JP2017053709A - Acoustic tube, and device, method and program for acoustic characteristic measurement using acoustic tube, and recording medium recording program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure a sound production characteristic specific to a soundproof material, i.e. a sound insulation characteristic combining sound via a path about which vibration of a board is transmitted to the soundproof material which in turn radiates sound, and sound via a path about which sound output inside by the vibration of the board passes through the soundproof material, and to measure the sound production characteristic and a sound absorption characteristic of the soundproof material at the same time using the same test piece.SOLUTION: An acoustic tube comprises: a tube body; a first holding member that is provided at one end of the tube body via an elastic member, and holds a test piece; a sound source unit that is provided at the other end of the tube body and produces a sound wave toward the test piece held by the first holding member; a plurality of sound pressure measuring units that include sound pressure measuring units provided at a prescribed distance interval in the tube axis direction of the tube body; and a force measuring unit that measures force received by the first holding member when the sound source unit produces the sound wave.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an acoustic tube and an apparatus, method, program, and recording medium for recording the program for measuring acoustic characteristics using the acoustic tube.

  Various acoustic characteristic measurement methods have been proposed for the design of soundproof materials and soundproof structures.

  The acoustic characteristic measurement method disclosed in Non-Patent Document 1 uses an acoustic tube as shown in FIG. A sound absorbing material test body holder 82 for holding a sound absorbing material test body 91 is provided at one end of the tube main body 80 of the acoustic tube 8, and a sound absorbing material test body 91 held by the sound absorbing material test body holder 82 at the other end. A speaker 83 for generating sound waves toward is provided. Two microphones 84 and 85 are provided on the tube wall of the tube body 80 at a predetermined distance in the tube axis direction. A complex sound pressure transfer function between two points is obtained from the sound pressure measured by each of the microphones 84 and 85, and an incident wave and a reflected wave to the specimen 91 of the sound absorbing material are calculated from the complex sound pressure transfer function. It is used to calculate the sound absorption coefficient and acoustic impedance of a sound absorbing material and is widely known.

  The acoustic characteristic measurement method disclosed in Japanese Patent Laid-Open No. 2002-54988 (Patent Document 1) uses an acoustic tube as shown in FIG. 12, and the acoustic characteristic measurement method disclosed in Non-Patent Document 1 above. Is developed so that transmission characteristics can be measured. 12, parts corresponding to those in FIG. 11 are denoted by the same reference numerals, and redundant description is omitted. A sound insulation material test body holder 88 for detachably holding a sound insulation material test body 92 is provided at the center of the tube body 80, and between the sound insulation material test body holder 88 and the speaker 83, Two microphones 86 and 87 are further provided on the tube wall at a predetermined distance in the tube axis direction. Based on the sound pressure measured by each of the microphones 86, 87, an incident wave to the sound insulation material test body 92 is calculated, and based on the sound pressure measured by each of the microphones 84, 85, the sound insulation material test body 92 is calculated. The transmitted wave that has passed through is calculated. The transmission characteristic (vertical transmission loss) of the sound insulating material is calculated from the incident wave and the transmitted wave of the sound insulating material to the test body 92 calculated. The sound absorption rate of the sound absorbing material is the same as in the acoustic characteristic measuring method disclosed in Non-Patent Document 1 above, and the incident wave and the reflection of the sound absorbing material on the specimen 91 from the sound pressure measured by each of the microphones 84 and 85. Waves are calculated and determined.

  The acoustic characteristic measurement method disclosed in Japanese Patent Application Laid-Open No. 7-27747 (Patent Document 2) is a ratio of the mechanical power applied to the soundproof material (excitation power) and the acoustic power radiated into the air thereby. The acoustic radiation efficiency is obtained based on the sound pressure of the sound radiated from the sound source, the displacement due to the vibration of the measured object caused by the sound radiated from the sound source, and the physical property value of the measured object.

JP 2002-54988 A JP-A-7-27747

Japan Industrial Standards Committee, “Measurement of sound absorption coefficient and impedance by acoustic tube”-Part 2: Transfer function method JIS A 1405-2: 2007

  However, in the design of conventional sound insulation materials and sound insulation structures, the elements of the sound insulation characteristics are the sound transmitted through the sound insulation material and the vibration of the wall surface (hereinafter also referred to as “plate” for simplicity) transmitted to the sound insulation material. The soundproofing material itself can be decomposed into sound radiated by vibration, both of which need to be considered, so the soundproofing characteristics cannot be considered by the soundproofing material alone, the soundproofing material and the soundproofing The need to think about the system of plates with the material attached was not recognized.

  Further, the conventional acoustic characteristic measuring apparatus cannot measure the sound insulation characteristic unique to the sound insulation material, that is, the sound insulation characteristic of the sound insulation material alone attached to a rigid plate in a vacuum. Here, many of the soundproofing materials have many air gaps, but such a soundproofing material greatly affects soundproofing by air filling the air gaps as described later. The sound insulation characteristic in vacuum is a sound insulation characteristic when it is assumed that the outside of the soundproof material is vacuum and the air gap inside the soundproof material is filled with air. Therefore, even if it is going to measure the acoustic characteristic of a soundproof material under vacuum using the conventional acoustic characteristic measuring apparatus, the space | gap part of a soundproof material collapses under vacuum and an original acoustic characteristic cannot be measured. Hereinafter, the above problem will be described in detail.

  First, the mechanism of sound insulation is examined. In many cases, the soundproofing material is not used alone as in the case of gypsum board, but is used with a soundproofing material attached to the wall surface. In the case of a soundproof structure in which a soundproof material is pasted on a wall surface, it can be broken down into vibration suppression by the wall surface, sound insulation by the soundproof material, and sound absorption by the soundproof material as elements for achieving soundproofing (see FIG. 1).

  Among these, as for the sound absorption by the soundproofing material, the sound absorption characteristic (vertical incident sound absorption coefficient) can be measured by the method as shown in Non-Patent Document 1 as described above.

  On the other hand, the vibration control by the wall surface and the sound insulation by the soundproofing material have been conventionally measured as the sound insulation characteristics of the entire soundproof structure. That is, the sound insulation characteristic which combined the characteristic of the board and the characteristic of the soundproofing material was measured about what put the soundproofing material on the board assumed the actual structure.

  When the mechanism of sound insulation is further examined, referring to FIG. 2A, the sound outside the soundproof structure is once converted into vibration of the plate and transmitted to the inside. Here, a considerable degree of sound insulation is provided by the vibration damping effect of the plate itself. The sound due to the vibration of the plate propagates in two paths. One path is a path (path 1) through which the vibration of the plate is transmitted to the soundproofing material and the soundproofing material emits sound, and the other path is a sound that is emitted inside by the vibration of the plate and passes through the soundproofing material. Route (route 2) to be performed.

  Among these, with respect to the sound transmitted through the soundproofing material due to the vibration of the plate of the path 2, the transmission characteristic (vertical incident transmission loss) is obtained by using the technique shown in the above-mentioned Patent Document 1. Can be measured. However, as shown in FIG. 2 (b), this transmission characteristic is a characteristic of the soundproofing material not attached to the plate, and the path 2 (the sound emitted inside by the vibration of the plate passes through the soundproofing material). This is different from the characteristics of the route to be performed. Moreover, in the technique as shown in the above-mentioned patent document 1, the sound radiated when the vibration of the plate of the path 1 is transmitted to the soundproof material and the soundproof material itself vibrates is not taken into consideration. Therefore, the sound passes through the route 1 (the route through which the vibration of the plate is transmitted to the soundproofing material and the soundproofing material emits sound) and the route 2 (the route through which the sound emitted by the vibration of the plate passes through the soundproofing material). The sound insulation characteristic combined with the sound cannot be measured by the method as disclosed in Patent Document 1 described above.

  In this respect, in the method shown in the above-mentioned Patent Document 1, not only the soundproof material but the soundproof material affixed to the plate is used as the test material, the sound via the route 1 and the sound via the route 2 are used. It is not possible to measure the sound insulation characteristics combined with Hereinafter, the reason will be described by taking a carpet, which is the most common soundproofing material in an automobile, as an example.

  As shown in the diagram on the left side of FIG. 3, the carpet is composed of a sound absorbing material and rubber. The principle of the soundproof structure composed of a plate and a carpet attached to the plate can be described using a mass-spring model, as shown in the diagram on the right side of FIG. That is, it can be seen that rubber and sound absorbing material correspond to mass M and spring (spring constant K), respectively, and even if the plate vibrates, the vibration is suppressed on the carpet surface.

  Here, since the sound absorbing material has many air gaps and the air gaps are filled with air, it should be noted that the air in the sound absorbing material has a greater influence on the spring constant K than the hardness of the sound absorbing material. That is, the smaller the thickness of the sound absorbing material, which is the thickness of the air layer, the harder the spring, and at the normal carpet thickness, the rigidity of the sound absorbing material itself is 1/3 or less of the rigidity of the air layer. .

  In the method as shown in Patent Document 1 above, when measuring a test piece of carpet alone, as shown in FIG. 4A, there is no plate, so the sound from the sound source passes through the gap in the sound absorbing material. As a result, the spring is not reproduced, and the transmission characteristics of rubber that is substantially a mass are measured.

  On the other hand, if a test body with a carpet attached to a plate is measured, as shown in FIG. 4B, the spring is reproduced, but the transmission characteristics of the plate are substantially measured.

  Therefore, in any case, with the technique shown in the above-mentioned Patent Document 1, it is impossible to measure the sound insulation characteristics of the sound through the route 1 of the carpet and the sound through the route 2.

  Further, with the technique as disclosed in Patent Document 1, it is not possible to simultaneously measure the sound absorption characteristic and the transmission characteristic for the same specimen. That is, in order to measure the sound absorption characteristic and the transmission characteristic for the same specimen, first, the specimen is attached to the sound absorbing material specimen holder 82 and the sound absorbing characteristics are measured. Must be removed and attached to the sound insulation specimen holder 88 to measure the transmission characteristics, or vice versa. If different test specimens are used for the same soundproofing material, the sound absorption characteristics and the transmission characteristics can be measured simultaneously, but the measurement results vary because the test specimens are different.

  The method described in Patent Document 2 is to measure the ratio of the acoustic radiation efficiency, that is, the mechanical power applied to the soundproofing material (vibration power) and the acoustic power radiated into the air by this, It can be said that the sound insulation characteristic combining the sound via route 1 and the sound via route 2 is measured.

  However, the radiated acoustic power is greatly influenced by the sample shape of the soundproof material and the characteristics of the space around the soundproof material sample (for example, the magnitude of noise in the surrounding space). Therefore, the acoustic radiation efficiency measured by the method described in Patent Document 2 is meaningful only under the measurement conditions (the sample shape of the soundproof material and the characteristics of the space around the soundproof material sample). With the technique described in Patent Document 2, it is not possible to measure the sound insulation characteristic unique to the soundproofing material that does not depend on the measurement conditions.

  Further, as described above, the radiated sound power is affected by the noise level in the space around the soundproofing material sample, so it is necessary to perform measurement in an anechoic chamber.

  Therefore, the present invention provides a sound generation characteristic unique to the soundproofing material, that is, the sound passing through the above-described path 1 (path where the vibration of the plate is transmitted to the soundproofing material and the soundproofing material emits sound) and the path 2 (inside by vibration of the board). One of the purposes is to measure the sound insulation characteristics by combining the sound that passes through the soundproofing material through the sound.

  Another object of the present invention is to simultaneously measure the sound generation characteristics and sound absorption characteristics of a soundproofing material with the same specimen.

  One aspect of the present invention is provided in a tube main body, a first holding member that is provided at one end portion of the tube main body via an elastic member, and a second end portion of the tube main body. In addition, a sound source unit that generates a sound wave toward the test body held by the first holding member, and a sound pressure measurement unit provided at intervals of a predetermined distance in the tube axis direction of the tube main body, An acoustic tube is provided that includes a plurality of sound pressure measurement units and a force measurement unit that measures a force received by the first holding member when the sound source unit generates the sound wave.

  The acoustic tube may further include a second holding member that holds the force measuring unit and is connected to the one end of the tube main body.

  The plurality of sound pressure measuring units are three or more sound pressure measuring units, and the acoustic tube is a third holding member for disposing at least one sound pressure measuring unit in the vicinity of the surface of the specimen. Can be further provided.

  One aspect of the present invention is to calculate the sound generation characteristics of the specimen based on the acoustic tube, sound pressure information measured by the plurality of sound pressure measurement units, and force information measured by the force measurement unit. An acoustic characteristic measurement device including a sound generation characteristic calculation unit that performs the above-described process is provided.

  The acoustic characteristic measuring device calculates a sound pressure on the surface of the test body or a sound pressure near the surface of the test body based on sound pressure information measured by the plurality of sound pressure measuring sections. The sound generation characteristic calculation unit further comprises the sound pressure of the test body based on the calculated sound pressure near the surface of the test body or in the vicinity of the surface of the test body and the force information measured by the force measurement section. Characteristics can be calculated.

  The acoustic characteristic measurement device may further include a sound absorption characteristic calculation unit that calculates a sound absorption characteristic of the specimen based on sound pressure information measured by the plurality of sound pressure measurement units.

  The sound generation characteristic calculation unit and / or the sound absorption characteristic calculation unit can calculate the sound generation characteristic of the test body and / or the sound absorption characteristic of the test body with reference to an input signal to the sound source unit.

  One aspect of the present invention is a method for measuring the acoustic characteristics of the specimen using the acoustic tube, the step of acquiring sound pressure information measured by the plurality of sound pressure measuring units, and the force Based on the step of obtaining force information measured by the measurement unit, the sound pressure information measured by the plurality of sound pressure measurement units, and the force information measured by the force measurement unit, And a step of calculating.

  The method for measuring the acoustic characteristics of the specimen using the acoustic tube is based on sound pressure information measured by the plurality of sound pressure measuring units, and the sound near the surface of the specimen or near the surface of the specimen. A step of calculating or acquiring a pressure, and based on the calculated sound pressure near the surface of the test body or the surface of the test body and force information measured by the force measuring unit. Pronunciation characteristics can be calculated.

  The method of measuring the acoustic characteristics of the specimen using the acoustic tube further includes a step of calculating the sound absorption characteristics of the specimen based on sound pressure information measured by the plurality of sound pressure measuring units. Can do.

  The step of calculating the sound generation characteristic of the test body and / or the step of calculating the sound absorption characteristic of the test body may be performed with reference to an input signal to the sound source unit.

  One aspect of the present invention provides a program for causing a computer to execute a method for measuring the acoustic characteristics of the specimen using the acoustic tube.

  One aspect of the present invention provides a computer-readable recording medium in which the program is recorded.

  According to the present invention having the above-described configuration, the sound generation characteristic peculiar to the soundproof material, that is, the sound and the route 2 (board) through the above-described path 1 (path through which the vibration of the plate is transmitted to the soundproofing material and the soundproofing material emits sound). The sound insulation characteristics can be measured by combining the sound that has passed through the soundproofing material through the sound emitted inside due to the vibration of the sound. And, by making it possible to measure the sound generation characteristics unique to the soundproofing material, it is not necessary to measure the sound insulation characteristics with a soundproofing material pasted on a plate that assumes an actual structure as in the past. It opens the way to simulate the sound insulation characteristics in

  Further, according to the present invention having the above-described configuration, the sound generation characteristic and the sound absorption characteristic of the soundproofing material can be measured simultaneously with the same specimen, and the measurement time is shortened and the measurement variation is reduced.

It is a figure which shows the mechanism of soundproofing. It is a figure which shows the mechanism of sound insulation. It is a figure which shows the soundproof structure using the carpet which is an example of a soundproof material, and its mass-spring model. (A) is a figure which shows the case where the test piece of a carpet alone is measured using a mass-spring model in the technique as shown in patent document 1, and (b) is shown in patent document 1. It is a figure which shows the case where the test body which stuck the carpet on the board is measured using a mass-spring model in a simple technique. 1 is an overall configuration diagram of an acoustic characteristic measurement device according to one embodiment of the present invention. (A) And (b) is a figure which shows the simulation model which confirms establishment of the reciprocity of a structure and an acoustic. It is a figure which shows the result of the simulation which confirms establishment of reciprocity of a structure and an acoustic. It is a flowchart of the acoustic characteristic measurement process of the acoustic characteristic measuring apparatus which concerns on one Embodiment of this invention. It is a figure which shows the case where a test body is measured using the acoustic tube which concerns on one Embodiment of this invention using a mass-spring model. It is a whole block diagram of the acoustic characteristic measuring apparatus which concerns on another embodiment of this invention. It is a figure which shows one example of the conventional acoustic tube. It is a figure which shows another example of the conventional acoustic tube.

Embodiments of the present invention will be described below with reference to the drawings.
(First embodiment)
FIG. 5 is an overall configuration diagram of the acoustic characteristic measuring apparatus according to the first embodiment of the present invention.

  As shown in FIG. 5, the acoustic characteristic measurement device 1 according to the present embodiment includes an acoustic tube 2, a calculation device 3, and a speaker amplifier 4.

  The acoustic tube 2 includes a tube main body 20, an elastic member 21, a first holding member 22, a speaker 23 as a sound source unit, microphones 24 and 25 as a sound pressure measurement unit, a load washer 27 as a force measurement unit, a second A holding member 28 is provided.

  The tube main body 20 is a cylindrical straight tube (straight tube) that is formed of metal, plastic, or the like, or whose inner wall surface is coated to ensure airtightness. One end portion of the tube body 20 has a flange portion 201 that extends radially outward. The shape of the cross section of the tube body 20 may be any shape such as a square.

  The first holding member 22 is provided at one end of the tube body 20 via the elastic member 21 and holds the test body 5 of the soundproof material. The first holding member 22 is made of aluminum, which is a lightweight and highly rigid metal for reasons described later. Further, as described later, the elastic member 21 has a resonance frequency such that the first holding member 22 can be regarded as receiving no force from the direction of the speaker 23 other than the sound pressure. The one is selected.

  The speaker 23 which is a sound source unit is provided at the other end of the tube body 20 and generates sound waves toward the test body 5 held by the first holding member 22. The sound source unit is not limited to the speaker, and may be any other appropriate sound source.

  The microphones 24 and 25 that are sound pressure measuring units are provided on the tube wall of the tube body 20 at a predetermined interval in the tube axis direction, and measure the sound pressure generated in the tube body 20 at each installation position. The sound pressure measurement unit is not limited to the microphone, and may be any other appropriate sound pressure sensor.

  The second holding member 28 includes a disc-shaped main body 281, a cylindrical portion 282, a first flange portion 283, a second flange portion 284, a first recess 285, and a second recess 286. The cylindrical portion 282 is provided on the outer edge portion of the main body portion 281 so as to extend toward the speaker 23. Further, the end portion of the cylindrical portion 282 on the speaker 23 side has a first flange portion 283 extending outward in the radial direction. The load washer 27 is placed on the surface of the main body 281 facing the speaker 23, and the first holding member 22 is placed on the surface of the load washer 27 facing the speaker 23. As described above, since the elastic member 21 is disposed between the first holding member 22 and one end of the tube main body 20, the first holding member 22 moves according to the movement of the test body 5. The first holding member 22 receives a force equal to the force that the test body 5 receives from the sound pressure generated in the tube main body 20. The load washer 27 and the first holding member 22 are accommodated in a first recess 285 formed by a main body portion 281 and a cylindrical portion 282. The first flange portion 283 and the flange portion 201 of the pipe body 20 are connected by a bolt. The second flange portion 284 extends from the outer edge portion of the main body portion 281 opposite to the speaker 23 toward the radially outer side, and is fixed to the surface plate 6 by bolts 287. In addition, a second recess 286 is provided on the surface plate 6 side of the main body 281, and a fixing bolt 288 is inserted through a hole penetrating the center of the main body 281 and the load washer 27, so that the first holding member 22 The first holding member 22, the load washer 27, and the second holding member 28 are coupled by being screwed into a female screw portion provided on the side opposite to the speaker 23. The second holding member 28 is made of highly rigid iron for the reasons described later. The shape of the second holding member is not limited to the above shape, and may be any other appropriate shape.

  Here, the natural frequency of the combined body of the first holding member 22, the load washer 27, and the second holding member 28 is such that the combined body can be regarded as a rigid plate with respect to the test body 5. In order to do this, it is necessary to make it higher than the upper limit frequency of the measurement target. In the present embodiment, the resonance frequency when the load washer 27 and the second holding member 28 are springs and the first holding member 22 is a mass may be low, so the first holding member 22 is light in weight. The rigidity of the specimen 5 is ensured by using aluminum which is a highly rigid metal and using iron which is a highly rigid metal for the second holding member 28. The material of the first holding member 22 is not limited to aluminum, and may be any other appropriate material (for example, duralumin) that is lightweight and has high rigidity. Further, the material of the second holding member 28 is not limited to iron, and may be any other appropriate material (for example, stainless steel) having high rigidity. Here, since the second holding member does not need to be light, iron or stainless steel having a large weight can be used as the material of the second holding member. Further, the elastic member 21 disposed between the one end portion of the tube body 20 and the first holding member 22 has a resonance frequency in which the first holding member 22 has a force from the direction of the speaker 23 in addition to the sound pressure. The frequency is selected such that it can be regarded as not being received. When measuring high frequency characteristics, a small diameter acoustic tube may be used.

  In such a configuration, when the test body 5 is vibrated by the sound pressure generated in the tube main body 20, as described above, the first holding member 22 exerts a force from the direction on the speaker 23 side in addition to the sound pressure. Therefore, the first holding member 22 receives a force fr equal to the force that the test body 5 receives from the sound pressure generated in the tube main body 20. A force fr is applied to the load washer 27, and the force fr is measured by the load washer 27. On the other hand, since the combined body of the first holding member 22, the load washer 27, and the second holding member 28 can be regarded as a rigid plate with respect to the test body 5 as described above, the first holding member 22 receives a force equal in magnitude to fr from the load washer 27 as a reaction force. Therefore, the magnitude of the force fr is equal to the magnitude of the reaction force that the first holding member 22 receives from the load washer 27. The force information of the force fr measured by the load washer 27 is acquired by a force acquisition unit 34 described later.

  With such a configuration, the load washer 27 serving as a force measuring unit receives the force received by the first holding member 22 when the speaker 23 generates sound waves (the force received from the test body 5 = the reaction force from the load washer 27). ) Can be measured. The force measuring unit is not limited to a load washer, and may be any other appropriate force sensor.

  The computing device 3 is a computer device having a CPU, a communication function, a storage function (drive unit and / or input / output interface for an internal recording medium and an external recording medium), an input function (keyboard, mouse, etc.), and a display function (display). And a predetermined computer program. The computer program includes a sound wave signal generation unit 31, an input signal acquisition unit 32, a sound pressure acquisition unit 33, a force acquisition unit 34, a specimen surface sound pressure calculation unit 35, a sound generation characteristic calculation unit 36, and a sound absorption characteristic calculation. It functions as the unit 37.

  The sound wave signal generation unit 31 generates a sound wave signal to be reproduced by the speaker 23 as a sound source.

  The input signal acquisition unit 32 acquires a signal input to the speaker 23, that is, a sound wave signal generated by the sound wave signal generation unit 31 and amplified by the speaker amplifier 4.

  The sound pressure acquisition unit 33 acquires sound pressure information of the sound pressure generated in the tube main body 20 at each installation position, measured by the microphones 24 and 25.

  The force acquisition unit 34 acquires force information measured by the load washer 27.

The test body surface sound pressure calculation unit 35 calculates the sound pressure p ₀ on the surface of the test body 5 or in the vicinity of the surface of the test body 5 based on the sound pressure information acquired by the sound pressure acquisition unit 33. Since this calculation method is well known as shown in, for example, Non-Patent Document 1 above, detailed description thereof is omitted.

The sound generation characteristic calculator 36 calculates the sound generation characteristic of the test body 5 based on the sound pressure information measured by the microphones 24 and 25 and the force information measured by the load washer 27. In the present embodiment, the sound generation characteristic calculation unit 36 is acquired by the force acquisition unit 34 and the sound pressure p ₀ near the surface of the test body 5 or near the surface of the test body 5 calculated by the test body surface sound pressure calculation unit 35. Based on the reaction force fr received by the first holding member 22, the sound generation characteristic of the test body 5 is calculated.

Here, the sound generation characteristics are the sound through the path 1 (path through which the vibration of the plate is transmitted to the soundproofing material and the soundproofing material radiates sound) and the sound of the path 2 (the sound emitted inside by the vibration of the plate). This is the sound insulation characteristic that combines the sound that passes through the material. Therefore, when the acceleration of air on the surface of the test body or in the vicinity of the surface of the test body when the member holding the test body is vibrated at a constant acceleration a ₀ , the sound generation characteristic can be expressed as a / a ₀ . For the sound generation characteristic a / a ₀ , the reaction force received by the member holding the test body in the state of being vibrated by the speaker is fr, and the sound on the surface of the test body in the state of being vibrated by the speaker or in the vicinity of the surface of the test body When the pressure is p ₀ and the cross-sectional area of the acoustic tube is S, due to the reciprocity between the structure and the sound,
| A / a ₀ | = | fr / Sp ₀ | (1)
Is established. Therefore, the sound generation characteristic a / a ₀ can be calculated from the equation (1) based on the acquired sound pressure p ₀ , reaction force fr, and cross-sectional area S of the acoustic tube.

  Here, the result of the simulation for confirming that the reciprocity between the structure represented by the formula (1) and the sound is established for the acoustic tube of the above embodiment will be described.

A finite element model as shown in FIG. 6A was created for the acoustic tube of the above embodiment, and simulation was performed using the software ACTRAN from MSC. The inside of the tube main body 20 is filled with air, the speaker 23 is a point sound source 23 ′, the test body 5 is a foam type sound absorbing material of melamine resin, and a Biot parameter measured in advance is given to the sound absorbing material. Moreover, in the said embodiment, although the aluminum 1st holding member 22 couple | bonded with the load washer 27 and the iron 2nd holding member 28 was used as a rigid board to which the test body 5 is affixed, this book In the simulation, a rigid plate to which the test body 5 is attached is a single iron plate. The distance from the point sound source 23 ′ to the surface of the iron plate 22 ′ facing the test body 5 is 500 mm, the diameter of the tube body 20 is 100 mm, the test body 5 has a disk shape, the diameter is 100 mm, and the thickness is 50 mm. . Under such conditions, the value of | fr / Sp ₀ | was simulated.

On the other hand, for the structure of only the same rigid plate and foam type sound absorbing material as described above, the value of | a / a ₀ | with respect to the acceleration a of the sound absorbing material when the rigid plate is vibrated at a constant acceleration a ₀ is A finite element model as shown in FIG. 6B was created and similarly simulated.

FIG. 7 shows the simulation result. The solid line is the value of | fr / Sp ₀ |, and the dotted line is the value of | a / a ₀ |. Both are in agreement, and the characteristic a / a ₀ of the soundproofing material can be measured from the value obtained by dividing the reaction force fr of the soundproofing material by the product of the sound pressure p _{0 on the} surface of the sound absorbing material and the cross-sectional area S of the sound pipe. I understand that there is.

  The sound absorption characteristic calculation unit 37 calculates the sound absorption characteristic of the test body 5 based on the sound pressure information of the sound pressure measured by the microphones 24 and 25 acquired by the sound pressure acquisition unit 33. Since this calculation method is well known as shown in, for example, Non-Patent Document 1 above, detailed description thereof is omitted.

  Based on the above apparatus configuration, an example of the acoustic characteristic measurement process of the acoustic characteristic measuring apparatus according to the embodiment of the present invention will be described below with reference to FIG.

  First, the sound wave signal generation unit 31 generates a sound wave signal to be reproduced as a sound source by the speaker 23 (S1).

  The generated sound wave signal is amplified by the speaker amplifier 4 and input to the speaker 23. The speaker 23 converts the amplified sound wave signal into sound waves, and generates sound waves toward the test body 5 held by the first holding member provided at one end of the tube body 20 (S2).

  The microphones 24 and 25 measure the sound pressure generated in the tube main body 20 by the sound wave generated by the speaker 23, and the sound pressure information of the measured sound pressure is acquired by the sound pressure acquisition unit 33 (S3).

  The load washer 27 measures the force fr received by the first holding member 22, and the force information of the measured force fr is acquired by the force acquisition unit 34 (S4).

The test body surface sound pressure calculation unit 35 calculates the sound pressure p ₀ near the surface of the test body 5 or near the surface of the test body 5 based on the sound pressure information acquired by the sound pressure acquisition unit 33 (S5).

The sound generation characteristic calculation unit 36 includes the sound pressure p ₀ calculated by the test body surface sound pressure calculation unit 35 or the sound pressure p ₀ near the surface of the test body 5 and the first holding acquired by the force acquisition unit 34. Based on the force fr received by the member 22, the sound generation characteristic of the test body 5 is calculated (S6).

  The sound absorption characteristic calculation unit 37 calculates the sound absorption characteristic based on the sound pressure information of the sound pressure measured by the microphones 24 and 25 acquired by the sound pressure acquisition unit 33 (S7).

  Here, the calculation of the sound generation characteristic and the calculation of the sound absorption characteristic may be performed first, or may be performed in parallel at the same time.

  In calculating the sound pressure, sound generation characteristics, and sound absorption characteristics near the surface of the test body 5 or near the surface of the test body 5, the microphones 24 and 25 are referred to by referring to the sound wave signals amplified by the speaker amplifier 4 input to the speaker 23. It is possible to eliminate the influence of external noise such as noise mixed in the measurement. As a result, it is possible to calculate more accurate pronunciation characteristics and sound absorption characteristics.

According to the configuration of the present embodiment, the following effects can be obtained.
(1) From the sound pressure measured with the microphone and the force measured with the load washer, it is possible to measure the sound generation characteristic specific to the soundproofing material with high accuracy.
(2) It is possible to simultaneously measure sound generation characteristics and sound absorption characteristics.
(3) Since the sound generation characteristic and the sound absorption characteristic can be measured simultaneously with the same specimen, the measurement time can be shortened and the measurement variation can be reduced.
(4) In the present embodiment, the spring model described above with reference to FIG. 4 is as shown in FIG. 9, and the plate is fixed and does not vibrate. It is possible to reproduce the spring without giving it.
(5) Since measurement is performed in a closed space, it is not necessary to perform measurement in an anechoic chamber, and it is difficult to be influenced by surrounding noise, so that highly accurate measurement is possible.
(6) Since a structure without moving parts is adopted, it is possible to avoid a decrease in measurement accuracy due to rattling or the like.

(Second Embodiment)
FIG. 10 is an overall configuration diagram of an acoustic characteristic measuring apparatus according to the second embodiment of the present invention. With reference to FIG. 10, the configuration and operation principle of the second embodiment of the present invention will be described. 10, parts corresponding to those in FIG. 5 are denoted by the same reference numerals, and description overlapping with the first embodiment is omitted.

  In the present embodiment, the difference from the first embodiment is that, in addition to the microphones 24 and 25, a microphone holder 29, which is a third holding member for arranging the microphone 26 in the vicinity of the surface of the test body 5, is connected to the tube. This is a point provided on the tube wall of the main body 20. The sound pressure information of the sound pressure near the surface of the test body 5 measured by the microphone 26 is acquired by the sound pressure acquisition unit 33.

According to the present embodiment, in the first embodiment, the sound pressure p ₀ near the surface of the test body 5 or near the surface obtained by calculation from the sound pressure measured by the microphones 24 and 25 is directly measured. Therefore, it becomes possible to measure the pronunciation characteristics with higher accuracy.

  Although the present invention has been described above with reference to several embodiments for purposes of illustration, the present invention is not limited thereto, and forms and details are within the scope and spirit of the present invention. It will be apparent to those skilled in the art that various modifications and variations can be made.

DESCRIPTION OF SYMBOLS 1 Acoustic characteristic measuring apparatus 2 Acoustic tube 20 Tube main body 201 Flange part 21 Elastic member 22 1st holding member 22 'Iron plate 23 Speaker 23' Point sound source 24 Microphone 25 Microphone 26 Microphone 27 Load washer 28 2nd holding member 281 Main body part 282 Cylindrical portion 283 First flange portion 284 Second flange portion 285 First concave portion 286 Second concave portion 287 Bolt 288 Fixing bolt 29 Microphone holder 3 Arithmetic device 31 Sound wave signal generation portion 32 Input signal acquisition portion 33 Sound pressure acquisition Unit 34 Force acquisition unit 35 Test body surface sound pressure calculation unit 36 Sound generation characteristic calculation unit 37 Sound absorption characteristic calculation unit 4 Speaker amplifier 5 Test body 6 Surface plate 8 Acoustic tube 80 Tube body 82 Sound absorption material test body holder 83 Speaker 84 Microphone 85 Microphone 86 Microphone 87 Microphone 88 Sound insulation material specimen DA 91 Sound-absorbing material specimen 92 Sound-insulating material specimen

Claims (11)

A tube body;
A first holding member for holding a test body, provided at one end of the tube body via an elastic member;
A sound source section that is provided at the other end of the tube main body and generates a sound wave toward the test body held by the first holding member;
A plurality of sound pressure measurement units including a sound pressure measurement unit provided at intervals of a predetermined distance in the tube axis direction of the tube body;
A force measuring unit that measures a force received by the first holding member when the sound source unit generates the sound wave;
An acoustic tube.   The acoustic tube according to claim 1, further comprising a second holding member connected to the one end of the tube main body and holding the force measuring unit.   The plurality of sound pressure measurement units is three or more sound pressure measurement units, and further includes a third holding member for disposing at least one sound pressure measurement unit in the vicinity of the surface of the specimen. The acoustic tube according to 1 or 2. The acoustic tube according to any one of claims 1 to 3,
A sounding characteristic calculation unit that calculates sounding characteristics of the specimen based on sound pressure information measured by the plurality of sound pressure measuring units and force information measured by the force measuring unit;
An acoustic characteristic measuring device comprising:   The acoustic characteristic measurement device according to claim 4, further comprising a sound absorption characteristic calculation unit that calculates a sound absorption characteristic of the specimen based on sound pressure information measured by the plurality of sound pressure measurement units.   The sound generation characteristic calculation unit and / or the sound absorption characteristic calculation unit refers to an input signal to the sound source unit, and calculates the sound generation characteristic of the test body and / or the sound absorption characteristic of the test body. Acoustic characteristic measuring device. A method for measuring acoustic characteristics of the specimen using the acoustic tube according to any one of claims 1 to 3,
Obtaining sound pressure information measured by the plurality of sound pressure measuring units;
Obtaining force information measured by the force measuring unit;
Calculating sound generation characteristics of the specimen based on sound pressure information measured by the plurality of sound pressure measuring units and force information measured by the force measuring unit;
Including methods.   The method according to claim 7, further comprising calculating a sound absorption characteristic of the specimen based on sound pressure information measured by the plurality of sound pressure measuring units.   The method according to claim 7 or 8, wherein the step of calculating the sound generation characteristic of the test body and / or the step of calculating the sound absorption characteristic of the test body is performed with reference to an input signal to the sound source unit.   The program for making a computer perform the method of any one of Claims 7-9.   The computer-readable recording medium which recorded the program of Claim 10.

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