JP2005274509A - Sound measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sound measuring device capable of measuring a large sound without being almost influenced by temperature, humidity, vibration, electricity, magnetism or the like. <P>SOLUTION: This device comprises a low-temperature side heat exchanger 20 provided on the downstream side of a sound input direction, a high-temperature side heat exchanger 22 provided on the upstream side of the sound input direction, and a stack 21 having a number of conduits extending through in the sound input direction, which is provided between the heat exchangers 20 and 22. In this device, thermal energy is transferred in a direction opposite to the input of sound energy, and the physical characteristic of the sound is measured based on the temperature difference between the heat exchangers 20 and 22 which is caused thereby. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sound measuring apparatus for measuring noise and the like, and more specifically, a sound measuring apparatus for measuring physical characteristics of sound such as sound pressure level using a thermoacoustic effect. It is about.

  As a device for measuring a sound pressure level, a sound measuring device or the like is conventionally known. As described in Non-Patent Document 1, this sound measuring apparatus includes a microphone for catching a sound to be measured, and various circuits such as a preamplifier, a frequency correction circuit, and an effective value leveling circuit. Therefore, the sound caught by the microphone is amplified by a preamplifier, and the sound pressure level and the like can be output by performing frequency correction and the like.

By the way, as a microphone used in such a sound measuring apparatus, an electrostatic microphone is often used. This electrostatic microphone is equipped with a vibrating membrane and a fixed electrode, detects the change in capacitance stored between the fixed electrode due to the vibration of sound, and outputs this as an electrical signal It is.
“Manual for Low Frequency Sound Measurement Method” (October, 2000) Atmospheric Environment Bureau, Ministry of the Environment

  However, since such an electrostatic microphone is accompanied by a change in the capacitance stored between the diaphragm and the fixed electrode, a constant temperature environment is used so that the capacitance does not change. (For example, −10 ° C. to + 50 ° C.) or in a certain humidity environment (for example, 90% or less), and in a place where there is no adverse influence such as vibration, electricity, magnetism, etc. Must be used. Furthermore, in such an electrostatic microphone, the measurable level range is limited to 60 to 120 dB due to the gap width relationship between the vibrating membrane and the fixed electrode, and damage to the vibrating membrane occurs when attempting to measure louder sound than this. There was a problem that would cause.

  Therefore, the present invention has been made paying attention to the above problems, and an object of the present invention is to provide a sound measuring device that is not easily affected by temperature, humidity, vibration, electricity, magnetism, and the like and that can measure a loud sound. To do.

  That is, in order to solve the above problems, the present invention provides a low temperature side heat exchanger provided downstream in the sound input direction, a high temperature side heat exchanger provided upstream in the sound input direction, and the low temperature The low-temperature side heat exchanger generated on the basis of the sound input, comprising a stack having a plurality of conduction paths sandwiched between the side heat exchanger and the high-temperature side heat exchanger and penetrating in the sound input direction. And measuring means for measuring the physical characteristics of the input sound based on the temperature difference between the high-temperature side heat exchanger and the high-temperature side heat exchanger.

  If comprised in this way, the "principle of a thermoacoustic effect" which transfers a thermal energy in the opposite direction to the input sound energy can be utilized, and the low temperature side heat exchanger and high temperature side heat exchanger which were produced by this can be used. The physical characteristics of sound can be measured using the temperature difference between For this reason, it is not greatly affected by heat, humidity, vibration, electricity, magnetism, etc. as in the past, and even when large sound energy is input, it is ensured without causing damage to the diaphragm. The physical characteristics of sound can be measured.

  Further, such a stack having a meandering conduction path is used.

  If comprised in this way, since the conduction path meanders, the contact area of a working fluid and a stack will increase, and more heat exchange can be performed. As a result, the temperature difference between the low temperature side heat exchanger and the high temperature side heat exchanger becomes large, and the physical characteristics of sound can be reliably measured.

  Furthermore, a cylindrical body that covers the low-temperature side heat exchanger and the high-temperature side heat exchanger and has an opening that opens in the sound input direction is provided.

  If comprised in this way, since the input direction of a sound can be restrict | limited by a cylindrical body, it becomes possible to give directionality to sensing. In addition, if the cylindrical body is configured to be long, the cylindrical body can prevent direct sunlight from being irradiated to the low temperature side heat exchanger, the high temperature side heat exchanger, etc. There will be no occurrence of temperature unevenness in each heat exchanger.

  In addition, a sound collection unit is provided for collecting sound to be measured toward the high temperature side heat exchanger.

  If configured in this way, the temperature difference between the low-temperature side heat exchanger and the high-temperature side heat exchanger can be increased by the large collected sound, and the physical characteristics of sound can be measured more reliably by this temperature difference. Will be able to. In addition, as such a sound collection part, what has a focus like a parabona antenna etc. is used, for example.

  In addition, when an electrical signal is output based on the temperature difference between the low temperature side heat exchanger and the high temperature side heat exchanger, a thermoelectric converter is connected to the low temperature side heat exchanger or the high temperature side heat exchanger, and this thermoelectric conversion is performed. The physical characteristics of sound are measured based on the electrical signal output from the instrument.

  With this configuration, since an electrical signal is output from the thermoelectric converter, a preamplifier, a frequency correction circuit, an effective value leveling circuit, an indicator, and the like used in a conventional sound measurement device are used. If a simple circuit is connected, the sound measuring device can be easily configured.

  Moreover, when outputting an electrical signal based on the temperature difference between the low temperature side heat exchanger and the high temperature side heat exchanger, the low temperature side heat exchanger and the high temperature side heat exchanger are made of different types of metal materials, The physical characteristics of sound are measured by electrical signals generated by the temperature difference between the low temperature side heat exchanger and the high temperature side heat exchanger.

  If comprised in this way, the Seebeck effect that an electromotive force is generated by a temperature difference between different kinds of metals can be used, and an electric signal can be output without using a separate new thermoelectric converter. It becomes like this. As a result, a relatively inexpensive sound measuring device can be obtained.

  In the present invention, the low temperature side heat exchanger provided downstream in the sound input direction, the high temperature side heat exchanger provided upstream in the sound input direction, the low temperature side heat exchanger, and the high temperature side heat exchange. Temperature of the low temperature side heat exchanger and the high temperature side heat exchanger generated on the basis of the sound input. Since the measurement means for measuring the physical characteristics of the input sound based on the difference is provided, the temperature difference between the low temperature side heat exchanger and the high temperature side heat exchanger caused by the thermoacoustic effect is used. The physical characteristics of sound can be measured. For this reason, unlike conventional sound measurement devices using microphones, they are not greatly affected by heat, humidity, vibration, electricity, magnetism, etc., and even when large sound energy is input. It is possible to measure the physical characteristics of sound such as sound pressure level.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a sound sensor 2 in a sound measurement device 1 according to the present embodiment. FIG. 2 is a functional block diagram of the sound measurement device 1 including the sound sensor 2. is there. 3 to 6 show the structure of the stack 21, the sound sensor 2, and the sound measuring device 1 used in other embodiments.

  The sound measurement device 1 in this embodiment includes a sound sensor 2 that uses a thermoacoustic effect and a measurement device that measures the physical characteristics of the sound input to the sound sensor 2.

  Among these, the sound sensor 2 includes a low-frequency heat exchanger 20 provided on the downstream side with respect to the traveling direction of the sound energy, and a high-temperature side heat exchanger 22 provided on the upstream side with respect to the traveling direction of the sound energy. The stack 21 is provided so as to be in close contact with the bass-side heat exchanger 20 and the high-temperature side heat exchanger 22.

  The stack 21 has a large number of conduction paths 21a penetrating in the traveling direction of sound energy, and is made of a porous ceramic having a relatively low specific heat. Further, the bass heat exchanger 20 provided on the downstream side in the sound input direction in the stack 21 is formed of a metal material having a relatively high thermal conductivity such as copper, and the inside of the thin metal material. Is provided with an opening 20 a corresponding to the conduction path 21 a of the stack 21. Similarly, the high-temperature side heat exchanger 22 provided on the upstream side in the sound input direction in the stack 21 is similarly formed of a metal material having a relatively high thermal conductivity, such as copper, and a thin metal material. Is provided with an opening 22a corresponding to the conduction path 21a of the stack 21. The low-frequency heat exchanger 20, the openings 20a and 22a of the high-temperature side heat exchanger 22 and the conduction path 21a of the stack 21 are linearly penetrated, and the low-temperature side heat exchanger 20 generated by the thermoacoustic effect and the high temperature Based on the temperature difference from the side heat exchanger 22, the physical characteristics of sound such as the sound pressure level are measured.

  Next, the principle of this thermoacoustic effect will be described with reference to FIG.

  First, in a working fluid such as air, a sound sensor 2 including a stack 21, a low-frequency heat exchanger 20, and a high-temperature heat exchanger 22 is provided. When sound is input to the sound sensor 2, the sound energy is converted to high-temperature heat. It is transferred from the exchanger 22 side through the stack 21 to the bass heat exchanger 20 side. Then, the working fluid existing in the conduction path 21a of the stack 21 starts to fluctuate due to the vibration of the sound, and at that time, the thermal energy stored in the minute air mass due to the adiabatic expansion and contraction of the minute air mass is accumulated in the stack. 21 is accumulated. Then, the heat energy is transferred in the direction opposite to the sound energy transfer direction according to the law of conservation of energy, and as a result, the high temperature side heat exchanger 22 is heated, and the low temperature side heat exchanger 20 and the high temperature side heat exchanger 22 are heated. A temperature difference will occur between the two.

  A thermoelectric converter 24 is connected to the low temperature side heat exchanger 20 and the high temperature side heat exchanger 22 of the sound sensor 2 using the principle of the thermoacoustic effect. The thermoelectric converter 24 generates an electromotive force corresponding to a temperature difference generated between the low-frequency heat exchanger 20 and the high-temperature heat exchanger 22. For example, a semiconductor element using the Seebeck effect is used. Used. As a semiconductor element using the Seebeck effect, a bismuth-tellurium-based semiconductor element or a silicon-germanium-based semiconductor element, which is currently considered to be most efficient, may be used. Then, these elements are connected to the low-frequency side heat exchanger 20 and the high-temperature side heat exchanger 22 to generate electromotive forces corresponding to the respective temperature differences. The thermoelectric converter 24 may be configured by an electric circuit that can detect a weak electric signal when the electric signals from the low temperature side heat exchanger 20 and the high temperature side heat exchanger 22 are weak. .

  A measuring device as shown in the block diagram of FIG. 2 is connected to the thermoelectric converter 24. This measuring apparatus includes a preamplifier 30, a frequency correction circuit 31, an effective value leveling circuit 32, an indicator 33, and the like.

  Among these, the preamplifier 30 amplifies the electric signal generated by the electromotive force output from the thermoelectric converter 24 to a certain level.

  In addition, the frequency correction circuit 31 performs correction processing such as weighting of frequencies corresponding to human hearing when the electrical signal amplified by the preamplifier 30 is converted into a sound pressure level. When listening to sounds by human hearing, high and low sounds are felt at different sound levels even at the same sound pressure level, for example, high sounds tend to be felt as loud sounds. For this reason, in order to cope with human hearing, for example, frequency correction processing such as reducing the weighting in the low-pitched portion is performed. In general, the sound pressure level corrected as described above is referred to as an A characteristic sound pressure level, and other than this, correction according to B, C, D, E, F characteristics, etc. is performed according to the application. Do.

  The effective value leveling circuit 32 converts the frequency corrected by the frequency correction circuit 31 into a physical quantity for output to the indicator 33. The effective value leveling circuit 32 includes an effective value detection circuit 32a, a dynamic characteristic circuit 32b, and a logarithmic operation circuit 32c, and the effective value detection circuit 32a includes an effective value of frequency by a square circuit or the like. Calculate. Further, the dynamic characteristic circuit 32b has dynamic characteristics for operating the indicator 33 early, dynamic characteristics for operating the indicator 33 late, and the like. For example, the fast dynamic characteristic is set to 125 ms or the like, while the slow dynamic characteristic is set to 1 s or the like. The logarithmic arithmetic circuit 32c converts the effective value calculated in this way into a decibel value as a sound pressure level.

  The indicator 33 is composed of an analog meter, a digital meter, or the like, and displays the decibel value calculated by the effective value leveling circuit 32.

  Such a preamplifier 30, a frequency correction circuit 31, an effective value leveling circuit 32, an indicator 33, and the like are already present in this way because they are generally used in a sound measuring apparatus using a microphone currently on the market. Circuits can be used.

  Next, an operation when measuring the sound measuring apparatus 1 configured as described above will be described.

  First, when the directivity direction of the sound sensor 2 is directed to the sound source, the sound energy emitted from the sound source is input into the sound sensor 2 and transferred from the high temperature side heat exchanger 22 into the stack 21. When the sound energy is transferred into the stack 21, the minute air mass in the stack 21 starts to vibrate due to the vibration of the sound, and adiabatic expansion and contraction are repeated due to the vibration. At that time, the heat stored in the minute air mass is accumulated on the inner wall of the stack 21, and according to the law of energy conservation, the heat energy is in the direction opposite to the sound energy transfer direction. It is transferred to. As a result, a temperature difference is generated between the low-frequency heat exchanger and the high-temperature heat exchanger 22, and an electrical signal is output from the thermoelectric converter 24 due to this temperature difference. This electric signal is amplified by the preamplifier 30 of the measuring device 3 and then corrected by a frequency correction circuit 31 such as frequency weighting processing corresponding to various characteristics such as the A characteristic to the F characteristic to obtain an effective value. It is made effective by the level circuit. Then, the effective value is converted into a decibel value by the logarithmic operation circuit 32c of the effective value level circuit, and this value is output to the indicator 33.

  As described above, according to the above embodiment, the physical characteristics of sound are measured from the temperature difference generated between the low-frequency heat exchanger 20 and the high-temperature heat exchanger 22 using the principle of the thermoacoustic effect. As a result, it does not have to be used in a temperature or humidity environment that is limited to a very narrow range as in the past, and it is weak against vibration, electricity, and magnetism. Also disappear. Further, even when a very loud sound is input, the vibration membrane is not damaged as in the conventional case.

  In the above-described embodiment, the stack 21 having the linear conduction path 21 a is used as the sound sensor 2. In such a stack 21, the low-frequency heat exchanger 20 and the high-temperature heat exchanger 22 are connected. There may be no large temperature difference between them. In this case, a stack 210 as shown in FIG. 3 may be used. The stack 210 shown in FIG. 3 is configured by laying microspherical ceramics or the like, thereby forming a meandering conduction path 210a. By providing such a meandering conduction path 210a, the contact area between the working fluid and the inner wall of the stack 210 can be increased, so that a larger heat exchange is possible and the temperature at both ends of the stack 210 is increased. The difference can be increased. The configuration of the stack having meandering conduction paths is not limited to a configuration in which microspherical ceramics are spread, and various configurations can be used.

  Moreover, in the said embodiment, as shown in FIG. 1, what used the low frequency side heat exchanger 20 and the high temperature side heat exchanger 22 to expose is used, but as shown in FIG. You may make it cover with the cylindrical body 23 which has 23a. The cylindrical body 23 is provided with the low-frequency heat exchanger 20, the high-temperature heat exchanger 22, and the stack 21 inside, and is protruded from the low-frequency heat exchanger 20 and the high-temperature heat exchanger 22. A flange 23b is provided. If comprised in this way, the directivity of the axial direction of the cylindrical body 23 can be given, and the sound of a measuring object can be specified and it can measure now reliably. Further, since the flange portion 23b is provided, it is possible to prevent the low temperature side heat exchanger 20, the high temperature side heat exchanger 22 and the like from being irradiated with direct sunlight, and each heat exchanger by irradiation of direct sunlight. It is possible to prevent erroneous measurement by preventing occurrence of temperature unevenness.

  Further, in the above embodiment, the direct sound emitted from the sound source is measured. However, a parabona antenna-like sound collector 4 as shown in FIG. 5 is provided, and the sound is collected by the sound collector 4. Sound may be measured. In this case, the high temperature side heat exchanger 22 is provided in the direction in which the reflected sound from the sound collector 4 is input, and the sound pressure level greatly amplified by the sound collector 4 is returned to the original sound pressure level. For example, a correction circuit is provided. If comprised in this way, the temperature difference in the both ends of the stack 21 can be enlarged with a big sound pressure, and a sound pressure level can be reliably measured by detecting the big electric signal based on this big temperature difference. become able to. Note that the sound collector 4 is not limited to the shape of the parabona antenna, but a megaphone or the like may be used and provided on the high temperature side heat exchanger 22 side.

  Moreover, in the said embodiment, when outputting an electrical signal based on the temperature difference of a low temperature side heat exchanger and a high temperature side heat exchanger, a thermoelectric converter is attached to this low temperature side heat exchanger or a high temperature side heat exchanger. Since it is connected and the physical characteristics of sound are measured based on the electrical signal output from this thermoelectric converter, the preamplifier, frequency correction circuit, and effective value level used in conventional sound measurement devices are used. If a circuit such as a circuit or an indicator is connected, the sound measuring device can be easily configured.

  Moreover, in the said embodiment, although the electric signal based on a temperature difference is output by the thermoelectric conversion element, the structure as shown in FIG. 6 can also be used. FIG. 6 shows that the bass-side heat exchanger 20 and the high-temperature side heat exchanger 22 are formed of different types of metal materials, and the electricity generated from the bass-side heat exchanger 20 and the high-temperature side heat exchanger 22 by the Seebeck effect. A signal (electromotive force) is output. As this metal material, for example, a combination of copper and constantan (copper and nickel alloy) can be considered. By doing so, it is possible to reduce the cost without using a relatively expensive thermoelectric conversion element such as a semiconductor. Can be configured.

The enlarged view of the sound sensor vicinity of the sound measuring device in one embodiment of this invention Functional block diagram of the sound measurement device in the same form Schematic cross-sectional view of the stack in the second embodiment Schematic cross-sectional view of a sound sensor according to the third embodiment The state diagram which attached the sound collector to the sound sensor in the fourth embodiment Schematic of the sound measurement device in the fifth embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Sound measuring device 2 ... Sound sensor 3 ... Measuring device 4 ... Sound collector 20 ... Low temperature side heat exchanger 20a ... Opening 21 ... Stack 21a ... Conduction path 210 ... Stack 210a ... Conduction path 22 ... High temperature side heat exchanger 22a ... Opening part 23 ... Cylindrical body 23a ... Opening part 23b ... Saddle 24 ...・ Thermoelectric converter

Claims (6)

  Sandwiched between a low temperature side heat exchanger provided downstream in the sound input direction, a high temperature side heat exchanger provided upstream in the sound input direction, the low temperature side heat exchanger and the high temperature side heat exchanger And a stack having a large number of conduction paths that penetrate in the sound input direction, and based on a temperature difference between the low temperature side heat exchanger and the high temperature side heat exchanger generated based on the sound input. A sound measuring apparatus comprising a measuring means for measuring a physical characteristic of the input sound.   The sound measuring device according to claim 1, wherein the conductive path of the stack is a meandering conductive path.   The sound measuring device according to claim 1, further comprising a cylindrical body that covers the low-temperature side heat exchanger and the high-temperature side heat exchanger and has an opening that opens in the sound input direction.   The sound measuring device according to claim 1, further comprising a sound collecting unit that collects sound to be measured in the high temperature side heat exchanger.   The measuring means includes a thermoelectric converter that outputs an electric signal based on a temperature difference between the low temperature side heat exchanger and the high temperature side heat exchanger, and the physical characteristics of sound based on the electric signal from the thermoelectric converter The sound measuring device according to claim 1, wherein   The low-temperature side heat exchanger and the high-temperature side heat exchanger are made of different kinds of metal materials, and the measuring means has a low-temperature side heat according to a temperature difference between the low-temperature side heat exchanger and the high-temperature side heat exchanger. The sound measuring device according to claim 1, wherein the physical characteristics of sound are measured by an electric signal generated from the exchanger and the high temperature side heat exchanger.

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