internal space of the connection pipe 2.
[0037]
The detection unit 4 may be disposed on the rear end side of the connection pipe 2 in such a
manner that the sound wave P1 traveling in the connection pipe 2 can be collected. That is, for
example, a communication member such as a pipe or a joint may be interposed between the
internal space of the connection pipe 2 and the sound collecting portion of the detection unit 4.
In addition, the detection unit 4 may be spaced apart on the side of the connection pipe 2.
[0038]
The measurement unit 3 and the detection unit 4 are, for example, nondirectional condenser type
microphone units.
[0039]
The method of electroacoustic conversion between the measuring unit 3 and the detecting unit 4
is not limited to the capacitor type, and may be a dynamic type.
Further, the directivity between the measurement unit 3 and the detection unit 4 is not limited to
non-directional. Furthermore, the system and directivity of the electroacoustic conversion of the
measurement unit 3 may be the same as or different from the system and directivity of the
electroacoustic conversion of the detection unit 4.
[0040]
The signal generation unit 5 generates a cancellation signal based on the sound wave P1
collected by the detection unit 4. The signal generation unit 5 converts the phase of the electric
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signal corresponding to the sound wave P1 into the opposite phase (antiphase). The opposite
phase electric signal is a cancellation signal.
[0041]
The speaker 6 cancels the sound wave P1 traveling in the connection pipe 2 based on the cancel
signal (hereinafter referred to as sound wave P2 ). ) Is output into the connection pipe 2.
[0042]
The speaker 6 is a part that outputs the sound wave P2 (hereinafter referred to as a sound
emitting surface . ) Is disposed at the rear end of the connecting pipe 2 with the connecting
pipe 2 facing inward. That is, the sound emission surface of the speaker 6 is disposed on the
connection pipe 2 so as to face the front end side of the connection pipe 2. The sound emitting
surface communicates with the internal space of the connection pipe 2. The rear end of the
connection pipe 2 is closed by the speaker 6. Here, in the arrangement where the sound emitting
surface of the speaker 6 faces the front end side of the connection pipe 2, the sound wave P 2
output from the speaker 6 is inside the connection pipe 2 and from the rear end of the
connection pipe 2 to the front end of the connection pipe 2 An arrangement that travels towards
That is, in the connection pipe 2, the traveling direction of the sound wave P2 is reverse to the
traveling direction of the sound wave P1.
[0043]
In the longitudinal direction of the connection pipe 2, the distance D21 from the measurement
unit 3 to the speaker 6 is longer than the distance D11 from the measurement unit 3 to the
detection unit 4.
[0044]
In the longitudinal direction of the connection pipe 2, the distance D11 from the measurement
unit 3 to the detection unit 4 is longer than the distance D31 from the detection unit 4 to the
speaker 6.
[0045]
The speaker 6 is, for example, a dynamic speaker.
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[0046]
The speaker 6 may be disposed at the rear end of the connection pipe 2 in such a manner that
the sound wave P2 can be output into the connection pipe 2.
That is, for example, a communication member such as a pipe or a joint may be interposed
between the speaker 6 and the rear end of the connection pipe 2.
Moreover, the system of the electroacoustic conversion of the speaker 6 may be a capacitor type
or the like.
Further, a speaker that outputs the sound wave P2 may be disposed on the connection pipe 2 so
as to face the detection unit 4.
[0047]
The case 7 accommodates the connection pipe 2, the measurement unit 3, the detection unit 4,
the signal generation unit 5, and the speaker 6. The material of case 7 is, for example, a synthetic
resin. The case 7 has a shape suitable for the handling (handling) of the probe microphone M1,
for example, a substantially cylindrical shape.
[0048]
FIG. 2 is a schematic view showing another embodiment of the probe microphone according to
the present invention. The probe microphone M2 is disposed on the connection tube 2a so that
the speaker 6a that outputs the sound wave P2 faces the detection unit 4. That is, in the speaker
6a, the connecting pipe 2a is such that the distance D22 from the measuring unit 3 to the
speaker 6a is the same as the distance D12 from the measuring unit 3 to the detecting unit 4 in
the longitudinal direction of the connecting pipe 2a. Will be placed. The probe tube 1
constituting the probe microphone M2, the measuring unit 3, the detecting unit 4, the signal
generating unit 5 and the case 7 are the same as those constituting FIG.
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[0049]
The probe microphone M2 shown in the same figure is different from the probe microphone M1
shown in FIG. 1 in the arrangement of the speakers 6a. On the rear end side of the connection
pipe 2a, a through hole penetrating the outer peripheral wall of the connection pipe 2a is
provided at a position facing the detection unit 4. The speaker 6a is fitted in the through hole.
The sound emission surface of the speaker 6a communicates with the internal space of the
connection pipe 2a.
[0050]
At least one speaker 6a may be disposed on the connection pipe 2a so as to sandwich the
connection pipe 2a. Moreover, the speaker 6a should just be arrange ¦ positioned at the
connection pipe 2a in the aspect which can output the sound wave P2 in the connection pipe 2a.
That is, for example, a communication member such as a pipe or a joint may be interposed
between the speaker 6a and the rear end of the connection pipe 2a.
[0051]
Operation of Probe Microphone Next, the operation of the probe microphone M1 will be
described with reference to FIG.
[0052]
First, the front end of the probe tube 1 is brought close to the sound source S.
The sound wave P1 from the sound source S enters the probe tube 1 from the tip of the probe
tube 1. The sound wave P <b> 1 entering the probe tube 1 travels in the probe tube 1 toward the
rear end of the probe tube 1. The sound wave P <b> 1 traveling in the probe tube 1 is collected at
the connection portion C by the measurement unit 3.
[0053]
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As described above, the inner diameter d1 of the probe tube and the inner diameter d2 of the
connection tube 2 are the same. Therefore, the sectional area in front of the internal space of the
connecting portion C (the sectional area on the probe tube 1 side of the internal space of the
connecting portion C) is the sectional area after the internal space of the connecting portion C
(the internal space of the connecting portion C It is the same as the cross-sectional area of the
connecting pipe 2 side. The acoustic impedance in front of the internal space of connection C is
the same as the acoustic impedance in the internal space of connection C. Accordingly, the sound
wave P <b> 1 travels into the connecting pipe 2 without being reflected at the front end side of
the probe pipe 1 at the rear end of the probe pipe 1.
[0054]
Next, the sound wave P <b> 1 traveling in the connection pipe 2 is collected by the detection unit
4 at the rear end side of the connection pipe 2. The detection unit 4 generates an electrical signal
according to the collected sound wave P 1, and outputs the electrical signal to the signal
generation unit 5. The signal generation unit 5 generates an electric signal having a reverse
phase to the signal input from the detection unit 4, that is, a cancel signal, and outputs the
generated cancellation signal to the speaker 6. The speaker 6 generates a sound wave P2 based
on the cancellation signal and outputs the sound wave P2 to the internal space of the connection
pipe 2.
[0055]
The sound wave P 2 travels in the connecting pipe 2 toward the front end of the connecting pipe
2. That is, the traveling direction of the sound wave P1 is different from the traveling direction of
the sound wave P2. Further, the sound wave P2 has a phase opposite to that of the sound wave
P1 and the same sound pressure as the sound wave P1.
[0056]
In the vicinity of the speaker 6, the sound wave P2 mutually cancels out with the sound wave P1.
That is, the sound wave P2 cancels (cancels) the sound wave P1 in the connection pipe 2. As a
result, the sound wave P1 does not reach the rear end of the connection pipe 2 and is not
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reflected by the rear end of the connection pipe 2 to the front end side of the connection pipe 2.
Therefore, the reflected wave of the sound wave P1 from the rear end of the connection pipe 2 is
not generated. In addition, since a reflection wave of the sound wave P1 is not generated, a
standing wave is not generated.
[0057]
Thus, by eliminating the reflected wave of the sound wave P1 from the rear end of the
connecting pipe 2, the connecting pipe 2 is in the same state as the state in which the length L2
in the longitudinal direction is infinitely long. That is, the cancel unit corresponds to the
impedance matching tube communicated with the probe tube of the conventional probe
microphone. This state is maintained even if the length L2 in the longitudinal direction of the
connection pipe 2 is shortened as long as the sound wave P2 cancels the sound wave P1. As a
result, the length L2 in the longitudinal direction of the connection pipe 2 is shortened.
[0058]
According to the embodiment described above, the probe microphone M1 includes a cancel unit,
and outputs the sound wave P2 corresponding to the cancel signal generated based on the sound
wave P1 into the connection pipe 2. The sound wave P1 is canceled by the sound wave P2 in the
connection pipe 2. As a result, the sound wave P <b> 1 is not reflected to the front end side of the
connection pipe 2 at the rear end of the connection pipe 2. That is, the reflected wave of the
sound wave P1 is not generated in the connection pipe 2.
[0059]
As described above, the probe microphone according to the present invention does not generate
the reflected wave of the sound wave P1 by outputting the sound wave P2 according to the
cancellation signal to cancel the sound wave P1. That is, the probe microphone according to the
present invention does not generate the reflected wave of the sound wave P1 regardless of the
length of the connecting tube in the longitudinal direction. That is, the probe microphone
according to the present invention achieves sound collection suitable for measurement, is free
from the influence of the reflected wave of the sound wave from the sound source traveling in
the probe tube, and is smaller than the conventional probe microphone. it can.
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[0060]
The measurement unit 3 is disposed at the connection portion C, that is, at one end side of the
connection pipe 2. Further, the detection unit 4 is disposed on the other end side of the
connection pipe 2. That is, the measurement unit 3 and the detection unit 4 are separately
disposed at both ends of the connection pipe 2. According to this configuration, the measurement
unit 3 and the detection unit 4 are accommodated in the case 7 without interfering with each
other. That is, according to the present invention, the probe microphone can be miniaturized.
[0061]
In the longitudinal direction of the connection pipe 2, the distance D21 from the measurement
unit 3 to the speaker 6 is longer than the distance D31 from the measurement unit 3 to the
detection unit 4. Therefore, the position where the sound wave P2 cancels the sound wave P1
can be arbitrarily set between the detection unit 4 and the speaker 6.
[0062]
In the longitudinal direction of the connection pipe 2, the distance D11 from the measurement
unit 3 to the detection unit 4 is longer than the distance D31 from the detection unit 4 to the
speaker 6. Therefore, the position where the detection unit 4 picks up the sound wave P1 and the
position where the sound wave P2 cancels the sound wave P1 are close to each other. Therefore,
the accuracy with which the probe microphone M1 cancels the sound wave P1 is improved.
[0063]
Further, as shown in FIG. 2, in the speaker 6 a, the distance D22 from the measuring unit 3 to the
speaker 6 a is the same as the distance D12 from the measuring unit 3 to the detecting unit 4 in
the longitudinal direction of the connection tube 2. It may be disposed in the connecting pipe 2a
so that According to this configuration, the detection unit 4 and the speaker 6a can be disposed
close to each other. Further, the position where the detection unit 4 picks up the sound wave P1
is substantially the same as the position where the sound wave P2 cancels the sound wave P1.
That is, the timing at which the detection unit 4 picks up the sound wave P1 is substantially the
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same as the timing at which the sound wave P2 cancels the sound wave P1. Therefore, in control
in which the probe microphone M2 cancels the sound wave P1, there is no time difference
between the collection of the sound wave P1 and the cancellation of the sound wave P1.
[0064]
Since the traveling direction of the sound wave P2 is different from the traveling direction of the
sound wave P1, the sound wave P2 can efficiently cancel the sound wave P1 in the connecting
pipe 2.
[0065]
In the embodiment described above, the probe tube 1 and the connection tube 2 are separate
members, but in the probe microphone according to the present invention, the probe tube and
the connection tube may be integral.
In this case, in one tubular body, the portion from one end where the sound wave from the sound
source enters to the portion where the measurement unit is disposed corresponds to the probe
tube described in the present embodiment, and the remaining portion is the one. Corresponds to
the connecting pipe. Also in the probe microphone of this configuration, the acoustic impedance
is constant near the measurement unit.
[0066]
DESCRIPTION OF SYMBOLS 1 probe tube 2 connection tube 3 microphone unit for measurement
4 microphone unit for detection 5 signal generation unit 6 speaker 7 case 10 acoustic resistance
material M 1 probe microphone d 1 inner diameter d 2 of probe tube inner diameter L 1 of
connecting tube length L 2 of probe tube connecting tube Length D11 Distance from
measurement microphone unit to detection microphone unit D21 Distance from measurement
microphone unit to speaker D31 Distance from detection microphone unit to speaker D12
Distance from measurement microphone unit to detection microphone unit D22 Distance from
measurement microphone unit to speaker
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