Density determination device and method

Abstract

To provide a density determination device and method that can improve density measurement performance.SOLUTION: A density determination device of an embodiment comprises a container 11, a sound wave generation unit 12, a sound wave measurement unit 13, a resonance frequency calculation unit 20, a reverberation characteristic calculation unit 30, and a density determination unit 40. An object 14 can be installed in the container 11. The sound wave generation unit 12 generates sound waves inside the container 11. The sound wave measurement unit 13 measures the sound waves inside the container 11 and outputs sound wave information A1, and measures reverberation inside the container 11 and outputs sound wave information A2. The resonance frequency calculation unit 20 calculates the resonance frequency of resonance generated inside the container 11 by using the sound wave information A1. The reverberation characteristic calculation unit 30 calculates a reverberation parameter related to reverberation by using the sound wave information A2. The density determination unit 40 determines the density of the object 14 on the basis of the resonance frequency and the reverberation parameter.SELECTED DRAWING: Figure 14

Description

[Technical Field]

[0001] FIELD OF THE INVENTION An embodiment of the present invention relates to a density determination apparatus and method. [Background technology]

[0002] There are several methods for measuring the density of a substance, including submerging the object in liquid and determining its density from the buoyancy acting on it; submerging the object in liquid, measuring its volume from the overflowing water, then measuring its mass, and then determining its density from the measured volume and mass; and finally measuring the density of the object using the pressure difference caused by pressurizing and depressurizing the sample chamber in which the object is placed.

[0003] However, methods that involve submerging the measurement target in liquid are not possible for materials that are permeable or absorbent, as opposed to materials whose exteriors are covered with a water-repellent material. Furthermore, methods that apply pressure changes to the measurement target may cause deformation due to pressure changes if the measurement target is soft or has an internal cavity. Furthermore, for products where the softness and pleasant feel ensured by the delicate internal cavity are important values, this method may diminish the product's value. Therefore, when measuring the density of a material, a measurement method that does not cause changes in the shape or deterioration of the measurement target is desirable. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4911460 specification [Patent Document 2] Patent No. 6727152 specification [Patent Document 3] Japanese Patent Publication No. 2022-133713 Summary of the Invention [Problem to be solved by the invention]

[0005] A density determination device and method capable of improving density measurement performance are provided. [Means for solving the problem]

[0006] The density determination device of the embodiment includes a container in which an object can be placed, a sound wave generating unit that generates sound waves within the container, a sound wave measuring unit that measures the sound waves within the container and outputs first sound wave information, and measures the reverberation within the container and outputs second sound wave information, a resonance frequency calculating unit that calculates a resonance frequency of resonance occurring within the container using the first sound wave information, a reverberation characteristic calculating unit that calculates reverberation parameters related to the reverberation using the second sound wave information, and a density determination unit that determines the density of the object based on the resonance frequency and the reverberation parameters. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram illustrating a configuration of a density determination device according to an embodiment. [Figure 2] FIG. 1 is a conceptual diagram for explaining Helmholtz resonance occurring in a resonator. [Figure 3] FIG. 10 is a diagram showing frequency characteristics when an insert is installed in a resonator. [Figure 4] 1 is a conceptual diagram showing basic Helmholtz resonance and the influence of air column resonance on Helmholtz resonance. [Figure 5] FIG. 10 is a diagram showing the relationship between changes in air column resonance and changes in Helmholtz resonance. [Figure 6] FIG. 10 is a diagram showing a reverberation curve when an insert is installed inside the resonator. [Figure 7] FIG. 10 is a diagram showing a reverberation curve when no insert is installed in the resonator. [Figure 8] FIG. 10 shows reverberation curves measured by changing the type of insert placed inside the resonator. [Figure 9] FIG. 10 is a diagram showing the relationship between the density of the insert and the slope of the initial attenuation according to the embodiment. [Figure 10]FIG. 10 is a diagram showing the relationship between the density of an insert and the slope of equilibrium damping according to the embodiment. [Figure 11] FIG. 10 is a diagram showing the relationship between the density of the insert and the air column resonance frequency according to the embodiment. [Figure 12] FIG. 10 is a diagram showing the relationship between the density of the insert and the Helmholtz resonance frequency according to the embodiment. [Figure 13] FIG. 2 is a flowchart showing an outline of a density determination process in the density determination device according to the embodiment. [Figure 14] FIG. 4 is a flowchart showing a detailed flow of a density determination process in the density determination device according to the embodiment. [Figure 15] FIG. 10 is a diagram showing the arrangement of a first modified example of the acoustic wave information acquisition section according to the embodiment. [Figure 16] FIG. 10 is a diagram showing the arrangement of a second modified example of the acoustic wave information acquisition section according to the embodiment. [Figure 17] FIG. 10 is a diagram showing the arrangement of a third modified example of the acoustic wave information acquisition section according to the embodiment. [Figure 18] FIG. 10 is a diagram showing the arrangement of a fourth modified example of the acoustic wave information acquisition section according to the embodiment. [Figure 19] FIG. 10 is a diagram showing the arrangement of a fifth modified example of the acoustic wave information acquisition section according to the embodiment. [Figure 20] FIG. 2 is a diagram illustrating an example of a hardware configuration of a density determination device according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments will be described with reference to the drawings. In the following description, components having the same function and configuration will be assigned the same reference numerals. Furthermore, the embodiments shown below are merely examples of devices and methods for embodying the technical ideas of the embodiments, and do not specify the materials, shapes, structures, arrangements, etc. of the components as described below.

[0009] 1. Configuration of the embodiment The configuration of a density determining device according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing the configuration of a density determining device according to an embodiment.

[0010] The density determination device 1 includes a sound wave information acquisition unit 10, a resonance frequency calculation unit 20, a reverberation characteristic calculation unit 30, and a density determination unit 40.

[0011] The ultrasonic information acquisition unit 10 includes a resonator (or container) 11, a ultrasonic wave generation unit 12, and an ultrasonic wave measurement unit 13. The ultrasonic information acquisition unit 10 measures ultrasonic waves within the resonator 11 in which an object 14, the density of which is to be measured, is placed, and converts the measured ultrasonic waves into ultrasonic information for output. Details of the resonator 11, the ultrasonic wave generation unit 12, and the ultrasonic wave measurement unit 13 will be described later.

[0012] The resonance frequency calculation unit 20 calculates the resonance frequency using the sound wave information output from the sound wave information acquisition unit 10. The reverberation characteristics calculation unit 30 calculates the reverberation characteristics (or reverberation parameters) using the sound wave information output from the sound wave information acquisition unit 10.

[0013] The density determination unit 40 determines the density of the object 14 based on the resonance frequency calculated by the resonance frequency calculation unit 20 and the reverberation characteristics calculated by the reverberation characteristic calculation unit 30, and outputs a density determination result 2.

[0014] The resonator 11, sound wave generating unit 12, and sound wave measuring unit 13 included in the sound wave information acquiring unit 10 will be described below. The X direction, Y direction, and Z direction are directions that intersect with each other. For example, the X direction, Y direction, and Z direction are perpendicular to each other. The X direction intersects with the YZ plane.

[0015] The resonator 11 is configured by connecting two containers, a container 11a and a container 11b. That is, the container 11b is connected to one end of the container 11a in the X direction. The containers 11a and 11b have different cavity sizes. The volume of the container 11a is larger than the volume of the container 11b. In other words, the cross-sectional area of the container 11a along the YZ plane is larger than the cross-sectional area of the container 11b. Each of the containers 11a and 11b is a columnar (or cylindrical) body, for example, a circular cylinder or a rectangular column. FIG. 1 shows an example in which the cross-section of the container 11a along the YZ plane is circular. For example, the containers 11a and 11b are arranged so that lines passing through the center of the cross-section along the YZ plane and extending along the X direction coincide with each other. In the direction from the container 11a to 11b, the cross-sectional area along the YZ plane of the connection between the containers 11a and 11b continuously decreases. The end of container 11b in the X direction that is not connected to container 11a is open to the outside of the container and is not closed. The interior of resonator 11 is connected to the outside via container 11b. An object 14, the density of which is to be measured, is placed inside container 11a of resonator 11. Container 11a may be provided with an access port (not shown) for inserting and removing object 14. Container 11a may be provided with a stage (not shown) for placing object 14 on. Container 11a may have a shape in which the stage portion is cut out, and container 11a may be separable from the stage, and the cavity of resonator 11 may be formed by integrating container 11a and the stage.

[0016] The sound wave generating unit 12 generates sound waves within the resonator 11. The sound wave generating unit 12 is, for example, a speaker. The sound wave measuring unit 13 measures the sound waves within the resonator 11 and converts the measured sound waves into sound wave information. The sound wave measuring unit 13 is, for example, a microphone.

[0017] The sound wave generating unit 12 is disposed at one end of the container 11a in the X direction, and one end of the container 11b is connected to the other end of the container 11a. In FIG. 1, one end of the container 11a in the X direction is closed by a flat plate along the YZ plane. The flat plate may have an opening. For example, the opening is disposed so that a straight line passing through the center of the cross section of the container 11a along the YZ plane and extending along the X direction passes through the interior of the opening. The sound wave generating unit 12 is disposed, for example, outside the container 11a. The sound waves generated by the sound wave generating unit 12 are supplied into the resonator 11 from the opening of the container 11a. The sound wave measuring unit 13 is disposed at the other end of the container 11a in the X direction. For example, the sound wave measuring unit 13 is located inside a virtual columnar shape formed by extending the outer edge of the container 11b in the X direction, and is located inside the container 11b in a plan view in the X direction.

[0018] That is, the sound wave generating unit 12 is disposed at one end of the resonator 11 in the X direction, and the sound wave measuring unit 13 is disposed at the other end of the resonator 11, opposite the sound wave generating unit 12. An object 14, the object of density measurement, is placed between the sound wave generating unit 12 and the sound wave measuring unit 13 inside the resonator 11.

[0019] The configuration and arrangement of the resonator 11, sound wave generating unit 12, and sound wave measuring unit 13 in the sound wave information acquiring unit 10 are not limited to those shown in Fig. 1. Other examples will be shown in modified examples described later.

[0020] Next, the Helmholtz resonance occurring in the resonator 11 will be described with reference to Fig. 2. Fig. 2 is a conceptual diagram for explaining the Helmholtz resonance occurring in the resonator 11.

[0021] In resonator 11, in which container 11a and container 11b are connected, Helmholtz resonance occurs, which is the vibration of a spring-mass system in which the cavity of container 11a acts as a spring and the cavity of container 11b, which is the neck portion, acts as a mass, as shown in Fig. 2. A container with a structure that generates Helmholtz resonance is called a Helmholtz resonator.

[0022] In addition to the Helmholtz resonance, air column resonance also occurs inside the resonator (i.e., Helmholtz resonator) 11, in which the cavity of the container 11b, which has a smaller cross-sectional area (or volume), is virtually extended into the cavity of the other container 11a, forming a virtual resonance tube.

[0023] When an insert is installed inside the resonator 11, the frequency at which Helmholtz resonance occurs (hereinafter referred to as the Helmholtz resonance frequency) and the sound pressure of the Helmholtz resonance frequency component inside the resonator 11 change, and further the sound pressure at the frequency at which air column resonance occurs (hereinafter referred to as the air column resonance frequency) decreases.

[0024] As an example, the frequency characteristics within resonator 11 when an insert is installed within resonator 11 will be described. Figure 3 is a diagram showing the frequency characteristics when an insert is installed within resonator 11. The horizontal axis represents the frequency of the sound wave, and the vertical axis represents the sound pressure level. The inserts are two types of sponges 1 and 2 that have the same volume but different materials. The density of sponges 1 and 2 is sponge 2 > sponge 1. The frequency characteristics when no sponge is installed are shown by a solid line, the frequency characteristics when sponge 1 is installed are shown by a dashed line, and the frequency characteristics when sponge 2 is installed are shown by a dashed line.

[0025] As shown in Fig. 3, when the sponge 1 is installed in the resonator 11, the sound pressure level at the air column resonance frequency is lower than when the sponge is not installed. Furthermore, the Helmholtz resonance frequency and its sound pressure level are also lowered accordingly.

[0026] Furthermore, when sponge 2 is installed in resonator 11, the sound pressure level at the air column resonance frequency is lower than when sponge 1 is installed. Furthermore, the Helmholtz resonance frequency is also lowered accordingly.

[0027] Next, the effect of air column resonance on Helmholtz resonance will be explained using Figure 4. Figure 4(a) is a conceptual diagram showing the basic state of Helmholtz resonance. Figure 4(b) is a conceptual diagram showing the effect of air column resonance on Helmholtz resonance.

[0028] If the air column resonance does not affect the Helmholtz resonance, the frequency of the spring portion corresponding to the container 11a may fluctuate significantly, as shown in FIG. 4(a).

[0029] On the other hand, when air column resonance affects Helmholtz resonance, the frequency of the spring part corresponding to the container 11a fluctuates as shown in Figure 4(b). However, since the air column resonance acts as a restraining force on the vibration of the spring part, the frequency does not fluctuate significantly as shown in Figure 4(a).

[0030] Inside the Helmholtz resonator, the energy due to air column resonance is large. Therefore, the air column resonance acts as a force that suppresses the spring vibration in the Helmholtz resonance, causing a change in the Helmholtz resonance frequency. Therefore, if the air column resonance energy changes by installing an insert with a different density, the Helmholtz resonance frequency also shifts in conjunction with the change in air column resonance energy. In other words, the air column resonance energy and the Helmholtz resonance frequency are linked.

[0031] The linkage between air column resonance and Helmholtz resonance will be explained using Figure 5. Figure 5 is a diagram showing the relationship between changes in air column resonance and changes in Helmholtz resonance. Figure 5 shows a model of the frequency characteristics shown in Figure 3.

[0032] As shown in Figure 5, when the insert installed in the resonator 11 is changed, the air column resonance changes, and the Helmholtz resonance also changes in conjunction with the change in the air column resonance. That is, when a high-density insert is installed in the resonator 11, the air column resonance frequency decreases compared to when a low-density insert is installed, and the sound pressure level at the air column resonance frequency also decreases. The Helmholtz resonance frequency decreases in conjunction with this decrease in the air column resonance frequency and its sound pressure level.

[0033] Next, we will explain the reverberation curve measured when an insert is installed in the resonator 11 using Figures 6 and 7. Figure 6 is a diagram showing the reverberation curve when an insert is installed in the resonator 11. Figure 7 is a diagram showing the reverberation curve when no insert is installed in the resonator 11. In Figures 6 and 7, the horizontal axis represents elapsed time, and the vertical axis represents the reverberation envelope level.

[0034] The measured reverberation frequency band is a resonant frequency band that includes the Helmholtz resonance frequency (for example, a band with a center frequency of 315 Hz). The reverberation curve is a curve that shows the attenuation state of sound pressure in the resonant frequency band after sound waves are generated from the sound wave generating unit 12 and then stopped.

[0035] When no insert is installed in the resonator 11, as shown in Figure 7, the reverberation curve begins with a large attenuation as shown at D, followed by a gradual decay. On the other hand, when an insert is installed, as shown in Figure 6, the reverberation curve begins with a large first attenuation as shown at A, as in Figure 7, but midway through the first attenuation, a second attenuation occurs in which the attenuation temporarily decreases as shown at B. Furthermore, after the second attenuation, a large third attenuation occurs again as shown at C. The third attenuation is larger than the second attenuation but smaller than the first attenuation. The second attenuation is between the first and third attenuations.

[0036] In the reverberation curve shown in Figure 6, the initial large first decay indicated by A is called the initial decay, and the second decay which temporarily becomes smaller indicated by B is called the equilibrium decay. Furthermore, the slope of the reverberation curve during the period t0 when the initial decay occurs is called the initial decay slope (g0 / t0), and the slope of the reverberation curve during the period t1 when the equilibrium decay occurs is called the equilibrium decay slope (g1 / t1).

[0037] Fig. 8 shows reverberation curves measured by changing the type of insert placed in the resonator 11. Comparing the reverberation curves when the type (i.e., density) of the insert is changed, it can be seen that the slope of the initial decay and the slope of the equilibrium decay differ depending on the type of insert, as shown in Fig. 8. Therefore, the slope of the initial decay and the slope of the equilibrium decay in the reverberation curve differ depending on the type of insert, i.e., the density of the insert.

[0038] Next, the relationship between the density of the insert and the slope of the initial attenuation, and the relationship between the density of the insert and the slope of the equilibrium attenuation will be described with reference to FIGS.

[0039] 9 is a diagram showing the relationship between the density of the interpolation and the slope of the initial attenuation, where the horizontal axis represents the density and the vertical axis represents the slope of the initial attenuation.

[0040] As shown in FIG. 9, the density of the filler and the slope of the initial attenuation are inversely proportional to each other, and it can be seen that the density of the filler and the slope of the initial attenuation are relative to each other.

[0041] Therefore, by placing an object 14 in the resonator 11 and calculating the slope of the initial attenuation in the object 14, it is possible to determine the density of the object 14 from the calculated slope of the initial attenuation based on the relative relationship between the slope of the initial attenuation and the density as shown in Figure 9.

[0042] 10 is a diagram showing the relationship between the density of the insert and the slope of the equilibrium attenuation, where the horizontal axis represents density and the vertical axis represents the slope of the equilibrium attenuation.

[0043] As described above, as shown in FIG. 10, the density of the insert and the slope of the equilibrium attenuation are inversely proportional to each other, and it can be seen that the density of the insert and the slope of the equilibrium attenuation are relative to each other.

[0044] Therefore, by placing an object 14 in the resonator 11 and calculating the slope of the equilibrium damping in the object 14, it is possible to determine the density of the object 14 from the calculated slope of the equilibrium damping based on the relative relationship between the slope of the equilibrium damping and the density as shown in Figure 10.

[0045] Next, the relationship between the density of the insert and the air column resonance frequency, and the relationship between the density of the insert and the Helmholtz resonance frequency will be described with reference to FIGS. 11 and 12. FIG.

[0046] 11 is a diagram showing the relationship between the density of the insert and the air column resonance frequency, where the horizontal axis represents density and the vertical axis represents air column resonance frequency.

[0047] As shown in FIG. 11, the density of the insert and the air column resonance frequency are inversely proportional to each other, and it can be seen that the density of the insert and the air column resonance frequency have a relative relationship.

[0048] Therefore, by placing an object 14 in the resonator 11 and calculating the air column resonance frequency of the object 14, it is possible to obtain the density of the object 14 from the calculated air column resonance frequency based on the relative relationship between the air column resonance frequency and density as shown in Figure 11.

[0049] 12 is a diagram showing the relationship between the density of the insert and the Helmholtz resonance frequency, where the horizontal axis represents density and the vertical axis represents Helmholtz resonance frequency.

[0050] As described above, as shown in FIG. 12, the density of the insert and the Helmholtz resonance frequency are inversely proportional to each other, and it can be seen that the density of the insert and the Helmholtz resonance frequency have a relative relationship.

[0051] Therefore, by placing an object 14 in the resonator 11 and calculating the Helmholtz resonance frequency of the object 14, it is possible to obtain the density of the object 14 from the calculated Helmholtz resonance frequency based on the relative relationship between the Helmholtz resonance frequency and density as shown in Figure 12.

[0052] 2. Operation of the embodiment Next, an operation of the density determining device 1 according to the embodiment for determining the density of the object 14 will be described. Fig. 13 is a flow chart showing an outline of the flow of the density determining process in the density determining device 1 according to the embodiment.

[0053] First, an object 14 is placed in the resonator 11, and sound waves are generated in the resonator 11 from the sound wave generating unit 12. The sound wave information acquiring unit 10 measures the sound waves in the resonator 11 and acquires sound wave information A1 and A2 (S11).

[0054] The acoustic wave information A1 acquired by the acoustic wave information acquisition unit 10 is input to the resonance frequency calculation unit 20. The resonance frequency calculation unit 20 calculates resonance frequencies (for example, air column resonance frequencies and Helmholtz resonance frequencies) using the acoustic wave information A1 (S12a).

[0055] Furthermore, the sound wave information A2 measured by the sound wave information acquisition unit 10 is input to the reverberation characteristics calculation unit 30. The reverberation characteristics calculation unit 30 calculates reverberation parameters (for example, the slope of the initial decay and the slope of the equilibrium decay) using the sound wave information A2 (S12b).

[0056] The resonance frequencies and reverberation parameters calculated by the resonance frequency calculation unit 20 and the reverberation characteristics calculation unit 30 are input to the density determination unit 40. The density determination unit 40 determines (or estimates) the density of the object 14 from the calculated resonance frequencies and reverberation parameters using prediction formula 1, which is set based on the correlation between the resonance frequencies and densities calculated in advance for a plurality of interpolations (or objects), and prediction formula 2, which is set based on the correlation between the reverberation parameters and densities calculated in advance for a plurality of interpolations (or objects) (S13).

[0057] 13 shows an example in which step S12a and step S12b are executed in parallel, but step S12a and step S12b do not have to be executed in parallel. Step S12a may be executed first, and then step S12b, or conversely, step S12b may be executed first, and then step S12a.

[0058] The operation of determining the density of the objects 14 in the density determining device 1 will be described in detail below with reference to Fig. 14. Fig. 14 is a flow chart showing a detailed flow of the density determining process in the density determining device 1 according to the embodiment.

[0059] First, the density determination process using the resonance frequency will be described.

[0060] An object 14 is placed within the resonator 11. The sound wave generating unit 12 generates sound waves within the resonator 11. The sound wave measuring unit 13 measures the sound waves within the resonator 11 and outputs sound wave information A1 as the measurement result. Here, for example, the sound wave generating unit 12 continues to generate a predetermined sound wave, and the sound wave measuring unit 13 measures the sound waves within the resonator 11 while the sound waves are being generated from the sound wave generating unit 12. As a result, the sound wave measuring unit 13 acquires the sound wave information A1 and outputs the sound wave information A1 to the resonance frequency calculating unit 20.

[0061] Next, the resonant frequency calculation unit 20 measures the frequency characteristics of the sound waves in the resonator 11 from the sound wave information A1 (S21).

[0062] Furthermore, the resonant frequency calculation section 20 generates a frequency spectrum from the measured frequency characteristics (S22).

[0063] Next, the resonance frequency calculation unit 20 calculates the resonance frequencies occurring in the resonator 11, i.e., the air column resonance frequency and the Helmholtz resonance frequency, from the generated frequency spectrum. Then, the resonance frequency calculation unit 20 outputs the air column resonance frequency and the Helmholtz resonance frequency to the density determination unit 40 (S23). The air column resonance frequency is a frequency having a peak sound pressure in the frequency band of the air column resonance. The Helmholtz resonance frequency is a frequency having a peak sound pressure in the frequency band of the Helmholtz resonance.

[0064] Next, the density determination unit 40 determines the density of the object 14 from the received air column resonance frequency and / or Helmholtz resonance frequency, i.e., from at least one of them, using prediction formula 1 (S24). Prediction formula 1 is a formula determined in advance based on the correlation between multiple air column resonance frequencies and the densities of multiple inserts (or objects) when multiple inserts are installed in the resonator 11, and / or a formula determined in advance based on the correlation between multiple Helmholtz resonance frequencies and the densities of multiple inserts when multiple inserts are installed in the resonator 11. Any method can be used to fit prediction formula 1. Variables in prediction formula 1 include one or both of the air column resonance frequency and the Helmholtz resonance frequency.

[0065] Next, the density determination process using the reverberation parameters will be described.

[0066] An object 14 is placed within the resonator 11. The sound wave generating unit 12 generates sound waves within the resonator 11, for example, for an extremely short, predetermined time, and then stops generating the sound waves. The sound wave measuring unit 13 then measures the attenuation of the sound waves within the resonator 11 and outputs sound wave information A2 as the measurement result. As a result, the sound wave measuring unit 13 acquires the sound wave information A2 and outputs the sound wave information A2 to the reverberation characteristic calculating unit 30.

[0067] Next, the reverberation characteristics calculation unit 30 measures the impulse response in the resonator 11 from the sound wave information A2 (S31). That is, the reverberation characteristics calculation unit 30 measures the sound pressure level in the resonator 11, which attenuates over time, immediately after a sound wave is generated from the sound wave generation unit 12. The frequency band of the measured sound pressure level is, for example, a resonance frequency band including Helmholtz resonance (for example, a band with a center frequency of 315 Hz).

[0068] Furthermore, the reverberation characteristics calculation unit 30 generates a reverberation curve, with the horizontal axis representing time and the vertical axis representing sound pressure level, from the measured impulse response (S32).

[0069] Next, the reverberation characteristics calculation unit 30 calculates the initial decay slope and the balanced decay slope as reverberation parameters from the generated reverberation curve (S33).The reverberation characteristics calculation unit 30 then outputs the calculated initial decay slope and balanced decay slope to the density determination unit 40.

[0070] Next, the density determination unit 40 determines the density of the object 14 from the received slope of the initial attenuation and / or the slope of the equilibrium attenuation, i.e., from at least one of them, using prediction formula 2 (S34). Prediction formula 2 is a formula set in advance based on the correlation between the slopes of multiple initial attenuations and the densities of multiple inserts when multiple inserts are installed in the resonator 11, and / or a formula set in advance based on the correlation between the slopes of multiple equilibrium attenuations and the densities of multiple inserts when multiple inserts are installed in the resonator 11. Any method can be used to fit prediction formula 2. The variables of prediction formula 2 include one or both of the slope of the initial attenuation and the slope of the equilibrium attenuation.

[0071] Then, the density determining unit 40 determines the density of the object 14 based on the density determined by the prediction formula 1 and the density determined by the prediction formula 2.

[0072] The density determination unit 40 determines the density of the object 14 using the above-mentioned prediction formulas 1 and 2, and for example, this determination is performed by the following method.

[0073] The frequency characteristics of multiple interpolated objects with different densities are measured in advance. The density determination unit 40 stores data on the density and frequency characteristics of the interpolated objects or a prediction formula 1 created based on the data. As shown by 2 in Figure 14, the Helmholtz resonance frequencies of the interpolated objects from highest density to lowest density can be arranged in the order C, D, A, E, and B. The Helmholtz resonance frequency of the target object 14 is also designated as X.

[0074] Here, when the Helmholtz resonance frequency X of the object 14 is calculated by the resonance frequency calculation unit 20, it is found that the Helmholtz resonance frequency X is between D and A. In such a case, it is determined that the density of the object 14 is between the density of the insert whose Helmholtz resonance frequency is D and the density of the insert whose Helmholtz resonance frequency is A.

[0075] The reverberation parameters of multiple interpolations with different densities are measured in advance. The density determination unit 40 stores data on the densities and reverberation parameters of the interpolations, or a prediction formula 2 created based on the data. As shown by 2 in Figure 14, the initial attenuation slopes of the interpolations from highest density to lowest density can be arranged in the order C, D, A, E, and B. The initial attenuation slope of the target object 14 is also designated as X.

[0076] Here, when the resonant frequency calculation unit 20 calculates the slope X of the initial attenuation of the object 14, it is found that the slope X of the initial attenuation is between D and A. In such a case, it is determined that the density of the object 14 is between the density of the interpolated object whose slope of the initial attenuation is D and the density of the interpolated object whose slope of the initial attenuation is A.

[0077] If the density value based on the resonance frequency matches the density value based on the reverberation parameters, the value is determined to be the density of the object 14 .

[0078] With the above, the density determination process in the density determining device 1 is completed.

[0079] 3. Variations Next, a modified example of the acoustic wave information acquisition unit 10 in the embodiment will be described.

[0080] As described above, the sound wave information acquisition unit 10 includes the resonator 11 in which the container 11a and the container 11b are connected, the sound wave generation unit 12, and the sound wave measurement unit 13. However, the arrangement of the resonator 11, the sound wave generation unit 12, and the sound wave measurement unit 13 is not limited to the arrangement shown in FIG.

[0081] 15 to 19 are diagrams showing other examples of the arrangement of the resonator 11, the sound wave generating unit 12, and the sound wave measuring unit 13. FIG.

[0082] FIG. 15 is a diagram showing the arrangement of the acoustic wave information acquisition section 10 according to the first modification.

[0083] In Modification 1, sound wave generating unit 12 is disposed at one end of container 11a in the X direction, and one end of container 11b is connected to the other end of container 11a. Waveguide 15 is disposed at the other end of container 11b. The main body of sound wave generating unit 12 is provided outside container 11a (or resonator 11). Sound waves generated from sound wave generating unit 12 are supplied into resonator 11 from an opening provided at one end of container 11a. Furthermore, sound wave measuring unit 13 is disposed within waveguide 15. Note that sound wave measuring unit 13 may also be disposed within container 11b. Even in Modification 1 with such an arrangement, it is possible to obtain information similar to sound wave information A1 and A2 obtained in the configuration shown in FIG. 1.

[0084] FIG. 16 is a diagram showing the arrangement of the acoustic wave information acquisition section 10 according to the second modification.

[0085] In Modification 2, sound wave generator 12 is disposed at one end of container 11a in the X direction, and one end of container 11b is connected to the other end of container 11a. The main body of sound wave generator 12 is provided inside container 11a. Furthermore, sound wave measurement unit 13 is disposed at the other end of container 11a in the X direction. Note that sound wave measurement unit 13 may also be disposed inside container 11b. In the X direction, object 14 or a stage (not shown) is located between sound wave generator 12 and sound wave measurement unit 13. Even in Modification 2 with such an arrangement, it is possible to obtain information similar to sound wave information A1 and A2 obtained in the configuration shown in FIG. 1.

[0086] FIG. 17 is a diagram showing the arrangement of the acoustic wave information acquisition section 10 according to the third modification.

[0087] In Modification 3, sound wave generating unit 12 is disposed at one end of container 11a in the X direction, and one end of container 11b is connected to the other end of container 11a. Waveguide 15 is disposed at the other end of container 11b. The main body of sound wave generating unit 12 is provided inside container 11a. Furthermore, sound wave measuring unit 13 is disposed within waveguide 15. Note that sound wave measuring unit 13 may also be disposed within container 11b. Even in Modification 3 with such an arrangement, it is possible to obtain information similar to sound wave information A1 and A2 obtained in the configuration shown in FIG.

[0088] FIG. 18 is a diagram showing the arrangement of the acoustic wave information acquisition section 10 according to the fourth modification.

[0089] In Modification 4, sound wave generating unit 12 is disposed at one end of container 11a in the X direction, and one end of container 11b is connected to the other end of container 11a. The main body of sound wave generating unit 12 is provided outside container 11a. One end of container 11a has no wall material, and is open. Sound waves generated from sound wave generating unit 12 are supplied into resonator 11 from the open end of container 11a. Furthermore, sound wave measuring unit 13 is disposed on the other end side of container 11a in the X direction. Note that sound wave measuring unit 13 may also be disposed inside container 11b. Even in Modification 4 with such an arrangement, it is possible to obtain information similar to sound wave information A1 and A2 obtained in the configuration shown in FIG. 1.

[0090] FIG. 19 is a diagram showing the arrangement of the acoustic wave information acquisition section 10 according to the fifth modification.

[0091] In Modification 5, sound wave generating unit 12 is disposed at one end of container 11a in the X direction, and one end of container 11b is connected to the other end of container 11a. Waveguide 15 is disposed at the other end of container 11b. The main body of sound wave generating unit 12 is provided outside container 11a. One end of container 11a has no wall material, and is open. Sound waves generated from sound wave generating unit 12 are supplied into resonator 11 from the open end of container 11a. Furthermore, sound wave measuring unit 13 is disposed in waveguide 15. Note that sound wave measuring unit 13 may also be disposed in container 11b. Even in Modification 5 with such an arrangement, it is possible to obtain information similar to sound wave information A1 and A2 obtained in the configuration shown in FIG. 1.

[0092] 4. Hardware Configuration of the Embodiment Next, an example of the hardware configuration of the density determination device 1 (excluding the sound wave information acquisition unit 10) will be described. That is, here, an example will be described in which the resonance frequency calculation unit 20, the reverberation characteristics calculation unit 30, and the density determination unit 40 are configured by a computer 60.

[0093] 20 is a diagram showing an example of the hardware configuration of the resonance frequency calculation unit 20, the reverberation characteristics calculation unit 30, and the density determination unit 40 in the density determination device 1 according to the embodiment. The density determination device 1 (i.e., the computer 60) excluding the sound wave information acquisition unit 10 has a processor 61, a ROM (Read Only Memory) 62, a RAM (Random Access Memory) 63, an auxiliary storage device 64, and an input / output interface 65.

[0094] The processor 61, ROM 62, RAM 63, auxiliary storage device 64, and input / output interface 65 are electrically connected to one another via a bus 66, and are capable of exchanging data and signals with one another via the bus 66.

[0095] The processor 61 is configured by, for example, a general-purpose hardware processor including a CPU (Central Processing Unit), etc. The processor 61 controls the ROM 62, the RAM 63, the auxiliary storage device 64, and the input / output interface 65 as a whole.

[0096] The ROM 62 is a non-volatile memory that constitutes part of the main storage device. The ROM 62 non-temporarily stores a startup program required when starting up the density determination device 1. The density determination device 1 starts up when the processor 61 executes the program in the ROM 62. The ROM 62 is configured, for example, with an EPROM (Erasable Programmable Read Only Memory), and stores various settings at startup in addition to the startup program.

[0097] The RAM 63 is a volatile memory that constitutes part of the main storage device. The RAM 63 temporarily stores programs required for processing by the processor 61 and data required for executing the programs. The processor 61 executes the programs in the RAM 63 to perform operations on the data in the RAM 63 and store the results of the operations in the RAM 63.

[0098] The auxiliary storage device 64 is configured by a non-volatile memory such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive). The auxiliary storage device 64 non-temporarily stores programs to be executed by the processor 61 and data required for executing the programs. The processor 61 loads the programs and data in the auxiliary storage device 64 into the RAM 63 and executes the programs to perform various functions.

[0099] The input / output interface 65 is connected to an external input device 71, an output device 72, etc., and enables input of information from the input device 71 and output of information to the output device 72. For example, the input / output interface 65 may be a wired interface or a wireless interface. The wired interface includes a port to which a device is connected, etc. The wireless interface includes Bluetooth (registered trademark), Wi-Fi (registered trademark), etc. The input device 71 may include a keyboard, a mouse, a touch panel, a receiving device, a disk drive, etc. The input device 71 is not limited to these and may include any other input device. The output device 72 may include a display, a transmitting device, a disk drive, etc. The output device 72 is not limited to these and may include any other output device. The input device 71 and the output device 72 may be configured as an input / output device 73 that has the functions of both the input device 71 and the output device 72.

[0100] Input data, for example, sound wave information A1 and A2 output from the sound wave information acquisition unit 10, is input to a computer 60 including an input / output interface 65 via an input device 71. That is, the sound wave information A1 and A2 is input via the input device 71 to the computer 60 functioning as a resonance frequency calculation unit 20, a reverberation characteristics calculation unit 30, and a density determination unit 40.

[0101] When the computer 60 starts up, the processor 61 executes a program in the ROM 62 and loads and starts an operating system (OS) into the RAM 63. Under the control of the OS, the processor 61 monitors input instructions, connections to external devices, etc. Also, under the control of the OS, the processor 61 sets up a program area and a data area in the RAM 63.

[0102] In response to an instruction to start the density determination apparatus 1, the processor 61 loads a program related to the density determination process to be executed by the density determination apparatus 1 from the auxiliary storage device 64 into the program area of the RAM 63. Furthermore, the processor 61 loads data required for executing the program related to the density determination process from the auxiliary storage device 64 into the data area of the RAM 63. The processor 61 calculates the data in the data area in accordance with the program related to the density determination process and writes the calculation results to the data area. Through these operations, the processor 61, RAM 63, auxiliary storage device 64, input / output interface 65, and bus 66 work together to execute at least some of the functions of the components of the density determination apparatus 1, namely, the resonance frequency calculation unit 20, the reverberation characteristics calculation unit 30, and the density determination unit 40.

[0103] 5. Effects of the embodiment According to this embodiment, it is possible to provide a density determination device and method capable of improving density measurement performance.

[0104] In this embodiment, the resonance frequency when an object 14 is placed inside the resonator 11 is calculated, and the density of the object 14 is calculated from the calculated resonance frequency based on Prediction Formula 1. The resonance frequency includes an air column resonance frequency and / or a Helmholtz resonance frequency. Prediction Formula 1 is an equation set from the correlation between the air column resonance frequency and the density for multiple objects, and / or an equation set from the correlation between the Helmholtz resonance frequency and the density.

[0105] Furthermore, reverberation parameters when an object 14 is placed in the resonator 11 are calculated, and the density of the object 14 is calculated from the calculated reverberation parameters based on Prediction Formula 2. The reverberation parameters include the slope of initial decay (e.g., g0 / t0 in FIG. 6) and / or the slope of equilibrium decay (e.g., g1 / t1 in FIG. 6) obtained from the reverberation curve (or reverberation characteristics) when the object 14 is placed in the resonator 11. Prediction Formula 2 is an equation set based on the correlation between the slope of initial decay and the density for multiple interpolated objects, and / or an equation set based on the correlation between the slope of equilibrium decay and the density. The density calculated by Prediction Formulas 1 and 2 is then used to determine the density of the object 14. The method for determining the density of the object 14 is not particularly limited. The density calculated by Prediction Formulas 1 and 2 may be averaged to determine the density of the object 14. The value calculated by weighting the values calculated by prediction formulas 1 and 2 according to the material properties of the object 14 may be determined as the density of the object 14. For example, the sum of the value calculated by prediction formula 1 multiplied by a constant k between 0 and 1 and the value calculated by prediction formula 2 multiplied by (1-k) may be determined as the density of the object 14. When either the resonance frequency or the reverberation characteristics falls within a predetermined range where the fitting accuracy of the prediction formula is poor, the value obtained by a prediction formula using the other may be determined as the density of the object 14. The numerical range between the density value based on the resonance frequency and the density value based on the reverberation parameters may be determined as the density of the object 14.

[0106] As described above, in this embodiment, the density of the object 14 is determined from the calculated resonance frequencies and reverberation parameters using at least one prediction formula set from the correlation between the density and the resonance frequencies or reverberation parameters for a plurality of interpolated objects. This improves the density measurement performance of the density determination device 1. Since a common configuration is used for the two types of density measurement, the density determination device 1 can be easily realized in a small size.

[0107] Furthermore, in this embodiment, the object 14 is placed inside the resonator 11, and the density of the object 14 is determined using sound wave information obtained by measuring sound waves inside the resonator 11. Therefore, when measuring the density of the object 14, the method is non-contact and non-destructive to the object 14, and no pressure is applied to the object 14. Therefore, the density of the object 14 can be measured without causing any change in shape or deterioration in quality of the object 14.

[0108] In the above-described embodiments, the functional blocks can be realized as either hardware or computer software, or a combination of both. It is not necessary for the functional blocks to be distinguished as in the above-described examples. For example, some functions may be performed by functional blocks other than the illustrated functional blocks. Furthermore, the illustrated functional blocks may be further divided into smaller functional sub-blocks. Furthermore, the order of the processes in the flowcharts described in the embodiments can be changed as much as possible.

[0109] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are intended to be included within the scope and spirit of the invention, as well as within the scope of the inventions and their equivalents as set forth in the claims. [Explanation of symbols]

[0110] 1...density determination device, 10...sound wave information acquisition unit, 11...resonator, 11a...container, 11b...container, 12...sound wave generation unit, 13...sound wave measurement unit, 14...target object, 15...waveguide, 20...resonance frequency calculation unit, 30...reverberation characteristic calculation unit, 40...density determination unit, 60...computer, 61...processor, 62...ROM, 63...RAM, 64...auxiliary storage device, 65...input / output interface, 66...bus, 71...input device, 72...output device, 73...input / output device, A1...sound wave information, A2...sound wave information.

Claims

1. a container in which the object can be placed; a sound wave generating unit that generates sound waves within the container; a sound wave measuring unit that measures sound waves in the container and outputs first sound wave information, and that measures reverberation in the container and outputs second sound wave information; a resonance frequency calculation unit that calculates a resonance frequency of resonance occurring in the container using the first sound wave information; a reverberation characteristics calculation unit that calculates a reverberation parameter related to the reverberation using the second sound wave information; a density determination unit that determines the density of the object based on the resonance frequency and the reverberation parameters; A density determination device comprising:

2. The resonant frequency includes at least one of a frequency of an air column resonance occurring in the container or a frequency of a Helmholtz resonance occurring in the container. The density determination device according to claim 1 .

3. the reverberation in the container has, in a reverberation curve indicating a sound pressure level that changes over time, a first attenuation that occurs early and has a large attenuation, and a second attenuation that occurs after the first attenuation and has a smaller attenuation than the first attenuation, the reverberation parameters include at least one of a slope of the first decay or a slope of the second decay; The density determination device according to claim 2 .

4. the reverberation has a third decay that occurs after the second decay and has a greater decay than the second decay; the second attenuation is between the first attenuation and the third attenuation; The density determination device according to claim 3 .

5. the frequency band of the reverberation measured by the sound wave measuring unit includes a band including a frequency of Helmholtz resonance occurring in the container, The density determination device according to claim 1 .

6. The density determination unit performing a first determination of the density of the object from the resonant frequency calculated by the resonant frequency calculation unit using a first equation set based on a correlation between a plurality of resonant frequencies when a plurality of objects are placed in the container and the densities of the plurality of objects; performing a second determination of the density of the object from the reverberation parameters calculated by the reverberation characteristics calculation unit using a second equation set based on a correlation between a plurality of reverberation parameters and a density of the plurality of objects when the plurality of objects are placed in the container; determining a density of the object based on the first determination and the second determination; The density determination device according to claim 1 .

7. the plurality of resonance frequencies and the resonance frequency calculated by the resonance frequency calculation unit include at least one of a frequency of air column resonance occurring in the container or a frequency of Helmholtz resonance occurring in the container; The density determination device according to claim 6.

8. the reverberation in the container has, in a reverberation curve indicating a sound pressure level that changes over time, a first attenuation that occurs early and has a large attenuation, and a second attenuation that occurs after the first attenuation and has a smaller attenuation than the first attenuation, the plurality of reverberation parameters and the reverberation parameter calculated by the reverberation characteristics calculation unit include at least one of the first attenuation slope and the second attenuation slope; The density determination device according to claim 7.

9. The container includes a first container in which the object is placed and a second container having a smaller volume than the first container, The first container and the second container are connected to each other. The density determination device according to claim 1 .

10. The density determining device according to claim 9 , wherein the sound wave generating unit is disposed at one end of the first container, and the sound wave measuring unit is disposed at the other end of the first container.

11. the sound wave generating unit is disposed outside the first container at one end of the first container, and the sound wave measuring unit is disposed at the other end of the first container; The density determining device according to claim 9 , wherein the sound wave generating unit generates sound waves into the first container from an opening provided at one end of the first container.

12. the vessel further comprises a waveguide; the sound wave generating unit is disposed at one end of the first container, the second container is connected to the other end of the first container, the waveguide is connected to the other end of the second container, and the sound wave measuring unit is disposed in the waveguide; The density determining device according to claim 9.

13. The density determining device according to claim 9 , wherein each of the first container and the second container includes a columnar body or a cylindrical body.

14. The density determining device of claim 9 , wherein each of the first container and the second container comprises either a cylinder or a prism.

15. A density determination method for determining the density of an object in a container in which the object can be placed, comprising: generating acoustic waves within the vessel; measuring sound waves within the container and outputting first sound wave information, and measuring reverberation within the container and outputting second sound wave information; Calculating a resonant frequency of resonance occurring in the container using the first sound wave information; calculating a reverberation parameter related to the reverberation using the second sound wave information; determining a density of the object based on the resonant frequency and the reverberation parameters; A density determination method comprising:

16. The determination of the density of the object comprises: a first determination of determining the density of the object from the resonant frequency calculated from the first sound wave information using a first equation set based on a correlation between a plurality of resonant frequencies when a plurality of objects are placed in the container and the densities of the plurality of objects; a second determination of the density of the object from the reverberation parameters calculated from the second sound wave information using a second equation set based on a correlation between a plurality of reverberation parameters and a density of the plurality of objects when the plurality of objects are placed in the container; determining a density of the object based on the first determination and the second determination; The method of claim 15, comprising:

17. The resonant frequency includes at least one of a frequency of an air column resonance occurring in the container or a frequency of a Helmholtz resonance occurring in the container. The density determination method of claim 15.

18. the reverberation in the container has, in a reverberation curve indicating a sound pressure level that changes over time, a first attenuation that occurs early and has a large attenuation, and a second attenuation that occurs after the first attenuation and has a smaller attenuation than the first attenuation, the reverberation parameters include at least one of a slope of the first decay or a slope of the second decay; The density determination method of claim 15.

19. The reverberation frequency band includes a band including a frequency of Helmholtz resonance occurring in the container. The density determination method of claim 15.

20. The container includes a first container in which the object is placed and a second container having a smaller volume than the first container, The first container and the second container are connected to each other. The density determination method of claim 15.

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