JP2010091399A - Acoustic characteristic measuring device and method of measuring acoustic characteristic - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein it has been difficult to measure acoustic characteristics of a measurement target accurately for the already installed measurement target. <P>SOLUTION: An acoustic characteristic measuring device includes: an acoustic pipe communicating from a first opening to a second one with nearly the same diameter; a speaker that is connected to the first opening and outputs measurement sound into the acoustic pipe; an acoustic characteristic sensor for measuring acoustic characteristics of measurement sound in the acoustic pipe; and an extension pipe that communicates from a third opening detachable to the second opening to a fourth one and guides the advance direction of measurement sound in a direction different from the advance direction of measurement sound within the acoustic pipe between the third and fourth openings. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an acoustic characteristic measuring apparatus and an acoustic characteristic measuring method for outputting a measurement sound from one side of an acoustic tube and measuring an acoustic characteristic of a measurement object attached to the other side.

Conventionally, a normal incident sound absorption coefficient measurement method (JIS A 1405) and a reverberation chamber method sound absorption coefficient measurement method (JIS A 1409) are known as methods for measuring acoustic characteristics of a material such as the sound absorption coefficient of a sound absorbing material. Moreover, in these known methods, it is difficult to measure the acoustic characteristics of a material that has been installed in the same state as actually used. Attempts have been made to measure the sound absorption coefficient of installed material by measuring with a single microphone (for example, Patent Document 1).
JP-A-62-161021

In the prior art, it has been difficult to accurately measure the acoustic characteristics of a measurement target that has been installed in the same state as that actually used.
That is, since the number of microphones (sensors) for measuring the reflected sound is limited to a finite number, only the reflected sound in the direction of the installed microphone can be evaluated. For this reason, the accuracy of measurement of acoustic characteristics is insufficient for materials that change and disperse in the direction of the reflected sound different from the incident sound, such as resonators and scatterers. In addition, when the measurement target is already installed, the reflected sound from a part other than the measurement target (for example, a ceiling or a wall near the measurement target) is also measured in addition to the sound reflected from the measurement target. . Therefore, it is difficult to remove the reflected sound from the part other than the measurement target in the installed site, and it is difficult to accurately measure the acoustic characteristics of the measurement target.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique capable of accurately measuring an acoustic characteristic of an installed measurement object.

  In order to achieve the above object, in the present invention, a speaker is connected to the first opening of the acoustic tube that communicates from the first opening to the second opening, and the acoustic characteristics of the measurement sound in the acoustic tube are measured. In the configuration measured by the acoustic characteristic sensor, the extension tube is configured to be detachable from the second opening of the acoustic tube. Here, the extension tube communicates from the third opening to the fourth opening, and the traveling direction of the measurement sound is different from the traveling direction of the measurement sound in the acoustic tube between the third opening and the fourth opening. It is configured to guide in the direction.

  That is, the extension tube is configured to vary the traveling direction of the measurement sound in the acoustic tube. With this configuration, when the extension tube is attached to the acoustic tube, the inner wall of the extension tube is different from the inner wall of the acoustic tube. They extend in different directions or have different shapes. As a result, the fourth opening serving as a part to which the measurement target is attached opens in a direction different from the extending direction of the second opening, or has a different shape. For this reason, even if there is a measurement target that cannot be directly attached to the second opening of the acoustic tube when assuming a measurement target having an arbitrary shape and size and an arbitrary ambient environment, the extension tube is attached. (Possibly) Therefore, according to the configuration of the present invention, the acoustic characteristic measurement device can be attached to a measurement object different from the measurement object corresponding to the shape of the second opening, and the measurable material or the measurable installation condition. The degree of freedom increases.

  If the acoustic tube can be attached to the measurement target via the extension tube, it is possible to measure the acoustic characteristics of the measurement sound output from the speaker in a state where noise is excluded. Therefore, it is possible to accurately assume the acoustic characteristics of the measurement target. In addition, since the extension tube can be attached to and detached from the second opening of the acoustic tube, a plurality of extension tubes of various shapes are prepared in advance, and any extension tube selected from them is prepared. By adopting a configuration that is attached to the acoustic tube, it is possible to measure an extremely large number of various types of measurement objects.

  Here, the acoustic tube is a cylindrical body that is open at both ends to form a first opening and a second opening, and communicates with substantially the same diameter, so that a one-dimensional measurement sound ( That is, it is only necessary to excite a measurement sound consisting of plane waves having the same phase in a plane perpendicular to the direction in which the acoustic tube extends. Therefore, the axis in the direction in which the acoustic tube extends is preferably linear, but the cross-sectional shape when cut in a direction perpendicular to the axis is not particularly limited, and various shapes such as a square such as a square and a circle are possible. It can be adopted. Of course, in order to excite the one-dimensional measurement sound, the acoustic tube is made of a rigid body, the inner wall is made smooth (a structure without gaps or irregularities), or made of a sound insulating material (for example, metal). May be.

  Moreover, the speaker should just be connected to the 1st opening part of an acoustic tube, and can output a measurement sound in the said acoustic tube. In other words, the speaker need only be connected to output measurement sound into the acoustic tube from the first opening and excite the one-dimensional measurement sound in the acoustic tube, and the diameter, material, and output of the speaker can be adjusted as appropriate. It is. In addition, the connection portion between the speaker and the first opening is preferably hermetically sealed, but may have various configurations such as a hole being formed in the acoustic tube as long as one-dimensional measurement sound can be excited. The tube that guides the output sound of the speaker to the first opening may be configured integrally with the output of the speaker and connected to the first opening.

  The acoustic characteristic sensor only needs to be able to measure the acoustic characteristic of the measurement sound in the acoustic tube, and various sensors such as a microphone that measures sound pressure and an acoustic particle velocity probe that measures acoustic particle velocity can be used. In addition, the acoustic characteristics may be measured directly or indirectly by an acoustic characteristic sensor. In addition to sound pressure and acoustic particle velocity, acoustic impedance, acoustic admittance, acoustic intensity, sound absorption rate, Various characteristics such as reflectance can be measured as acoustic characteristics.

  The extension tube has a third opening that can be attached to and detached from the second opening of the acoustic tube, communicates from the third opening to the fourth opening, and changes the traveling direction of the measurement sound in the extension tube. I can do it. That is, it is only necessary that the extension tube can be attached to the acoustic tube so that the inner wall of the extension tube is different from the state in which the inner wall of the acoustic tube is extended.

  For example, the shape of the inner diameter in the extension pipe may be changed by communicating the fourth opening and the third opening of the extension pipe so as to have different shapes. Since the third opening is connected to the second opening, the shape of the fourth opening, which is different from the shape of the third opening, is different from the shape of the second opening. For this reason, it becomes possible to attach a 4th opening part about the measuring object of a shape different from the shape of the 2nd opening part of an acoustic tube, and to measure an acoustic characteristic.

  Here, the fourth opening has a shape different from that of the third opening, and is considered to have a different shape when both are shapes other than the same. Therefore, not only when the third opening and the fourth opening are non-similar, but also when they are similar but different in size. As the latter, for example, a configuration in which the inner diameter of a circle or rectangle increases or decreases from the third opening toward the fourth opening can be employed.

  Further, if the direction in which the extension tube extends from the third opening toward the fourth opening is different from the direction in which the acoustic tube extends, the second opening with the acoustic characteristic measuring device installed at a predetermined position. The fourth opening can be made to correspond to a measurement object that exists in a different position or a measurement object that faces in a different direction. For this reason, it becomes possible to measure about the measuring object of various positions and directions by attaching the 4th opening to the measuring object concerned. Here, it is only necessary that the direction in which the extension tube extends differs from the direction in which the acoustic tube extends, and the inner diameter of the extension tube may be the same or fluctuate from the third opening to the fourth opening. good.

  Furthermore, the extension tube may be configured to have flexibility. That is, it is difficult to give the acoustic tube flexibility in order to excite the one-dimensional measurement sound, but by making the extension tube existing between the acoustic tube and the measurement object flexible, Although it is difficult to stably generate a one-dimensional measurement sound in the extension pipe, the degree of freedom of attachment to the measurement object can be increased. Here, it is sufficient that the degree of freedom of attachment to the measurement object can be increased, and the direction of the extension tube can be bent between the third opening and the fourth opening, and the shape of the fourth opening Various configurations, such as a configuration that can be deformed, can be employed. Note that the extension tube is preferably shorter than the acoustic tube in order to suppress one-dimensional measurement sound disturbance in the acoustic tube.

  Furthermore, in the configuration of various extension pipes as described above, the extension pipe may be configured to be separable and connectable between the third opening and the fourth opening. That is, the extension pipe may be configured by connecting a plurality of pipe bodies. In this case, the length of the extension tube and the shape and size of the fourth opening can be varied by appropriately selecting the tube to be connected. In addition, the direction in which the extension pipe extends can be changed a plurality of times.

  Furthermore, it is good also as a structure which acquires acoustic absorption characteristic of a measuring object by measuring acoustic impedance with an acoustic characteristic sensor. For example, it is possible to employ a configuration in which the representative value is obtained by measuring the acoustic impedance at different positions in the plane perpendicular to the axis in the direction in which the acoustic tube extends with the measurement target attached to the fourth opening. is there. According to this configuration, even if the measurement target has different acoustic characteristics for each position (for example, the measurement target having non-uniform reflection sound characteristics in a plane perpendicular to the axis in the direction in which the acoustic tube extends), Therefore, by substituting the representative value into a known equation (for example, see JIS A 1405-2), sound absorption characteristics (sound absorption coefficient α and reflectance r (r = 1−α)) Either or both).

  That is, in a known acoustic characteristic measuring device using an acoustic tube, a material that measures sound pressure etc. exclusively at one point and can be attached in a state having uniform acoustic characteristics over the entire opening of the acoustic tube (for example, , Glass wool, etc.) are assumed. However, according to the configuration in which the representative value is obtained by measuring the acoustic impedance at different positions in the plane perpendicular to the axis in the direction in which the acoustic tube extends, the measurement object (for example, a plate) with different acoustic characteristics for each position is obtained. The sound absorption characteristics can be specified even for a vibration sound absorber. The representative value may be a value that represents the acoustic characteristic of the measurement target attached to the fourth opening, and various values such as an average value and a median value can be adopted.

  In the above configuration, a publicly known formula into which the representative value Z of acoustic impedance is substituted is, for example, Z = ρc (1 + r) / (1-r) (where ρc is a characteristic impedance, and r is a reflection) In this equation, the distance between the acoustic measurement sensor and the measurement object is not included in the parameters. Therefore, it is possible to measure the acoustic characteristics of the measurement object without measuring the distance between the acoustic measurement sensor and the measurement object. For this reason, the acoustic characteristic identification method using the above formula is based on the present invention in which the distance between the acoustic measurement sensor installed in the acoustic tube and the measurement target can be changed by selecting a detachable extension tube. This is a very suitable specific method.

  Furthermore, it is good also as a structure which acquires acoustic absorption characteristic of a measuring object by measuring acoustic intensity with an acoustic characteristic sensor. For example, the sound intensity is measured in a state where the measurement target, the substantially complete sound absorber, and the substantially complete reflector are attached to the fourth opening, and the sound intensity of the substantially complete sound absorber and the substantially complete reflector is used as a reference. Therefore, it is possible to adopt a configuration for acquiring the sound absorption characteristics of the measurement object.

That is, the sound intensity includes an incident wave (sound wave output from the speaker) from the first opening to the second opening and a reflected wave (from the second opening to the first opening) (to the fourth opening). Therefore, the sound absorption characteristic of the measurement target cannot be specified simply by measuring the sound intensity I of the measurement target. Therefore, if the sound intensity I _{A of} the substantially perfect sound absorber and the sound intensity I _R of the substantially perfect reflector are measured, the sound absorption characteristic is expressed as reflectance r = (I _A −I) / (I _A −I _R ). Can be acquired. Note that obtaining the reflectance r is equivalent to obtaining the sound absorption coefficient α (α = 1−r).

  Also, in the acoustic characteristic identification method based on the acoustic intensity as described above, the acoustic characteristic can be identified without identifying the distance between the acoustic measurement sensor and the measurement target. Therefore, this identification method is a very suitable identification method for the present invention in which the distance between the acoustic measurement sensor installed in the acoustic tube and the measurement object can be changed by selecting a detachable extension tube. The substantially complete sound absorber described above is a material having a higher sound absorption rate than the measurement target, and may be any material that can substantially ignore the reflected energy for the measurement sound in the frequency range of the measurement target. For example, a porous sound absorption material ( Glass wool or the like formed into a wedge shape can be used as a substantially complete sound absorber. The substantially perfect reflector described above is a material having a higher reflectance than the measurement target, and may be any material that can be regarded as reflecting almost all energy for the measurement sound in the frequency range of the measurement target. An iron plate or a resin plate having a thickness of 1 mm can be used as a substantially complete sound absorber.

  Furthermore, it is good also as a structure which acquires a sound absorption characteristic with a transfer function method. For example, in a state where the measurement target is attached to the fourth opening, the sound absorption characteristics of the measurement target are measured by measuring the sound pressure with the first microphone and the second microphone closer to the fourth opening than the first microphone. The configuration to acquire can be adopted.

  That is, if the sound pressure is measured by the output signals of the first microphone and the second microphone installed at two locations, the transfer function from the position of the first microphone to the position of the second microphone is calculated based on the sound pressure at each position. Can be acquired. If the transfer function can be specified, the sound absorption characteristic can be acquired based on the transfer function, the distance from the first microphone to the second microphone, and the distance from the measurement target to the first microphone. According to this method, it is possible to measure the acoustic characteristics when the extension tube is used by the same measurement method as the sound absorption characteristics such as the normal incident sound absorption coefficient defined in the JIS standard.

  Furthermore, the present invention can be applied to an acoustic characteristic measuring method for measuring an acoustic characteristic of a measurement target by attaching an extension pipe to the acoustic pipe, in addition to the acoustic characteristic measuring apparatus. Moreover, the acoustic characteristic measuring apparatus as described above may be realized as a single acoustic characteristic measuring apparatus or may be realized as a part of another apparatus, and includes various aspects.

Here, embodiments of the present invention will be described in the following order.
(1) Configuration of acoustic characteristic measuring device:
(2) Measurement of acoustic characteristics:
(3) Other embodiments:

(1) Configuration of acoustic characteristic measuring device:
FIG. 1A is a diagram showing a configuration of an acoustic characteristic measuring apparatus according to the present invention, and is a cross-sectional view showing a cylindrical body constituting the acoustic characteristic measuring apparatus cut along a plane parallel to its axis. The acoustic characteristic measuring apparatus 10 according to the present embodiment includes an acoustic tube 11, a speaker 12, a microphone 13a, an acoustic particle velocity probe 13b, a control unit 13, and an extension tube 14. The acoustic tube 11 is a metal cylindrical body. In this embodiment, the acoustic tube 11 includes an inner wall and an outer wall that are formed concentrically around a linearly extending axis, have an inner diameter substantially the same, and both axial ends. Open at the part. In this example, the opening on the right side of the paper is called the first opening 11a, and the opening on the left of the paper is called the second opening 11b.

  The speaker 12 is attached to a speaker case 12a having a shape in which one end of a cylindrical body is open and the other end is closed. Further, the diameter of the speaker 12 is substantially the same as the inner diameter of the first opening 11a, and the outer diameter of the speaker case 12a and the outer diameter of the acoustic tube 11 are substantially the same. In the present embodiment, the speaker case 12a is connected to the acoustic tube 11, whereby the speaker 12 is connected to the first opening portion 11a. The speaker 12 is connected to a connection line extending from the control unit 13, is driven by power supplied by the control unit 13, and outputs a measurement sound corresponding to a control signal output from the control unit 13. As a result, the measurement sound output from the speaker 12 proceeds as a one-dimensional measurement sound in the acoustic tube.

  In the acoustic tube 11, the microphone 13a and the acoustic particle velocity probe 13b are supported by a support unit (not shown) so that the position thereof can be changed. Here, it is only necessary that the support unit supports the microphone 13a and the acoustic particle velocity probe 13b, changes the position in a plane perpendicular to the axis of the acoustic tube 11, and fixes the microphone 13a and the acoustic particle velocity probe 13b at a desired position. For example, a configuration in which the microphone 13a and the acoustic particle velocity probe 13b are attached to the tip of a thin rod extending from the outer peripheral side to the inner peripheral side of the acoustic tube 11 in a direction parallel to a plane perpendicular to the axis of the acoustic tube 11 can be employed. .

  The microphone 13a and the acoustic particle velocity probe 13b are connected to the control unit 13 by a connection line, the microphone 13a outputs a signal corresponding to the sound pressure to the control unit 13, and the acoustic particle velocity probe 13b is an acoustic particle. A signal corresponding to the speed is output to the control unit 13. The control unit 13 includes a CPU, a ROM, a RAM, and the like (not shown) and can execute a program for measuring acoustic characteristics.

  In this embodiment, the acoustic characteristic acquisition unit 13c can be executed as a part of the function of this program. The acoustic characteristic acquisition unit 13c is a module that executes a process of acquiring acoustic impedance based on output signals of the microphone 13a and the acoustic particle velocity probe 13b and acquiring sound absorption characteristics based on the acoustic impedance. That is, the control unit 13 calculates the sound absorption characteristic of the measurement target by the process of the acoustic characteristic acquisition unit 13c. Details of the measurement will be described later.

  In this embodiment, the extension pipe 14 is a resin-made cylindrical body, and the extension pipe 14 shown in FIG. 1A extends in a direction different from the extension direction of the shaft of the acoustic pipe 11 and gradually has a diameter from one end to the other end. It is comprised so that it may become large. The extension tube 14 is open at both ends, and in this example, the opening on the right side of the drawing is called a third opening 14a, and the opening on the left side of the drawing is called a fourth opening 14b.

  In this embodiment, the 3rd opening part 14a of the extension pipe 14 is the same diameter as the 2nd opening part 11b, and it connects while facing both. Therefore, by the connection, the acoustic tube 11 and the extension tube 14 become a single tubular body communicating with each other. The fourth opening 14b is larger than the third opening 14a and has a different shape. Therefore, the fourth opening 14b and the second opening 11b have different shapes. A resin O-ring 15 is attached to the edge of the fourth opening 14 b, and the acoustic characteristic measuring device 10 is placed against the measurement target 20 while the O-ring 15 is in contact with the measurement target 20. It is designed to be attached.

  For this reason, in the example shown in FIG. 1A, the measurement is performed with the extension tube 14 interposed between the acoustic tube 11 and the measurement target 20. Here, since the fourth opening 14b has a shape that is significantly different from the diameter of the second opening 11b, the extension tube 14 is used even when the measurement target 20 is larger than the second opening 11b of the acoustic tube 11. This makes it possible to measure the sound absorption characteristics of the measurement object 20.

  Furthermore, the shape of the extension pipe 14 shown in FIG. 1A is an example, and in this embodiment, a plurality of extension pipes are prepared in advance and can be exchanged. That is, in the present embodiment, a plurality of extension pipes are prepared in advance so that the third opening, which is the opening on one side, can be attached to and detached from the second opening 11b. 1B, 1C, and 2A to 2C show examples of various extension pipes.

  The extension tube 140 shown in FIG. 1B is made of a flexible material, and the inner diameter of the fourth opening 140b is larger than the inner diameter of the third opening 140a. In this configuration, the extension tube 140 can be attached to the measurement target 200 while deforming the shape of the fourth opening 140b, and the sound absorption of the measurement target 200 having a complicated two-dimensional or three-dimensional shape is possible. It becomes possible to measure the characteristics.

  The extension pipe 141 shown in FIG. 1C is also made of a flexible material and has substantially the same inner diameter from the third opening 141a to the fourth opening 141b. According to this configuration, it is possible to attach the extension tube 141 to the measurement object 201 while deforming the tube wall between the third opening 141a and the fourth opening 141b, for example, by bending the tube wall. It is possible to measure the sound absorption characteristics of the measurement object 201 that does not exist in the extension direction of the shaft. This configuration is particularly suitable for application when movement is not easy, such as when the acoustic tube 11 is heavy. When the extension pipe is made of a flexible material, the extension pipe itself may be configured to be able to expand and contract, or may be provided with flexibility by an accordion-like configuration. It can be adopted.

  In the example shown in FIG. 2A, the extension tube 142 is configured by connecting a first extension tube 1421, a second extension tube 1422, and a third extension tube 1423. That is, the first extension pipe 1421, the second extension pipe 1422, and the third extension pipe 1423 are cylindrical bodies in which the inner diameter of one opening is larger than the inner diameter of the other opening, and the inner diameter gradually changes. The smaller opening in the first extension pipe 1421 and the larger opening in the second extension pipe 1422 can be connected with substantially the same diameter, and the smaller opening in the second extension pipe 1422 and the third opening can be connected. The larger opening in the extension pipe 1433 can be connected with substantially the same diameter.

  Therefore, in this example, by connecting the first extension pipe 1421, the second extension pipe 1422, and the third extension pipe 1423, one cylindrical body whose inner diameter gradually changes is configured to be the extension pipe 142. In this example, the smaller opening of the third extension tube 1423 and the second opening 11b of the acoustic tube 11 have substantially the same diameter and can be connected. Therefore, the smaller opening in the third extension tube 1423 becomes the third opening 142 a of the extension tube 142, and the larger opening in the first extension tube 1421 becomes the fourth opening 142 b of the extension tube 142.

  In the above configuration, the sound absorption characteristic can be measured for a measurement object larger than the second opening 11b of the acoustic tube 11. Of course, in the example shown in FIG. 2A, the extension tube may be configured by using one or both of the second extension tube 1422 and the third extension tube 1423, and the first extension tube 1421 is further different. An extension tube may be connected.

  In the example shown in FIG. 2B, the extension pipe 143 is configured by connecting a first extension pipe 1431 and a second extension pipe 1432. That is, the first extension pipe 1431 and the second extension pipe 1432 are cylindrical bodies having substantially the same inner diameter and curved in the direction in which the axis extends. Moreover, the internal diameter of the opening part of the 1st extension pipe 1431 and the 2nd extension pipe 1432 can be connected by substantially the same diameter. Therefore, in this example, by connecting the first extension pipe 1431 and the second extension pipe 1432, a cylindrical body having a constant inner diameter and changing the direction of the shaft is formed and becomes the extension pipe 143.

  In the present example, the opening portions of the first extension tube 1431 and the second extension tube 1432 and the second opening portion 11b of the acoustic tube 11 have substantially the same diameter and can be connected. Therefore, in the extension pipe 143 to which the first extension pipe 1431 and the second extension pipe 1432 are connected, one opening becomes the third opening 143a and the other opening becomes the fourth opening 143b. In the above configuration, the fourth opening 143b can be made to correspond to a measurement object that exists at a position different from the second opening 11b of the acoustic tube 11 or a measurement object that faces in a different direction. It becomes possible to perform measurement with respect to the measuring object of the direction. Of course, in the example shown in FIG. 2B, another extension pipe may be connected to the first extension pipe 1431 and the second extension pipe 1432, or the first extension pipe 1431 and the second extension pipe 1432 are connected. In this case, the direction is arbitrary, and the direction in which the extension pipe 143 extends can be set to a desired direction.

  In the example shown in FIG. 2C, the extension tube 144 is configured by slidably connecting the first extension tube 1441 to the fifth extension tube 1445. That is, the first extension pipe 1441 to the fifth extension pipe 1445 are cylindrical bodies, and the inner diameter of the nth extension pipe 144n is (n + 1) th extension pipe 144 (n + 1) when n is 1 to 5. The (n + 1) th extension tube 144 (n + 1) slightly larger than the outer diameter can be inserted into the nth extension tube 144n and slid. Therefore, in the present example, the first extension pipe 1441 to the fifth extension pipe 1445 constitute a cylindrical body that can be expanded and contracted to form the extension pipe 144.

  In this example, the opening of the fifth extension tube 1445 and the second opening 11b of the acoustic tube 11 have substantially the same diameter and can be connected. Therefore, in the extension pipe 144 connecting the first extension pipe 1441 to the fifth extension pipe 1445, the opening of the fifth extension pipe 1445 becomes the third opening 144a, and the opening of the first extension pipe 1441 is the fourth opening. 144b. In the above configuration, the sound absorption characteristic can be measured for a measurement target larger than the second opening 11b of the acoustic tube 11, and the distance between the acoustic tube 11 and the measurement target can be adjusted to a desired distance. Of course, in the example shown in FIG. 2C, any one of the first extension pipe 1441 to the fourth extension pipe 1444 or a plurality of them may be omitted, and an extension pipe having a larger inner diameter around the first extension pipe 1441. May be connected.

  In addition, the opening direction of the second extension pipe 1442 may be attached to the sound absorption target with the slide direction of the first extension pipe 1441 and the slide direction of the second extension pipe 1442 reversed. In the example shown in FIG. 2C, the first extension pipe 1441 is shown in a sectional view cut in a direction parallel to the axis, but the other second extension pipe 1442 to fifth extension pipe 1445 are not shown in the sectional view. Absent.

  In addition to the above examples, various configuration examples can be employed. For example, the extension tube may be configured such that the diameter of the fourth opening is smaller than that of the third opening. According to this configuration, even if the measurement object is attached to a narrow place where the acoustic tube 11 cannot be inserted, if the fourth opening can be inserted, the fourth opening is attached to the measurement object. It becomes possible to measure the characteristics. Furthermore, you may employ | adopt the structure which extracts and combines the arbitrary parts of the above-mentioned extension pipe | tube.

  As described above, according to the present embodiment, the fourth opening of the extension tube can be attached to the measurement object having various shapes attached at various positions different from the second opening 11b of the acoustic tube 11. Is possible. Therefore, it is possible to select an appropriate extension pipe at the site where the acoustic characteristics are to be measured, and to measure the acoustic characteristics of measurement objects having various positions and shapes.

(2) Measurement of acoustic characteristics:
Next, measurement of acoustic characteristics (sound absorption characteristics) in the above-described embodiment will be described. In this embodiment, first, a measurement target is attached to the fourth opening of the extension tube, and the microphone 13a and the acoustic particle velocity probe 13b are fixed at predetermined positions in a plane perpendicular to the axis of the acoustic tube 11. Sound is output from the speaker 12 in the state. In this state, the control unit 13 specifies the sound pressure p based on the output signal of the microphone 13a and the particle velocity v based on the output signal of the acoustic particle velocity probe 13b by the processing of the acoustic characteristic acquisition unit 13c. Here, the particle velocity v is a component in a direction parallel to the axis of the acoustic tube 11 (a component in a direction perpendicular to a plane on which the microphone 13a and the acoustic particle velocity probe 13b can be moved). Furthermore, the control part 13 acquires the acoustic impedance Z as Z = p / v by the process of the acoustic characteristic acquisition part 13c.

  In the present embodiment, the microphone 13a and the acoustic particle velocity probe 13b are fixed at a plurality of positions over almost the entire area in a plane perpendicular to the axis of the acoustic tube 11, and the acoustic impedance at each position is acquired to obtain a representative value ( For example, the average value of acoustic impedance at each position is acquired. Then, the representative value is Z, and the reflectance r is acquired by the equation Z = ρc (1 + r) / (1-r) that connects the acoustic impedance Z and the reflectance r (ρc is a characteristic impedance).

  According to the above processing, it is possible to measure the sound absorption characteristics of a measurement object having anisotropy in physical properties. Further, the above-described equation for connecting the acoustic impedance Z and the reflectance r does not include the distance between the acoustic measurement sensor (the microphone 13a or the acoustic particle velocity probe 13b) and the measurement target as a parameter. Therefore, it is possible to measure the sound absorption characteristics of the measurement object without measuring the distance between the acoustic measurement sensor and the measurement object. For this reason, the above method is a method suitable for application to the above-described embodiment in which a detachable extension tube is selected.

(3) Other embodiments:
The above embodiment is an example for carrying out the present invention, and various other configurations can be adopted as long as the extension tube is attached to the acoustic tube and the acoustic characteristics of the measurement target are measured. For example, the shape and configuration of the extension tube are not limited to the above example. Further, the acoustic characteristics of the measurement target are not limited to the reflectance r, but may be a sound absorption coefficient α (α = 1−r), and the acoustic impedance, acoustic admittance, acoustic intensity, sound pressure, and acoustic particle velocity can be set. The structure which acquires may be sufficient.

  Moreover, it is good also as a structure which acquires sound absorption characteristics, such as the reflectance r and the sound absorption coefficient (alpha), based on sound intensity. This configuration can be realized by a configuration substantially similar to the embodiment shown in FIG. 1A described above, but it is not essential that the microphone 13a and the acoustic particle velocity probe 13b are movable. It is sufficient if the microphone 13a and the acoustic particle velocity probe 13b are disposed in the center.

  In this configuration, the sound intensity is measured by outputting sound from the speaker 12 with the substantially complete sound absorber, the substantially complete reflector, and the measurement target attached to the fourth opening of the extension tube. That is, the control unit 13 specifies the sound pressure p based on the output signal of the microphone 13a and the particle velocity v based on the output signal of the acoustic particle velocity probe 13b by the processing of the acoustic characteristic acquisition unit 13c. Again, the particle velocity v is a component parallel to the axis of the acoustic tube 11. Furthermore, the control part 13 calculates p * v by the process of the acoustic characteristic acquisition part 13c, and acquires it as an acoustic intensity.

Here, if the acoustic intensity of the substantially perfect sound absorber is I _A , the acoustic intensity of the substantially perfect reflector is I _R , and the acoustic intensity of the measurement target is I, then (I _A −I) / (I _A − The reflectance r can be obtained as I _R ) = reflectance r. More specifically, based on the fact that the sound intensity is the difference between the sound intensity of the input sound wave and the sound intensity of the reflected sound wave, each sound intensity is expressed as I _A = I _iA −I _rA , I _R = I _iR −I _rR , I = I _i −I _r Substituting these into _{(I A -I) / (I} A -I R), = (I A -I) / (I A -I R) ((I iA -I rA) - (I i -I r )) / ((I _iA −I _rA ) − (I _iR −I _rR )). The above-mentioned input sound wave is a sound wave when the measurement sound output from the speaker 12 reaches the microphone 13a and the acoustic particle velocity probe 13b, and the above-described reflected sound wave is a sound wave reflected from the measurement object. It is a sound wave when it reaches the acoustic particle velocity probe 13b.

If the output level of the speaker 12 is set to a common level during the measurement of the sound intensity described above, the sound intensity of the input sound wave at the time of each sound intensity measurement is regarded as equal (I _iR = I _iA = I _i ). Can do. Therefore, applying this condition to the above formula, the _{(I A -I) / (I} A -I R) = (I r -I rA) / (I rR -I rA). The numerator on the right side of the equation is the acoustic intensity of the reflected sound wave to be measured—the acoustic intensity of the reflected sound wave of the substantially perfect sound absorber, and the denominator on the right side is the acoustic intensity of the reflected sound wave of the almost perfect reflector—approximately the perfect sound absorption. It is the sound intensity of the reflected sound wave of the body.

  Here, since the almost perfect sound absorber absorbs the input sound wave almost completely, the sound intensity of the reflected sound wave of the almost perfect sound absorber can be regarded as almost “0”, and the main component of the molecule on the right side is the reflection of the object to be measured. It can be regarded as the sound intensity of sound waves. On the other hand, since the nearly perfect reflector reflects the input sound wave almost completely, the sound intensity of the reflected sound wave of the almost perfect reflector can be regarded as almost equal to the sound intensity of the input sound wave, and the main component of the molecule on the right side is It can be regarded as the acoustic intensity of the reflected sound wave of the substantially perfect reflector.

Therefore, the main component of the right side (I _r −I _rA ) / (I _rR −I _rA ) of the above formula is (acoustic intensity of reflected sound wave to be measured) / (acoustic intensity of reflected sound wave of substantially perfect reflector). City). (Sound intensity of the reflected wave to be measured) / for equal to the reflectance (sound intensity of the reflected waves of the complete reflector), reflecting the above formula _{(I A -I) / (I} A -I R) It can be regarded as the rate r. Therefore, the control unit 13 performs the processing of the acoustic characteristic acquisition unit 13c to reflect the reflectance based on the acoustic intensity I _{A of} the substantially complete sound absorber, the acoustic intensity I _R of the substantially complete reflector, and the acoustic intensity I of the measurement target. Get r. In the almost full reflector, since the orientation and the sound intensity of the sound intensity and the reflected sound wave incident sound wave is substantially the same substantially opposite magnitude, the acoustic intensity I _R can be regarded as substantially zero. Therefore, the above equation _{(I A -I) / (I} A -I R) may regarded as the formula _{(I A -I) / I A} .

According to the above processing, it is possible to measure the sound absorption characteristics of a measurement object having anisotropy in physical properties. Further, in the above formula _{(I A -I) / (I} A -I R), the distance between the acoustic measurement sensor (microphone 13a and the acoustic particle velocity probe 13b) and the measurement object is not included as a parameter. Therefore, it is possible to measure the sound absorption characteristics of the measurement object without measuring the distance between the acoustic measurement sensor and the measurement object. For this reason, the above method is a method suitable for application to the above-described embodiment in which a detachable extension tube is selected.

The sensor for acquiring the sound intensity is not limited to the microphone 13a and the acoustic particle velocity probe 13b, and may be two microphones. That is, two microphones M ₁ and M ₂ are arranged side by side along the axial direction of the acoustic tube 11 (distance between the microphone M ₁ and the measurement object> distance between the microphone M ₂ and the measurement object). When the sound pressures p ₁ and p ₂ are measured by the microphones M ₁ and M ₂ , the sound pressure p = (p ₁ + p ₂ ) / 2 and the particle velocity v = (− ∫ (p ₂ −p ₁ ). It is possible to obtain acoustic intensity as dt) / ρd and I = p · v. Note that ρ is the air density, and d is the distance between the acoustic centers of the two microphones. When p and v (acoustic impedance) are measured using the _two microphones M ₁ and M ₂ as described above, the two microphones M ₁ and M ₂ are measured (measurement materials). It arrange | positions in the surface vicinity of 20.

Further, the sound absorption characteristics such as the reflectance r and the sound absorption coefficient α may be obtained by the transfer function method. That is, two microphones (first microphone M ₁ and second microphone M ₂ ) are arranged side by side along the axial direction of the acoustic tube 11. Here, (distance between the first microphone M ₁ and the fourth opening)> (distance between the second microphone M ₂ and the fourth opening). If the sound pressures p ₁ and p ₂ are measured by the first microphone M ₁ and the second microphone M ₂ , respectively, the transfer function H ₁₂ from the position of the first microphone M _{1 to} the position of the second microphone M ₂ is obtained. It is possible to obtain a transfer function as = p ₂ / p ₁ . If the transfer function H ₁₂ can be specified, the reflectance can be obtained as reflectance r = exp (2jkx ₁ ) · (H ₁₂ −H _I ) / (H _R −H ₁₂ ). Here, k is a wavelength constant, x ₁ is the distance between the first microphone and the measurement object, H _I = exp (−jks), H _R = exp (jks), and s is the first microphone M ₁ and the first microphone. 2 is the distance between the acoustic centers of the two microphones M ₂ .

(1A) is a figure which shows the structure of an acoustic characteristic measuring apparatus, (1B), (1C) is a figure which shows the example of an extension pipe | tube. (2A)-(2C) is a figure which shows the example of an extension pipe | tube.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Acoustic characteristic measuring apparatus, 11 ... Acoustic tube, 11a ... 1st opening part, 11b ... 2nd opening part, 12 ... Speaker, 13 ... Control part, 13a ... Microphone, 13b ... Acoustic particle velocity probe, 13c ... Acoustic characteristic Acquisition unit, 14 ... extension tube, 14a ... third opening, 14b ... fourth opening

Claims (10)

An acoustic tube communicating with the substantially same diameter from the first opening to the second opening;
A speaker connected to the first opening and outputting measurement sound into the acoustic tube;
An acoustic characteristic sensor for measuring an acoustic characteristic of the measurement sound;
The third opening that can be attached to and detached from the second opening is communicated from the fourth opening to the fourth opening, and the traveling direction of the measurement sound is set between the third opening and the fourth opening in the acoustic tube. An extension tube for guiding the measurement sound in a direction different from the traveling direction of the measurement sound,
An acoustic characteristic measuring device comprising: The fourth opening has a different shape from the three openings.
The acoustic characteristic measuring apparatus according to claim 1. The direction in which the extension tube extends is different from the direction in which the acoustic tube extends,
The acoustic characteristic measuring device according to claim 1. The extension tube has flexibility,
The acoustic characteristic measuring device according to any one of claims 1 to 3. The acoustic characteristic sensor is a sensor that measures acoustic impedance at different positions in a plane perpendicular to an axis in a direction in which the acoustic tube extends,
An acoustic characteristic acquisition means for acquiring a representative value based on the acoustic impedance at each position measured in a state where a measurement target is attached to the fourth opening, and acquiring a sound absorption characteristic based on the representative value;
The acoustic characteristic measuring device according to any one of claims 1 to 4. The acoustic characteristic sensor is a sensor that measures acoustic intensity,
It said fourth respective sound intensity was measured in a state fitted with respective to the opening and the measurement object substantially complete sound absorber with substantially complete reflector I, I _A, when the I _R, the reflectance r = comprises (I _a -I) / acoustic characteristic obtaining means for obtaining a sound-absorbing characteristics corresponding to (I _a -I _R),
The acoustic characteristic measuring device according to any one of claims 1 to 4. The acoustic characteristic sensor is a sensor that measures acoustic intensity,
Reflectance r = (I _A −I) / I where I and I _A are the acoustic intensities measured with the measurement target and the substantially perfect sound absorber attached to the fourth opening. Comprising an acoustic characteristic acquisition means for acquiring a sound absorption characteristic corresponding to _A ;
The acoustic characteristic measuring device according to any one of claims 1 to 4. The acoustic characteristic sensor includes a first microphone and a second microphone closer to the fourth opening than the first microphone,
A transfer function from the position of the first microphone to the position of the second microphone is acquired based on output signals of the first microphone and the second microphone measured with the measurement target attached to the fourth opening. An acoustic characteristic acquisition means for acquiring a sound absorption characteristic based on the transfer function, a distance from the first microphone to the second microphone, and a distance from the measurement object to the first microphone;
The acoustic characteristic measuring device according to any one of claims 1 to 4. An acoustic tube capable of exciting a measurement sound consisting of a plane wave inside by communicating with a substantially the same diameter from the first opening to the second opening;
The third opening that can be attached to and detached from the second opening is communicated from the fourth opening to the fourth opening, and the traveling direction of the measurement sound is set between the third opening and the fourth opening in the acoustic tube. An extension tube for guiding the measurement sound in a direction different from the traveling direction of the measurement sound,
An acoustic characteristic measuring device comprising: With respect to the second opening of the acoustic tube that communicates with the substantially same diameter from the first opening to the second opening, the third opening that can be attached to and detached from the second opening communicates with the fourth opening. By attaching an extension tube, the traveling direction of the measurement sound is guided between the third opening and the fourth opening in a direction different from the traveling direction of the measurement sound in the acoustic tube, and the first opening A measurement sound is output into the acoustic tube by a speaker connected to the unit, and an acoustic characteristic of the measurement sound in the acoustic tube is measured;
Acoustic characteristic measurement method.

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