JP2007192801A - Measuring method of elasticity using sound wave - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide measuring method of elasticity which can visually clarify any external environmental condition subtly affecting nonlinear elasticity of an elastomer, such as humidity, temperature or sunshine impact to building materials or vegetables, effects of fatigue, stress or food subtly changing elasticity of human skin, etc., and also can derive a noncontact measurement of these external environmental conditions from measurement of reflected sound to easily be quantifiable. <P>SOLUTION: The system used for this measuring method is designed so that sound wave is emitted towards a measurement object 1 from a speaker 2 in location separated from the measurement object 1, reflected sound from it is received and analyzed in microphone 3 positioned away from the measurement object 1, to quantify any effect of external factors such as temperature, humidity, etc. on elasticity of the measurement object 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention has a wide range of elasticity, such as freshness measurement according to storage conditions such as humidity and temperature of vegetables, measurement of characteristic changes to environmental conditions such as humidity, temperature and solar radiation of sound insulation building materials, measurement of thermal characteristics of plastic materials, aging diagnosis of human skin, etc. The present invention relates to a method for measuring a change in characteristics of a material having characteristics and a method for measuring an elastic characteristic using sound waves applied to diagnosis.

Traditionally, vegetable freshness diagnostics, human skin aging diagnostics, thermal properties of plastic materials and changes in environmental properties such as humidity, temperature, and solar radiation of sound insulation building materials have been qualitatively evaluated by visual and stress measurements, and without contact Detailed measurement methods that clarify the cause and effect of various factors of change have not fully met social needs. Among them, an oscillator that generates vibrations near 200 Hz is brought into contact with vegetables, and attempts are made to evaluate the freshness of vegetables from changes in the waveform of vibrations that have passed through them. There is evidence of a new diagnostic method, such as diagnosing aging of human skin, from the change in the reflected light intensity of the laser light in the hollow, which is signaled as a chaotic response based on the nonlinear elastic properties of the elastic body. No qualitative or quantitative evaluation has been achieved, and it has not been established as a simple non-contact measurement method.
JP 2004-188213 A JP 2001-137240 A

  For example, in an attempt to evaluate the freshness of a vegetable from the change in the waveform of vibration that has passed through the vegetable based on the nonlinear characteristics of elasticity, even if the change over time of the vegetable can be measured by visual and stress changes alone, Evaluation of the relationship between various factors of storage conditions such as temperature, humidity, and solar radiation has not been achieved, and for skin aging evaluation, the return change of the depression formed by the shock wave of air can be measured by reflection measurement of laser light. However, there is a problem that it is only presenting changes over time and rate of change.

  As a method of solving the above problem, in the present invention, when an elastic body having nonlinear characteristics is subjected to vibration from the outside, the response from the elastic body becomes chaotic, which is a minute change in the nonlinearity of the elastic body, and the response signal waveform. When this signal is changed on the X-axis and the signal to which the phase lag is given is changed on the Y-axis and superimposed on the XY rectangular coordinate display device, the loop shape does not pass through the same trajectory. A non-recursive orbit figure centered on a certain coordinate called a so-called attractor changes greatly, so external environment conditions that give minute changes to the nonlinear elastic properties of elastic bodies, such as humidity and temperature for building materials and vegetables The effect of sunlight, fatigue that gives minute changes to human skin elasticity, stress, food, and other effects can be clearly determined visually. It is intended to.

  The present invention includes a measurement object whose elasticity characteristics are measured, a speaker that is disposed apart from the measurement object and outputs sound waves having an audible frequency, and a microphone that collects reflected sound from the measurement object. The reflected sound from the microphone is AD-converted, a chaotic non-periodic change figure is displayed on a display device, and the elastic characteristic of the measurement object is measured by non-contact measurement.

  Further, in the present invention, the sound wave of the audible frequency is alternately output in a pulse shape and added to the measurement object, and the reflected sound is cut out and coupled to the display device using a chaotic aperiodic change. The figure is displayed.

  Furthermore, the present invention is characterized in that the microphone is coaxially arranged on the front surface of the speaker, and the reflected sound from the measurement object is cut out and collected.

  Further, in the present invention, an XY orthogonal coordinate display device is used as the display device, and the elastic characteristics of the measurement object are determined by a change in the attractor drawn by adding the received wave shape and the signal after the phase delay processing to the respective coordinates. Is measured.

  Furthermore, the present invention is characterized in that the phase delay processing is performed for three sample periods.

  According to the present invention, qualitative and can only be displayed over time, for example, freshness measurement under storage conditions such as humidity and temperature of vegetables, measurement of characteristic changes with respect to environmental conditions such as humidity, temperature and solar radiation of sound insulation materials, plasticity Non-contact measurement and evaluation of thermal characteristics of materials and aging diagnosis of human skin can be performed more precisely than ever.

  In the present invention, sound waves are used for non-contact, harmless to food and living bodies, and in addition to a speaker and a microphone, the device is an analog-digital converter and a personal computer. In recent years, an analog-digital converter is built into a personal computer and is compact. Therefore, since the apparatus is simple and easy to carry, there is a high applicability that it can be transported to the site where the harvest of vegetables is evaluated and the construction site.

  Furthermore, in the present invention, an attractor using a reflected wave period extraction combined waveform made from an output waveform from a microphone and using an embedded dimension of 2 and a delay time τ = 3 samples can be displayed. The attractor figure can be displayed in an easy-to-understand manner on the Y rectangular coordinate display device.

  Furthermore, in the present invention, by drawing the attractor to the delay time τ = 3 sample periods, it is possible to display the attractor with the most change.

  Hereinafter, a method for measuring characteristics of an elastic body based on a nonlinear response of sound waves and a simple measuring apparatus embodying the same will be described with reference to the drawings.

  In this embodiment, the measurement object 1 such as a plaster board or plywood shown in FIG. 1 is targeted, and a 2 ms square wave signal optimized from the transmission and reception of sound waves is generated by the oscillator 6 every 20 ms, and the sound insulation is performed. A sound wave is projected from the speaker 2 in the box 4 to the measurement object 1 and is caused to vibrate on the surface of the measurement object 1 which is an elastic body, and the reflected sound from the surface of the measurement object 1 at that time is sound-insulated. The sound is received by the microphone 3 arranged so as to block the sound generated from the speaker 2 by the partition wall 5, the signal is digitally converted by the analog-to-digital converter 9, the attractor is drawn by the personal computer 10, and the measurement object 1 It is configured to evaluate changes due to various factors from figures.

  The attractor according to the present invention displays the reflected sound 8 shown in FIG. 2 from the object to be measured by the microphone 3, converts the signal to the digital signal 12 by the analog-digital converter 9, and outputs the signal as it is. 2 is added to the horizontal axis 14 of the display orthogonal coordinate screen, that is, the X-axis, and the received sound signal is sent from the received signal by τ seconds by the phase delay unit 11 of FIG. In addition to the vertical axis 15 of the coordinate screen, that is, the Y axis, a signal trajectory figure is drawn as the attractor 16 in FIG. 2, and the influence of various factors that affect the elastic characteristics of the measurement target is displayed. It is configured so that it can be evaluated as an orbital figure.

  Next, specific experimental methods and conditions will be described with reference to FIG. The experiment was conducted in a general classroom, not in an anechoic room. Using a classroom with a height of 600 cm, a width of 700 cm, and a height of 280 cm, the speaker 3, the microphone 2 and the measurement object 1 are arranged at a height of 104 cm from the floor, and the microphone 2 is arranged coaxially on the front surface of the speaker 3. Then, the tip portions of both are separated by 44 cm, and the tip portion of the microphone 2 and the measurement object 1 are arranged by 60 cm apart. The classroom wall and the speaker 3, the microphone 2 and the measurement object 1 are sufficiently separated from each other, and the sound wave from the speaker 3 is reflected from the classroom wall until the reflected sound from the measurement object 1 reaches the microphone 2. Consideration is given so that it is not collected by the microphone 2. FIG. 3 is a top view of the classroom as viewed from the ceiling. 3 is different from the arrangement shown in FIG. 1, various arrangements are possible.

  As the measurement object 1, board paper, wood, polystyrene foam, aluminum sheet, and vegetables (cabbage, radish) were used.

  A commercially available notebook personal computer was used as the XY rectangular coordinate display device, an audio capture was used as the oscillator 6, a sharp directivity condenser microphone was used as the microphone 2, and a woofer was used as the speaker 3. The analog-digital converter 9 has a sampling frequency of 44.1 kHz and a quantization bit number of 16 bits.

  Next, an output sound wave (probe wave) from the speaker will be described with reference to FIG. As shown in FIG. 4, the output sound wave uses a repeated pulse waveform having a pulse width of 2 msec every 20 msec. That is, the sound wave output period 2 msec and the silence period 18 msec are alternately output in a pulse state. A sound wave having an audible frequency that is a natural vibration region of the measurement object is selected, and a 2 ms square wave pulse is generated every 20 ms. Since the sound wave is in the natural vibration region of the measurement object, the nonlinear elastic characteristic of the measurement object of the measurement object is induced by the sudden change of the generated square wave pulse, and the minute change in elasticity can be evaluated, making it easy to understand This is because an attractor is obtained.

  Further, the reflected wave period extraction combined waveform used for displaying the attractor will be described with reference to FIGS. 5 and 6. FIG.

  The reflected wave arrives at the microphone after τ seconds.

τ = distance 60 cm × 2 / sound speed 340000 cm · sec ⁻¹ = 3.5 msec
From this calculation formula, the reflected wave is collected in the microphone in 3.5 msec.

  FIG. 5 shows an actual output waveform from the microphone. A portion indicated by a is a sound wave output period, and a time period of 2 msec after 3.5 msec, which is a time when a reflected wave arrives, that is, an output waveform of a portion indicated by b is taken out and sequentially combined. The reflected wave period extraction combined waveform shown in FIG.

  Fig. 6 (a) shows a case where no measurement object is placed, and no reflected wave is included. When this waveform is compared with other waveforms, it can be seen that the waveform changes in a complicated manner due to reflection from the measurement object. It can also be seen that the continuous waveform changes slightly even for the same object to be measured, and is not a repetition of the same waveform.

  6 (b) is a dry board, FIG. 6 (c) is a wet board, FIG. 6 (d) is an aluminum sheet, FIG. 6 (e) is a wooden board, FIG. 6 (f) is a polystyrene foam, FIG. 6G shows a leaf cabbage, and FIG. 6H shows a combined waveform extracted from the reflected wave period of the radish.

  Drawing of the attractor will be described based on the reflected wave period extraction combined waveform shown in FIG.

From the time series data x (t) of the reflected sound waveform, the horizontal axis is x (t), the vertical axis is x (t + τ),
v (t) = (x (t), x (t + τ))
The attractor v (t) due to the time delay shown in FIG. t indicates the number of samples, and τ indicates the delay time. Discontinuous points that occur when combining waveforms are processed so as not to affect the attractor.

  FIG. 7 shows an attractor employing the reflected wave period extraction combined waveform shown in FIG. 6 and employing an embedding dimension of 2 and a delay time τ = 3 samples. The delay time τ = 3 samples means that the numerical value at the time of sampling of the third p pulse is used, and the change appears most in the attractor during the delay time τ = 3 sample periods.

  FIG. 7A shows a case where no measurement object is placed, FIG. 7B shows a dry board, FIG. 7C shows a wet board, and FIG. 7D shows aluminum. 7 (e) shows a wooden board, FIG. 7 (f) shows a polystyrene foam, FIG. 7 (g) a leaf cabbage, and FIG. 7 (h) shows a radish attractor. In this attractor, changes in elastic properties due to the material remarkably appear in the lower left part and the upper right part. In order to quantify the change of the attractor, the number of holes of the attractor, the number of windings, and the volume of the figure when three-dimensionally displayed can be considered.

Considering the softness of the material as a standard, the board is in the order of wet board paper, cabbage, aluminum sheet, polystyrene foam, radish, dry board paper, and wood board. You can see that it increases. In addition, the winding size of the lower left part also changes depending on the softness of the material.

  The present invention measures non-linear elastic characteristics due to vibration obtained by projecting sound waves onto a measurement object, thereby measuring freshness measurement under storage conditions such as vegetable humidity and temperature, and characteristics with respect to environmental conditions such as humidity, temperature and solar radiation of sound insulation building materials. It can be applied to the measurement and diagnosis of material properties with a wide range of elastic properties such as change measurement, measurement of thermal properties of plastic materials, and aging diagnosis of human skin.

It is a perspective view explaining the characteristic measuring apparatus structure of the elastic body by the nonlinear response of the sound wave of this invention. It is a figure explaining the influence evaluation method by the various factors of the elastic body which displayed the attractor of this invention. It is a top view explaining the measuring method of the present invention. It is a characteristic view which shows the output sound wave from the speaker of this invention. It is a characteristic view explaining extraction of the reflected wave from the output waveform from the actual microphone of the present invention. (A)-(h) is a wave form diagram explaining the reflected wave period extraction combined waveform used in order to display the attractor of this invention. (A)-(h) is a wave form diagram explaining the attractor of this invention.

Explanation of symbols

1. Measurement object (for example, building material board)
DESCRIPTION OF SYMBOLS 2 ... Speaker 3 ... Microphone 4 ... Sound insulation box 5 ... Sound insulation partition 6 ... Oscillator 7 ... Projection sound to measurement object 8 ... Reflection sound from measurement object 9 ... Analog / digital converter 10 ・ ・ PC 11 ・ ・ Phase delay (delay time τ seconds)
12 .... Sound reception signal 13 .... Signal delayed by .tau. Seconds from sound reception signal 14..Horizontal axis (X axis) of signal display Cartesian coordinate screen
15 .. Vertical axis (Y axis) of Cartesian coordinate screen for signal display
16 .... Orbital figure of signal change to display attractor

Claims (5)

An object to be measured for elasticity characteristics;
A speaker that is spaced apart from the object to be measured and outputs sound waves having an audible frequency;
A microphone that collects reflected sound from the measurement object;
Elasticity using sound waves, characterized in that the reflected sound from the microphone is AD-converted, a chaotic non-periodic change figure is displayed on a display device, and the elastic characteristic of the measurement object is measured by non-contact measurement How to measure characteristics.   The sound wave of the audible frequency is alternately output in the form of a pulse, and in addition to the object to be measured, a graphic of chaotic aperiodic change is displayed on the display device using a received sound wave shape obtained by cutting out and reflecting the reflected sound. The method for measuring elastic characteristics using sound waves according to claim 1.   2. The method for measuring elastic characteristics using sound waves according to claim 1, wherein the microphone is coaxially arranged on the front surface of the speaker and cuts out and collects reflected sound from the measurement object.   An XY rectangular coordinate display device is used as the display device, and the elastic characteristic of the measurement object is measured by a change of an attractor drawn by adding the received wave shape and a signal after phase delay processing to the respective coordinates. The method for measuring elastic properties using sound waves according to claim 2.   5. The method for measuring elastic characteristics using sound waves according to claim 4, wherein the phase delay processing is performed for three sample periods.

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