JP2015228704A - Tube, bass reflex port, and acoustic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide technical means for reducing abnormal noise generated from a tube such as a bass reflex port.SOLUTION: A bass reflex port 20 is a hollow and substantially cylindrical tube, which can be sectioned into a straight part 22 having a constant cross-sectional area, and flare parts 24 and 25 on both end sides thereof. The flare part 24 has such a shape as a portion where the cross-sectional area spreads gradually from near a boundary between the straight part 22 and the flare part 24 toward an opening edge 28. An inner wall of the flare part 24 smoothly waves in an inner peripheral direction of the inner wall.

Description

  The present invention relates to an acoustic device such as a tubular body, a bass reflex port, and a bass reflex speaker.

  There is an acoustic device such as a bass reflex speaker that actively uses the sound from the back of the speaker unit to enhance bass (for example, Patent Document 1). An acoustic device such as a bass reflex speaker includes a speaker unit and a bass reflex port in an enclosure (housing) of the acoustic device. The bass reflex port is formed by a tube body having both ends open and one open end fixed to an opening provided in the speaker enclosure. In this acoustic apparatus, gas outside the enclosure is sucked into the enclosure via the bass reflex port, and gas inside the enclosure is discharged outside the enclosure via the bass reflex port.

  FIG. 7 is a cross-sectional view showing a structure of a bass reflex port portion of an acoustic apparatus having a conventional bass reflex port. As shown in FIG. 7A, the cross-sectional shape of the conventional bass reflex port 20A is constant from one end to the other end of the bass reflex port 20A, and the inner wall of the bass reflex port 20A is orthogonal to the baffle surface. In the acoustic device having the bass reflex port 20A having this shape, an abnormal noise (so-called wind noise) resulting from the suction and discharge of gas in the bass reflex port 20A is generated from the bass reflex port 20A. Therefore, conventionally, as shown in FIG. 7B, the shape near the both ends of the bass reflex port 20B has a gas flow path through the bass reflex port 20B, that is, a space surrounded by the inner wall of the bass reflex port 20B. The flare shape that gradually spreads radially from the center side of the port 20B toward the both ends reduces the abnormal noise generated from the bass reflex port 20B.

JP 2012-161109 A

  However, when the signal level supplied to the speaker unit is increased to increase the sound pressure of the sound wave supplied to the bass reflex port, there is a problem that abnormal sound is generated from the bass reflex port even if both ends of the bass reflex port have a flare shape.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide technical means for reducing abnormal noise generated from a tubular body such as a bass reflex port.

  The present invention is a tubular body forming a gas flow path, and gradually expands as the area of the cross section perpendicular to the tubular axis of the space surrounded by the inner wall of the tubular body approaches the open end of the tubular body, Provided is a tubular body characterized in that an inner wall in the vicinity of an opening end is smoothly waved in the circumferential direction.

  In the tubular body of the present invention, the inner wall near the opening end smoothly undulates in the circumferential direction. Therefore, the shape of the inner wall near the opening end as viewed from the tube axis is a part of the inner wall protruding in the direction away from the tube axis. And the inner wall falls in the tube axis direction, and the portion is continuously repeated along the circumferential direction. Although details will be described later, since such a configuration is adopted, it is possible to reduce the occurrence of noise due to the flow of gas into and out of the tube through the tube of the present invention.

It is sectional drawing which shows the structure of the audio equipment 1 which is one Embodiment of this invention. FIG. 4 is a perspective view and a front view of the flare portion 24 of the bass reflex port 20 viewed from the inside of the enclosure 10 of the acoustic device 1. It is a figure which shows the result of having simulated the magnitude | size of the disorder | damage | failure of a gas flow about the conventional bass reflex port which made flare shape the both ends vicinity of a bass reflex port. 3 is a perspective view showing a gas flow in the vicinity of an opening end 28 of a bass reflex port 20 of the acoustic device 1. FIG. It is a figure explaining the gas flow in the inner wall near the opening end 28B of the conventional bass reflex port 20B. It is a figure explaining the gas flow in the inner wall near the opening end 28 of the bass reflex port 20 of the acoustic apparatus 1. It is sectional drawing which shows the structure of the bass reflex port part of the conventional audio equipment.

Embodiments of the present invention will be described below with reference to the drawings.
<Embodiment>
FIG. 1 is a cross-sectional view showing a configuration of an acoustic device 1 according to an embodiment of the present invention. As shown in FIG. 1, the acoustic device 1 includes an enclosure 10, a speaker unit SP, and a bass reflex port 20. The bass reflex port 20 and the enclosure 10 constitute a Helmholtz resonator having a resonance frequency near the lower limit frequency of the band where the sound pressure is flat in the output characteristics of the acoustic device 1.

  The enclosure 10 is a rectangular parallelepiped surrounded by six surfaces, and two openings 18 and 21 are provided in the front surface 11 that functions as a baffle surface among the six surfaces surrounding the enclosure 10. A speaker unit SP is provided in the opening 18.

  The bass reflex port 20 is a hollow, substantially cylindrical tube body, and the cross-sectional area (the area of the cross section perpendicular to the tube axis of the space surrounded by the inner wall of the bass reflex port 20) is constant in the tube axis direction. And the flare portions 24 and 25 at both ends thereof. The flare portion 25 has a flare shape in which the cross-sectional area gradually increases from the vicinity of the boundary between the straight portion 22 and the flare portion 25 toward the opening end 29. The opening end 29 on the flare portion 25 side of the bass reflex port 20 is fixed to the opening portion 21 of the front surface 11 that functions as a baffle surface.

  2A is a perspective view of the flare portion 24 of the bass reflex port 20 viewed from the inside of the enclosure 10 of the acoustic device 1, and FIG. 2B is a front view of the opening end 28 on the flare portion 24 side. It is. As shown in FIGS. 2 (a) and 2 (b), the flare portion 24 has a shape like a funnel-shaped corolla such as a convolvulus or sweet potato flower (hereinafter simply referred to as a corolla shape). More specifically, the flare portion 24 has a cross-sectional area that gradually increases from the vicinity of the boundary between the straight portion 22 and the flare portion 24 toward the opening end 28, and the curvature of the inner wall is increased within the tube axis of the flare portion 24. The shape is repeatedly increased or decreased along the circumferential direction. In addition, a portion where the center of curvature of the inner wall in the cross section perpendicular to the tube axis in the vicinity of the open end 28 is located on the tube axis side when viewed from the inner wall, and the side opposite to the tube axis when the center of curvature of the inner wall is viewed from the inner wall And the portion located at is repeated along the inner circumferential direction of the inner wall. In other words, when the inner wall is viewed from the tube axis in a cross section perpendicular to the tube axis in the vicinity of the opening end 28, the inner wall protrudes in a direction away from the tube axis and is convex, and the inner wall falls in the tube axis direction. The concave portion is repeated along the inner circumferential direction of the inner wall. Further, as described above, when the inner wall is viewed from the tube axis, the curvature along the inner circumferential direction of the inner wall of the portion where the inner wall is convex is a positive curvature, and the inner wall is concave. If the curvature along the inner circumferential direction of the inner wall of the part is a negative curvature, the curvature along the inner circumferential direction of the inner wall can be expressed as a repetition of a positive curvature and a negative curvature. it can. Note that the value of the curvature of the inner wall along the inner circumferential direction is determined by simulation or the like for each dimension of the bass reflex port 20.

The flare portions 24 and 25 may be manufactured integrally with the straight portion 22, or separated from the straight portion 22 at the time of manufacture and fixed to the straight portion 22 after manufacture. May be.
The above is the structure of the acoustic device 1.

  FIG. 3 is a longitudinal sectional view showing the result of simulating the magnitude of turbulence (vortex) in the gas flow for a conventional bass reflex port. According to the simulation results shown in FIG. 3, gas flow turbulence (vortex) occurs in a wide range in the vicinity of the outer end of the bass reflex port (open end facing the outside of the enclosure). At the inner end (open end located inside the enclosure), the turbulence (vortex) of the gas flow is generated in a narrow range (locally).

  Here, the gas flow on the inner wall near the opening end 28B (inner end) of the conventional bass reflex port 20B shown in FIG. 7B will be described in detail with reference to FIG. 5A is a cross-sectional view perpendicular to the tube axis at the open end 28B, FIG. 5B is a cross-sectional view taken along the line CC ′ in FIG. 5A, and FIG. FIG. 5A is a cross-sectional view taken along the line DD ′ in FIG. 5A, and FIG. 5D is a cross-sectional view taken along the line CC ′ in FIG. 5A when the left inner wall in FIG. FIG.

  As shown in FIG. 5A, the cross section of the inner wall at the open end 28B of the conventional bass reflex port 20B is circular. 5 (b) is a plane including the tube axis of the bass reflex port 20B shown in FIG. 5 (a), and is a longitudinal section obtained by cutting the bass reflex port 20B along the plane including the positions φ1 and φ7 in the inner circumferential direction of the opening end 28B. The surface structure is shown. As shown in FIG. 5B, when gas flows from the inside of the bass reflex port 20B to the outside of the bass reflex port 20B (inside the enclosure), the gas near the inner wall near the opening end 28B of the bass reflex port 20B flows along the inner wall. . At this time, in the vicinity of the opening end 28B, since the flow area becomes wider toward the downstream of the flow, a reverse pressure gradient is formed in which the downstream pressure increases. The gas flow in the vicinity of the inner wall in which the reverse pressure gradient is formed loses energy due to friction with the inner wall, overcomes the pressure and becomes difficult to flow downstream, and is separated from the inner wall of the bass reflex port 20B. Then, a reverse flow is generated in the vicinity of the inner wall downstream from the position where the gas flow is separated from the inner wall, resulting in a turbulent flow (vortex). The position where the gas flow separates from the inner wall is determined by various conditions such as the degree of expansion of the basin along the downstream direction. In FIG. 5B, a region 52B in which the gas flow separates from the inner wall of the bass reflex port 20B and becomes a turbulent flow (vortex) at the position L0 in the tube axis direction of the bass reflex port 20B.

  FIG. 5 (c) is a plane including the tube axis of the bass reflex port 20B shown in FIG. 5 (a), and is a longitudinal section obtained by cutting the bass reflex port 20B along the plane including the positions φ0 and φ6 in the inner circumferential direction of the opening end 28B. The surface structure is shown. Since the open end 28B has a circular cross section, the cross section shown in FIG. 5C is the same as the cross section shown in FIG. Therefore, in FIG. 5C as well, as in FIG. 5B, the gas flow separates from the inner wall of the bass reflex port 20B at the position L0 in the tube axis direction of the bass reflex port 20B, resulting in a turbulent flow (vortex). Region 52B occurs.

  In FIG. 5D, positions φ1 to φ7 corresponding to the positions φ1 to φ7 in the inner peripheral direction of FIG. 5A are shown on the left side of the C-C ′ line. Since the cross section of the opening end 28B is circular, the cross section at the positions φ1 to φ7 in the inner circumferential direction is the same as in FIGS. 5B and 5C, and the turbulent flow (vortex) at the positions φ1 to φ7 in the inner circumferential direction The region 52B is generated at the same position L0 in the tube axis direction of the bass reflex port 20B. That is, even in the entire area in the inner circumferential direction, in the conventional bass reflex port 20B, the region that becomes a turbulent flow (vortex) is locally distributed in a narrow range in the tube axis direction.

  In the region where the turbulence of gas flow (vortex) occurs in a narrow range, the turbulence of gas flow (vortex) with almost the same phase at the same time occurs at the same time. The magnitude (strength) of the flow turbulence (vortex) is increasing. Thereby, the tube resonance of the bass reflex port is strongly excited, and as a result, a large abnormal noise is generated from the bass reflex port. Therefore, if it is possible to prevent the turbulence (vortex) of the gas flow from being generated locally, the excitation of the bass resonance port tube resonance can be suppressed, and as a result, abnormal noise can be reduced. Therefore, in the acoustic device 1 according to the present embodiment, the shape in the vicinity of the inner end of the bass reflex port 20 (the opening end located inside the enclosure 10) is a corolla shape.

  Next, the gas flow in the vicinity of the opening end 28 of the bass reflex port 20 of the acoustic device 1 according to the present embodiment will be described. When a driving signal is supplied to the speaker unit SP of the audio device 1 to operate the speaker unit SP, the gas on the back surface of the speaker unit SP vibrates, and the gas moves into and out of the enclosure 10 through the bass reflex port 20. FIG. 4 is a perspective view showing the gas flow in the vicinity of the opening end 28 of the bass reflex port 20 when the gas inside the bass reflex port 20 is sucked into the enclosure 10. As shown in FIG. 4, the gas in the vicinity of the opening end 28 of the bass reflex port 20 flows along the inner wall having a corolla shape.

  Here, the gas flow in the vicinity of the inner wall in the vicinity of the opening end 28 of the bass reflex port 20 according to the present embodiment will be described in detail with reference to FIG. 6A is a cross-sectional view perpendicular to the tube axis at the open end 28, FIG. 6B is a cross-sectional view along the line AA ′ in FIG. 6A, and FIG. 6A is a cross-sectional view taken along the line BB ′ in FIG. 6A, and FIG. 6D is a cross-sectional view taken along the line AA ′ in FIG. 6A when the left inner wall in FIG. FIG. In FIG. 6, the number of repetitions of increasing / decreasing the curvature along the inner circumferential direction is displayed differently from that in FIGS. 2 and 4, but this is for convenience of explanation.

  As shown in FIG. 6A, the cross section of the inner wall at the open end 28 of the bass reflex port 20 according to the present embodiment is convex when the inner wall protrudes away from the tube axis when the inner wall is viewed from the tube axis. And a portion in which the inner wall is recessed in the tube axis direction are repeated along the inner circumferential direction of the inner wall. That is, in the cross section of the open end 28, the center of curvature of the inner wall that protrudes outside the circle indicated by the broken line centered on the tube axis is located on the tube axis side when viewed from the inner wall, and the inner wall of the inner wall The curvature along the circumferential direction shows a positive value. In addition, the curvature center of the inner wall that is recessed and recessed inside the circle indicated by the broken line centered on the tube axis is located on the opposite side of the tube axis from the inner wall, and the curvature along the inner circumferential direction of the inner wall. Indicates a negative value. FIG. 6B shows the inner wall in the tube axis direction at the positions θ1 and θ7 in the inner circumferential direction of the opening end 28 shown in FIG. 6A. As shown in FIGS. 6A and 6B, the inner circumferential positions θ1 and θ7 are portions where the inner wall is convex when the inner wall is viewed from the tube axis, and the opening end 28 is wide and outside. It is a position that spreads out. For this reason, at the positions θ1 and θ7 in the inner circumferential direction, the degree of expansion of the gas flow path increases from the center side of the bass reflex port 20 toward the opening end 28 side. Therefore, at the positions θ1 and θ7 in the inner circumferential direction, as shown in FIG. 6B, the region where the gas flow near the inner wall is separated from the inner wall at the position L1 in the tube axis direction and becomes a turbulent flow (vortex). 52 occurs.

  In addition, at the positions θ3 and θ5 in the inner circumferential direction, as with the positions θ1 and θ7, the inner wall is a convex portion when viewed from the tube axis. A region 52 that becomes a turbulent flow occurs at the position L1 in the axial direction.

  On the other hand, FIG. 6C shows the inner wall in the tube axis direction at the positions θ0 and θ6 in the inner circumferential direction of the opening end 28 shown in FIG. As shown in FIGS. 6A and 6C, the inner circumferential positions θ0 and θ6 are portions where the inner wall is concave when the inner wall is viewed from the tube axis, and the opening end 28 is narrow and outward. It is a spreading position. For this reason, at the positions θ0 and θ6 in the inner circumferential direction, the degree of expansion of the gas flow path is reduced from the center side of the bass reflex port 20 toward the opening end 28 side. For this reason, at the positions θ0 and θ6 in the inner circumferential direction, as shown in FIG. 6C, the region where the gas flow near the inner wall is separated from the inner wall at the position L2 in the tube axis direction and becomes a turbulent flow (vortex). 52 occurs.

  Further, at the positions θ2 and θ4 in the inner circumferential direction, as in the positions θ0 and θ6, the inner wall is a concave portion when the inner wall is viewed from the tube axis, so that the tube axis similar to that in FIG. A region 52 that becomes a turbulent flow occurs at the position L2 in the direction.

  In FIG. 6D, positions θ1 to θ7 corresponding to the positions θ1 to θ7 in the inner circumferential direction of FIG. 6A are shown on the left side of the A-A ′ line. As shown in FIG. 6D, the turbulent (vortex) region 52 is located at a position L1 in the tube axis direction at positions θ1, θ3, θ5, and θ7 where the inner wall viewed from the tube axis is convex. Is generated at positions θ0, θ2, θ4, and θ6 where the inner wall viewed from the tube axis is concave, and is generated at a position L2 in the tube axis direction. At positions between these inner circumferential positions θ0 to θ7, the tube axis It occurs at a position between the directional positions L1 and L2. That is, the region 52 that becomes a turbulent flow (vortex) occurs at a position in the tube axis direction corresponding to the curvature along the inner circumferential direction (in other words, the position of the center of curvature or the sign of the curvature), and the tube axis direction is the amplitude. It is distributed in a wave shape with the inner circumferential direction as the traveling direction. For this reason, when viewed in the entire area in the inner circumferential direction, the region 52 that becomes a turbulent flow (vortex) is distributed over a wide range in the tube axis direction in the vicinity of the opening end 28 of the bass reflex port 20 according to the present embodiment.

  Next, the difference from the conventional bass reflex port in which the cross section perpendicular to the tube axis in the vicinity of the open end is rectangular and elliptical will be described. A conventional bass reflex port having a rectangular cross section has a constant curvature along each inner side of the inner wall, and is similar to the conventional bass reflex port having a circular cross section. In addition, the conventional bass reflex port having an elliptical cross section changes the curvature along the inner circumferential direction of the inner wall, but the degree of change in the curvature is small, and the position of the center of curvature of the inner wall is a tube viewed from the inner wall. There is no position opposite to the shaft, and the inner wall viewed from the tube shaft does not become concave. For this reason, in the case of an ellipse, the curvature along the inner circumferential direction continues to have a value close to the inner circumferential direction, so that the position in the tube axis direction in which a region that becomes a turbulent flow (vortex) occurs does not change significantly. Thereby, in the case of an ellipse, it is thought that the area | region which becomes a turbulent flow (vortex) in each position of an inner peripheral direction tends to generate | occur | produce locally in the same position of a pipe-axis direction. On the other hand, in the bass reflex port 20 according to the present embodiment, the curvature along the inner peripheral direction of the inner wall near the opening end 28 is repeatedly increased and decreased, and the inner wall extends from the tube axis in a cross section perpendicular to the tube axis near the opening end 28. When viewed, the part where the inner wall protrudes in the direction away from the tube axis and is convex, and the part where the inner wall falls into the tube axis direction and is concave are repeated along the inner circumferential direction of the inner wall. Therefore, the curvature along the inner circumferential direction changes greatly. For this reason, the position in the tube axis direction in which a region of turbulent flow (vortex) is generated changes greatly. Thereby, in the bass reflex port 20 according to the present embodiment, the region 52 that becomes a turbulent flow (vortex) is distributed over a wide range in the tube axis direction.

  As described above, in the acoustic device 1 according to the present embodiment, the shape of the inner wall in the vicinity of the opening end 28 of the bass reflex port 20 has a cross-sectional area perpendicular to the tube axis of the space surrounded by the inner wall of the bass reflex port 20. When the inner wall is viewed from the tube axis in a cross section perpendicular to the tube axis in the vicinity of the opening end 28, the inner wall gradually expands and gradually increases and decreases along the inner circumferential direction. Is formed into a corolla shape in which a portion protruding in a direction away from the tube axis and having a convex shape and a portion in which the inner wall is recessed in the tube axis direction are repeated along the inner circumferential direction of the inner wall This prevents a region that becomes a turbulent flow (vortex) in the gas flow path via the bass reflex port 20 from being locally generated. For this reason, generation | occurrence | production of the abnormal noise resulting from the suction and discharge of the gas in the bass reflex port 20 can be reduced.

<Other embodiments>
Although one embodiment of the present invention has been described above, other embodiments are conceivable for the present invention. For example:

(1) In the bass reflex port 20 of the acoustic device 1 according to the above-described embodiment, the corolla shape is shown as an example in which the shape of the inner wall is changed along the inner circumferential direction. The point is that the curvature along the inner circumferential direction of the inner wall may be repeatedly increased or decreased in the vicinity of the opening end 28 of the bass reflex port 20. In addition, the repetition interval of the increase / decrease of curvature along the inner circumferential direction of the inner wall (the repetition interval of the unevenness of the inner wall as viewed from the tube axis) may not be constant along the inner circumferential direction, and the number of repetitions of the increase / decrease of the curvature ( The number of repetitions of the unevenness of the inner wall viewed from the tube axis may be one or more.

(2) The shape in the vicinity of the opening end 28 of the bass reflex port 20 may be a flower crown shape, and the cross section in the vicinity of the opening end 28 may be a shape that is not point-symmetric or axially symmetric. By making the cross section in the vicinity of the opening end 28 into a shape that is not point-symmetric or axially symmetric, the region 52 that becomes a turbulent flow (vortex) can be reliably distributed over a wide range in the tube axis direction.

(3) In the bass reflex port 20 of the acoustic device 1 according to the above embodiment, the shape in the vicinity of the opening end 28 is a corolla shape. However, the shape near the opening end 29 may be a corolla shape, and both the shape near the opening end 28 and the vicinity of the opening end 29 may be a corolla shape. For example, by making the shape of both the vicinity of the opening end 28 and the vicinity of the opening end 29 into a corolla shape, a region where turbulent flow (vortex) is more reliably distributed can be distributed over a wide range, and the generation of abnormal noise can be further increased. It can be surely suppressed.

(4) In the above embodiment, the tube axis of the bass reflex port 20 is a straight line, but is not limited thereto. For example, the tube axis may be bent near the center of the bass reflex port 20.

(5) In the above-described embodiment, the open end 28 of the bass reflex port 20 is in contact with a surface orthogonal to the tube axis. However, for example, the opening end 28 located inside the enclosure 10 may be in contact with a surface inclined with respect to a surface orthogonal to the tube axis.

(6) The straight portion 22 of the bass reflex port 20 of the acoustic device 1 according to the above embodiment has a circular cross section in a plane perpendicular to the tube axis. However, the straight portion 22 of the bass reflex port 20 is not limited to a structure having a circular cross section. For example, the cross-sectional shape of the straight portion 22 of the bass reflex port 20 may be rectangular.

(7) In the above embodiment, the bass reflex port 20 is divided into the straight portion 22 and the flare portions 24 and 25. However, the cross-sectional area continuously increases from the center toward both ends without providing the straight portion 22. You may make it become.

(8) A feature of the technical idea of the present invention resides in a means for reducing abnormal noise generated from a tube serving as a gas flow path, such as the bass reflex port 20, and an open end of the tube serving as a gas flow path. In the vicinity, the area of the cross section perpendicular to the tube axis of the space surrounded by the inner wall of the tubular body gradually increases as it approaches the open end of the tubular body, and the curvature of the inner wall is repeatedly increased and decreased along the inner circumferential direction. It is in the point. Therefore, the present invention can be applied to mufflers such as two-wheeled vehicles and four-wheeled vehicles, air-conditioning intake / exhaust ducts, musical instruments, and the like.

  DESCRIPTION OF SYMBOLS 1 ... Sound apparatus, 10 ... Enclosure, 11 ... Front, 18, 21 ... Opening part, 20, 20A, 20B ... Bass reflex port, 22 ... Straight part, 24, 25 ... Flare part, 28, 28B, 29 ... Opening end, 52, 52B ... A turbulent region, SP ... Speaker unit.

Claims (3)

  A tubular body forming a gas flow path, the area of the cross section perpendicular to the tube axis of the space surrounded by the inner wall of the tubular body gradually increases as it approaches the opening end of the tubular body, A tubular body characterized in that the inner wall is smoothly waved in the circumferential direction.   The bass reflex port is open at both ends and forms a gas flow path inside and outside the speaker enclosure, and the area of the cross section perpendicular to the tube axis of the space surrounded by the inner wall of the bass reflex port is the open end of the bass reflex port. A bass reflex port characterized in that it gradually widens as it approaches and the inner wall in the vicinity of the opening end undulates smoothly in the circumferential direction. A housing having an opening;
A tubular body that is disposed inside the housing, has both ends open, and one open end is fixed to the opening of the housing to form a gas flow path inside and outside the housing, the tubular body An area of the cross section perpendicular to the tube axis of the space surrounded by the inner wall of the tube gradually expands as it approaches the opening end of the tube body, and the tube body in which the inner wall near the opening end smoothly undulates in the circumferential direction
An acoustic device comprising:

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