JP4511450B2 - Vacuum magnetic levitation type anti-vibration anechoic box - Google Patents

Description

  The present invention relates to a vacuum magnetic levitation type anti-vibration anechoic box, and in particular, measurement of generated noise power of a low noise type OA device, evaluation of a measuring device such as a noise meter, and various types including hearing and voice. The present invention relates to a vacuum magnetic levitation type anti-vibration anechoic box that can be used for experiments and research.

  In recent years, the sound environment in the world has been increasing year by year (dark) noise levels, both indoors and outdoors. On the other hand, many OA devices including computer peripheral devices are being designed in a direction of calming year by year. In addition, high-output and high-sensitivity microphones and precision sound level meters that are capable of measuring even very low sound pressure levels are being developed and marketed. In order to enable easy measurement and evaluation of these in general offices, etc., they have extremely high sound insulation and sufficient interior silence, and are large soundproof rooms and anechoic rooms. A small soundproof anechoic box is required.

  Conventionally, what is shown in FIG. 9 is known as a soundproof box or a soundproof room. A soundproof room 100 shown in FIG. 9 is used in a recording studio or the like and has a double structure floating structure. In other words, the soundproof room 100 is a double or triple wall made of a material having an appropriate transmission loss (TL (dB)) for the external sound insulation wall 102 or the internal sound insulation wall 104, and when a high level of sound insulation performance is required. The internal sound insulation wall 104 is supported by the vibration insulation rubber 106 and the spring 108 shown in FIG.

  FIG. 11 shows sound insulation of a double wall and its equivalent circuit. Further, FIG. 12 shows the relationship between the frequency and the transmission loss as a theoretical value of the transmission loss (TL) of the double wall.

  On the other hand, as shown in FIG. 13, for magnetic vibration isolation, an attempt has been made to make the turntable 112 of the record player 110 anti-vibration by the repulsive force of the permanent magnet 114.

  The conventional soundproof room 100 employs a double / triple structure, but has the following disadvantages.

  (1) Due to the plate material and the intermediate air layer, a non-negligible sound insulation drop (dip, dip) as shown in FIG. 12 called “resonance transmission” occurs at a plurality of frequencies, and the sound insulation performance is improved to a certain level or more. Can not.

(2) In particular, at the lowest dip frequency, f _rm (Hz), a “total transmission (no sound insulation)” worse than that of the constituent material alone, that is, a passing phenomenon of TL = 0 (dB) occurs. Incidentally, in the triple structure, a plurality of such valleys appear.

(3) Further, the anti-vibration rubber 106 and the spring 108 that support the internal sound insulation wall 104 have the performance of reducing the passage of the solid sound (solid propagation sound = vibration) through the support portion, but the vibration isolation itself The propagation of solid sound cannot be made completely zero because of the restriction of spring constant selection (cannot be made unlimitedly small) that is related to the basic function of supporting and fixing.
In addition, the conventional magnetic isolation has the following inconveniences and problems.
(4) In the one-way vibration isolation as shown in FIG. 13, the vibration (solid sound propagation) energy through the shaft of the turntable or the like remains, so that the propagation cannot be made completely zero.

  (5) Even if vibration isolation can be achieved completely without contact as in the case of a superconducting linear motor car, the noise propagation from the outside will propagate the noise energy from the outside as the entire soundproof anechoic box. It cannot be zero.

  As described above, the present invention has been made in view of the problems of the prior art described above, and by simultaneously blocking the propagation paths of both the solid propagation sound and the air propagation sound, an unprecedented highly quiet space can be obtained. It is aimed to be realized with minor constituent materials.

  In order to achieve the above object, the present invention provides an inner box that is sound-absorbed on the inside, an outer box that covers the periphery of the inner box, a magnet for an inner box that is fixed to the outside of the inner box, and the magnet. And an outer box magnet fixed to the inner side of the outer box with the same poles facing each other, and the inner box has a repulsive force acting between the inner box magnet and the outer box magnet Thus, a vacuum magnetic levitation type anti-vibration anechoic box is formed which is supported in a vibration-proof manner in a non-contact manner with respect to the outer box, and the air in the space between the inner box and the outer box is evacuated. .

  According to the above-described means, the inner box is supported in a vibration-proof manner without contact with the outer box, is not in contact with vibration at all, and the air between the inner box and the outer box is evacuated. The medium itself (air propagation sound) can be removed, and the propagation path of both solid propagation sound and air propagation sound can be cut off almost completely. That is, by removing the acoustic propagation path (for example, air for air sound and vibration-proof material for solid sound) itself, and removing the medium that controls the propagation itself, it is overwhelmingly large with a relatively light material structure. Sound insulation performance can be obtained.

  Further, when configuring the vacuum magnetic levitation type vibration-proof anechoic box, a part of the outer box and the inner box are each formed of a transparent member, and at least a part of the transparent members are opposed to each other. Deploy. In this case, the change and state inside the vibration-proof anechoic box can be observed through the transparent member, and it can be used for various experiments and measurements in research areas other than sound and speech.

  As means for further improving the vibration isolation performance, the current of the electromagnet can be adaptively controlled according to noise and vibration entering from the outside.

  Specifically, at least one of the magnets fixed to the inner box and the outer box is an electromagnet, and a current transmitted to the inner box or noise transmitted to the inner box by adaptive control according to vibration from the outside, Alternatively, control / configuration is performed to minimize vibration energy.

  If such adaptive processing functions under ideal conditions, from the viewpoint of noise control, it is possible to construct conditions just like the interior of an elevator that naturally falls inside a vacuumed tower (elevator wires If the sound insulation of the elevator housing is sufficient, ignoring the transmitted solid sound, the interior will be quiet in the same space as no noise from the outside.

  According to the present invention, an overwhelmingly large sound insulation performance can be obtained with a relatively light material structure. As a result, in a general living room such as an office instead of a large soundproof room or anechoic room, 0 dB-SPL is achieved. It is possible to realize an approaching ultra-quiet space.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a vacuum magnetic levitation type vibration-proof anechoic box showing an embodiment of the present invention. In FIG. 1, a vacuum magnetic levitation type anti-vibration anechoic box 10 has a double structure having an inner box 12 and an outer box 14 covering the periphery of the inner box 12, and has an outer dimension of approximately 250 × 360 × 450 mm. The inner box 12 and the outer box 14 are made of a material having a relatively large surface density, such as a calcium silicate plate, for example. For example, glass wool (abbreviated as GW in the figure) having a thickness of about 25 to 50 mm is attached to the inner side of the inner box 12 as a sound absorption process. Specifically, the anechoic box 10 is provided with a calcium silicate plate having a thickness of about 30 mm and about 20 mm on both sides with a vacuum layer of about 50 mm in between, and inside each calcium silicate plate, It is the structure which affixed glass wool about 50 mm in thickness over the whole surface. In addition, by attaching glass wool having a thickness of about 50 mm over the entire surface of the inner box 12 and the outer box 14 before the air between the inner box 12 and the outer box 14 is evacuated. Even in the state, a certain degree of sound insulation can be improved.

  A plurality of permanent magnets, for example, neodymium magnets 16, are dispersed and fixed as inner box magnets on the outer bottom surface and the outer side surface of the inner box 12 according to the weight of the inner box 12. Further, a plurality of neodymium magnets 18 are dispersed and fixed as outer box magnets so that the same poles, for example, S poles or N poles, face each other and face each other. Yes. Since each of the neodymium magnets 16 and 18 is disposed opposite to each other, the magnetic repulsive force acts between each neodymium magnet 16 and each neodymium magnet 18 as shown in FIG. It has become. That is, the inner box 12 floats from the bottom surface of the outer box 14 and is supported in a vibration-proof manner without contact with the outer box 14. For this reason, fixed propagation sound (vibration) is extremely difficult to be transmitted, and the neodymium magnets 16 and 18 are arranged in a plurality of regions on the bottom surface and the peripheral side surface of the inner box 12 and the outer box 14. Can be stably supported. In place of the neodymium magnets 16 and 18, electromagnets can be used. In this case, the noise transmitted to the inner box 12 can be actively minimized by using one or both of the electromagnets and adaptively controlling the current according to the vibration transmitted from the outside to the outer box 14.

  A pipe 24 connected to the compressor 22 is inserted into the through hole 20 formed in the bottom of the side surface of the outer box 14, and a cock 26 disposed in the middle of the pipe 24 is opened to open the compressor By driving 22, the air in the space 28 between the outer box 14 and the inner box 12 is evacuated, and at least the contained oxygen is kept at a vacuum of about 5% or less. For this reason, it is possible to almost completely block the air sound from propagating into the inner box 12. In addition, since the air in the space 28 is completely removed and becomes a vacuum, if the cock 26 is closed after the evacuation to shut off the air leakage, ultra-quietness is realized in the inner box 12 for a long time. be able to. Furthermore, if a “vibration-proof penetrating duct” designed to sufficiently block vibration and air is passed between the two, acoustic experiments using animals and plants will be possible.

  On the upper side (ceiling surface side) of the inner box 12 and the outer box 14, viewing windows 30 and 32 made of a transparent member, for example, a glass plate or an acrylic plate are provided. For this reason, when it is necessary to observe an internal change or state from the outside, the internal change or normal state can be observed from the viewing windows 30 and 32 without impairing the sound insulation.

  In addition, a hole (not shown) for inserting a test specimen, a specimen, or a microphone 34 is formed on the upper side (ceiling surface side) of the inner box 12 and the outer box 14. In FIG. 3, air-tight opening / closing plates (child doors) 36 and 38 as shown in FIG. 3 are detachably fixed. As shown in FIG. 3, each of the opening and closing plates 36 and 38 is formed in a rectangular shape, and a sufficiently soft thin wire (extremely thin wire) 40 having no vibration propagation such as a power cable or a signal cable is inserted into the center portion. Through-holes (not shown) are formed. The through-hole is subjected to an airtight process such as caulking, and the outside of the airtight double structure lid 42 formed in a substantially cylindrical shape is inserted and fixed. A screw (not shown) is formed on each of the inner tube and the outer tube forming the lid 42, and the inner tube inserted into the outer tube is turned clockwise to be fastened with the outer tube to ensure airtightness. When turned in the opposite direction, the fastening is released. As shown in FIG. 3c, the cable hole at the center of the inner and outer tube bodies of the lid body 42 constituted by two pieces is sealed by caulking after fastening. Each open / close plate 36, 38 is constructed by attaching steel plates to both sides of the calcium silicate plate and attaching glass wool of about 50mm thickness to the inner steel plate to ensure sufficient sound insulation and confidentiality. In order to do so, it is screwed to the anechoic box body through a rubber plate or the like.

  It is estimated that the effective sound insulation NIF (dB) indicating the sound insulation performance of the vacuum magnetic anti-vibration anechoic box 10 having the above-described configuration is approximately expressed by the following equation.

Here, TL ₁ , TL ₂ , A, S, and α (α with an overline bar) are the total transmission loss of the outer box constituent material (average total transmission loss of the entire box) and the inner box configuration, respectively. The total transmission loss of the material, the total sound absorption capacity inside the inner box, the inner surface area, and the average sound absorption coefficient. Further, Δ (dB) is an attenuation amount of acoustic energy due to the vacuum in the intermediate layer portion sandwiched between the inner box 12 and the outer box 14, and there is no medium that transmits sound waves (air sound). ∞. However, since it is considered that there is slight propagation in the residual air and the magnetic vibration isolating portion, it is estimated that it is actually about 20 dB. The actual Δ is considered to depend on the degree of evacuation and the specifications of magnetic vibration isolation. However, it is considered that further attenuation can be secured by increasing the degree and accuracy.

  Table 1 shows the approximate numerical values when the NC curve is digitized for each frequency. Table 2 shows the estimated NIF (dB) when the inner box 12 and the outer box 14 are made of calcium silicate plates. Here is an example. In Table 1, values of NC-10 and below are outside the standard, but are obtained by extrapolation from the standard value for comparison and are described as “equivalent values” to the last. Both are graphed and shown in FIG. In addition, in the calculation, a general office is assumed as the installation environment of the anechoic box, and NC-40 is assumed.

  From the numerical NC curve, the estimated value of NIF (dB) obtained by the vacuum magneto-vibration anechoic box 10 is equal to or more than each band 60 (dB). It becomes approximately 0 (dB-SPL) in the frequency band (63 Hz to 8 kHz), and according to the JIS phone (dB (A)), a negative value far below 0 dB (A) (for example, -10 phone, -15 dB ( A) etc. are expected.

  According to the present embodiment, the inner box 12 is supported in a vibration-proof manner in a non-contact manner with respect to the outer box 14, does not contact at all vibrationally (in terms of solid sound propagation), and the inner box 12 and the outer box 14. Since the air between the two is evacuated, there is no medium through which the sound is transmitted, and the propagation path for both the solid propagation sound and the air propagation sound can be cut off almost completely. As a result, a high level of sound insulation can be realized with a relatively light material (in particular, the inner box 12).

  Specifically, even in a background noise environment of a general office level (50 to 60 phones), the internal background noise is 0 phones, or a very low sound pressure level of less than that, for example, 0 (dB-SPL) or less (NC The noise level can be reduced to a value equivalent to -10).

  In addition, as a material for the inner box 12 and the outer box 14, a light and airtight material such as an acrylic plate or an aluminum plate, and not a glass or steel plate, and a light material having high rigidity, a light material having a relatively small surface density. (In particular, the inner box 12).

  Further, since air may exist inside the inner box 12, the air is circulated into the inner box without transmitting vibration by the above-mentioned “vibration-proof penetration duct” (anti-vibration penetration system), etc. Various experiments and measurements can be performed under conditions close to.

  In addition, if it is necessary to eliminate the signal lines such as the lighting inside the inner box, the power cable for equipment, the signal line such as the microphone cable and the communication line of the related equipment (for example, microphone amplifier or speaker) in terms of vibration isolation, This can be realized by installing a battery or by wireless signal transmission (wireless communication).

  Further, when the inner box 12 is constructed as a large environment where humans can enter it, that is, when the entire system is configured as a “soundproof room”, ducts and piping of various building equipment including air conditioning equipment are included. It is necessary to install between the box (room) 12 and the outer box (room) 14, but this also introduces the “vibration-proof penetration system / technique” that is usually used for the floating structure of recording studios, etc. If sufficient vibration-proof performance and sound-insulation performance are secured, this can be achieved without difficulty.

  Moreover, the inner box 12 can be stably floated inside the outer box 14 by attaching to the inner box 12 and the outer box 14 and selecting the position and strength of each neodymium magnet 16 and 18 as follows.

  First, conditions for the inner box 12 to stably balance in the plane will be described. In this case, the inner box 12 and the outer box 14 are cylindrical, but the planar shape may be rectangular, circular, or any more complicated shape. As the simplest example, for example, a circular cross section (cylindrical shape) is considered as shown in FIG. In this case, the neodymium magnets 16 and 18 are also annular, for example, the inner box 12 has an N pole on the outside, an S pole on the inside, and the outer box 14 has the opposite, and the neodymium magnets 16, 18 are attached to the inner box 12 and the outer box 14, respectively.

  In this state, it is assumed that the balance of the system including the inner box 12, the outer box 14, and the neodymium magnets 16 and 18 is lost for some reason, and the neodymium magnets 16 and 18 partially approach each other. Then, in the neodymium magnets 16 and 18, the distance between the same poles is reduced and the repulsive force is increased. For this reason, force acts on the neodymium magnets 16 and 18 in the direction of pushing back, and as a result, the system returns to the equilibrium state again. In this way, the entire system forms a trough-shaped balance and maintains the equilibrium.

  Further, in the case of a rectangular cross section, as shown in FIG. 6, if the neodymium magnets 16 and 18 are respectively attached so that the same poles face each other at the corners of the inner box 12 and the outer box 14, As well as the overall balance of the system.

  On the other hand, in order to keep the cylindrical inner box 12 vertical without being inclined as a balance within the vertical section, as shown in FIG. It is attached to the upper and lower ends of the box 12 and the outer box 14. In this case, the vertical dimension of the neodymium magnets 16 and 18 needs to be approximately the same as the movement range of the inner box 12, for example, L = 10 mm. The neodymium magnet 18 of the floor portion that supports the weight of the inner box 12 including the specimen in the vertical direction needs to have a strength corresponding to that, but the strength should be within the design dimension L (mm). The magnetic density, the number, etc. of the neodymium magnet 18 may be selected.

  Further, when one or both of the neodymium magnets 16 and 18 are electromagnets and the current of the electromagnets is adaptively controlled to optimize the vibration isolation performance, the system is constructed as follows.

  For example, at least one of the neodymium magnets 16 and 18 is an electromagnet, and the electromagnet is used in accordance with room noise in the installation environment (intrusion noise into the outer box 14) or vibration (solid sound) of the outer box 14 due to this. Control. Hereinafter, an example in which the electromagnet 50 of the outer box 14 is controlled using an FIR (Finite Impulse Response) filter is shown in FIG.

  In FIG. 8, a microphone 52 that collects indoor noise (external noise energy entering the outer box 14) such as a laboratory in which a soundproof anechoic box is placed is arranged outside the outer box 14. A microphone 54 functioning as an error sensor is disposed in the inside. The microphone 52 is connected to the FIR filter 58 via the head amplifier 56, and the microphone 54 is connected to the FIR filter 58 via the head amplifier 60. The FIR filter 58 is connected to the electromagnet 50 of the outer box 14 via the power amplifier 62.

  Here, when the current of the electromagnet 50 is actively controlled via the FIR filter 58 and the power amplifier 62 in accordance with the output of the microphone 52, when a fixed FIR filter is used as the FIR filter 58, the output of the microphone 54 is used. The values of various parameters are set in advance through measurement or the like so that is minimized. On the other hand, when an adaptive FIR filter is used as the FIR filter 58, the parameters are optimally controlled from moment to moment so that the output of the microphone 54 is minimized.

  The microphone 52 and the microphone 54 can be replaced with vibration pickups 64 and 66, respectively, as necessary or to increase the accuracy of adaptation. The vibration pickup 64 is installed on the wall surface or floor surface of the inner box 12, and the vibration pickup 66 is installed on the floor surface of the outer box 14. In this case, when performing posture control to keep the inner box 12 always horizontal, a displacement pickup type is used as the vibration pickup 66, and the electromagnet 50 and the FIR filter 58 of the control system are controlled by this output. To do.

  In this way, at least one of the neodymium magnets 16 and 18 is the electromagnet 50, and the current flowing through the electromagnet 50 is fixedly or actively controlled to vibrate the inner box 12 or the noise in the inner box internal space. By minimizing the noise, it is possible to enhance the performance of blocking noise entering the inner box 12 to the limit.

  That is, with respect to noise energy (solid sound / vibration) that is slightly propagated to the inner box 12 via magnetic levitation, the amount of noise energy propagation is minimized by adaptively controlling the current flowing through the electromagnet 50 according to the noise. Therefore, it can be actively controlled. At this time, a fixed or adaptive FIR filter 58 is used for control. In the latter case, a vibration pickup 66 attached to the surface of the inner box 12 or a microphone 54 installed in the inner box is used as an error sensor. Use. If the control is independent for each electromagnet 50 and a displacement control type vibration sensor is used as the error sensor, it is possible to perform posture control such as keeping the inner box 12 horizontal regardless of the position deviation of the specimen.

1 is a cross-sectional view of a vacuum magnetic levitation type vibration-proof anechoic box showing an embodiment of the present invention. A side view of a neodymium magnet. (A) Front view of opening / closing plate, (b) Side view of opening / closing plate, (c) Front view of lid. NC curve characteristic diagram. The plane sectional view for explaining the balance in a circular section. The plane sectional view for explaining the balance in a rectangular section. Sectional drawing for demonstrating the balance in an upright section. Sectional drawing of the vacuum magnetic levitation type vibration-proof anechoic box which shows the other Example of this invention. Sectional drawing of the conventional soundproof room. The figure which shows the example of a vibration isolator. The figure which shows the sound insulation of a double wall, and an equivalent circuit. The characteristic figure of the TL theoretical value of the double wall which shows the relationship between a frequency and transmission loss. The side view of a magnetic levitation type record player.

Explanation of symbols

10 Vacuum magnetic vibration-proof anechoic box 12 Inner box 14 Outer box 16, 18 Neodymium magnet 22 Compressor 30, 32 Viewing window 36, 38 Opening / closing plate

Claims (3)

An inner box that is sound-absorbed on the inner side, an outer box that covers the periphery of the inner box, a magnet for an inner box that is fixed to the outer side of the inner box, and the same poles as the magnet are opposed to each other. A magnet for the outer box fixed to the inner side of the inner box, and the inner box is prevented from contacting the outer box in a non-contact manner by a repulsive force acting between the inner box magnet and the outer box magnet. The air in the space between the inner box and the outer box is evacuated , the inner box magnet is fixed to the bottom and side surfaces of the outer side of the inner box, and the outer box magnet is The magnet is fixed to the bottom and side surfaces of the inner side of the outer box, and at least one of the magnets fixed to the inner box and the outer box is composed of an electromagnet, and the electromagnet controls the electromagnet. And the control means includes a first microphone disposed in the inner box and the outer box. The electromagnet is connected to a second microphone arranged at the position of the electromagnet so as to minimize noise or vibration energy transmitted to the inner box based on the output of the first microphone and the output of the second microphone. Vacuum magnetic levitation type anti-vibration anechoic box controlled by current .  2. The vacuum magnetic levitation type vibration-proof anechoic box according to claim 1, wherein a part of each of the outer box and the inner box is formed of a transparent member, and each of the transparent members is disposed so as to face each other. A vacuum magnetic levitation type anti-vibration anechoic box. In the vacuum magnetic levitation type anti-vibration anechoic box according to claim 1, instead of the first microphone, a first vibration pickup installed in the inner box is used, and instead of the second microphone, A vacuum magnetic levitation type vibration -proof anechoic box using a second vibration pickup installed in the outer box.

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