Background noise generator

Abstract

To provide a background noise generation device that has simple constitution and is reducible in manufacturing cost, and provides an indoor environment in which outdoor life noise is hardly heard.SOLUTION: A background noise generation device comprises an air flow passage (duct 16C) which is provided in a building so as to link the outside of the building to the inside of a room, and a resistance device which is provided in the air flow passage on a side close to a room, and serves resistance when air passes into the air flow passage. An upwind-side resistance device 2 and a downwind-side resistance device 3 which constitute the resistance device 1X have resistance plates, having through holes (an upwind hole 21 and a downwind hole 31) formed to circulate air to a plate having an outer diameter corresponding to the inner diameter of the air flow passage, respectively, those resistance plates being installed inside the air flow passage. The number of through holes of the upwind-side resistance device and the number of through holes of the downwind-side resistance device are equal to each other, and the through holes of the upwind-side resistance device and the through holes of the downwind-side resistance device face each other, one to one.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a background noise generating device that generates background noise indoors to counteract everyday life sounds from outside the room. [Background technology]

[0002] In recent apartment buildings and other shared housing, the level of sound entering the building from the outside has been reduced due to high insulation and airtightness, and in residential areas, the A-weighted sound pressure level inside the building at night can reach the low 20 dB range. In this way, in an environment where the level of sound entering the building from outside is low, the problem arises that the sounds of daily life from outside can be heard and become bothersome inside the building. Note that "sounds of daily life from outside" refers to sounds of daily life from upper floors or neighboring residences in an apartment building, sounds of daily life from neighboring houses in a detached building, etc. A method is known in which a resistance device is installed inside an air intake hole formed in the exterior wall of a building, and background noise (total noise other than the target noise that occurs in the surrounding environment of the target noise) is generated to increase the volume of sound that flows into the room through the air intake hole, thereby creating an indoor environment in which it is difficult to hear everyday sounds from outside (see Patent Document 1, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-136091 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the resistance device used in the above-mentioned method, the two resistance plates that make up the resistance device have completely different shapes, which makes the configuration of the resistance device complex and poses issues in terms of manufacturing costs, etc. The present invention provides a background noise generating device which has a simple configuration, can be manufactured at low cost, and can realize an indoor environment in which it is difficult to hear everyday sounds from outside the room. [Means for solving the problem]

[0005] The background noise generating device according to the present invention comprises a duct provided in the ceiling space, underfloor space or within-wall space of a building to communicate between an air supply means provided on the exterior wall of a building for taking in outside air from the outside of the building into the building and a room within the building, and a resistance device provided on the inside of the duct on the side closer to the room and providing resistance when air passes inside the duct, the resistance device comprising a leeward resistance device installed in the duct at a position closer to the room, and an upwind resistance device installed in the duct at a position farther from the room than the downwind resistance device, the upwind side resistance device and the downwind side resistance device each having a resistance plate with an outer diameter corresponding to the inner diameter of the duct and with through holes formed therein to allow air to flow, and in the background noise generating device in which these resistance plates are installed inside the duct, the number of through holes in the upwind side resistance device and the number of through holes in the downwind side resistance device are the same, and of The through holes are configured to face each other in a one-to-one relationship. In addition, the size of the diameter of the through hole of the upwind resistance device and the size of the diameter of the through hole of the downwind resistance device facing each other are different. The windward-side resistance device is also characterized in that the diameter of the through hole of the windward-side resistance device is larger than the diameter of the through hole of the leeward-side resistance device. The background noise generating device according to the present invention has a simple configuration, can reduce manufacturing costs, and can realize an indoor environment in which it is difficult to hear everyday sounds from outside the room. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a building that employs a background noise generating device. [Diagram 2] FIG. 1 is a floor plan showing an example of a building that employs a background noise generating device. [Diagram 3]FIG. [Figure 4] 1A and 1B are diagrams showing a windward resistance device and a leeward resistance device, in which (a) is a front view, and (b) and (c) are perspective views. [Diagram 5] Figure showing the results of Experiment 1. [Figure 6] Figure showing the results of Experiment 2. [Figure 7] Figure showing the results of Experiment 3. [Figure 8] Figure showing the results of Experiment 4. [Figure 9] Figure showing the results of Experiment 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] EMBODIMENT 1 As shown in FIG. 1, the background noise generating device of embodiment 1 is installed in a building configured to supply air taken into building 10 from outside the building 10 to rooms 12 within building 10 via attic space 11S, for example, in a building 10 that employs a Type 1 ventilation method as a 24-hour ventilation system in which outside air is forcibly supplied to the interior of building 10 from outside the building 10 and air is forcibly exhausted from the interior of building 10 to the outside of building 10. The background noise generating device is configured to include a duct 16C that is installed in building 10 to connect the outside of building 10 with the inside of the building, serving as an air flow passage that guides air from the outside of building 10 to room 12 within building 10, and a resistance device 1X that is installed inside the end side of duct 16C that is closer to room 12 and provides resistance when air passes inside duct 16C. In other words, this background noise generating device is a device that increases the volume of the sound when air flows into room 12 through duct 16C, resistance device 1X in duct 16C, and air intake 1 provided in ceiling panel 11 of room 12 by providing resistance device 1X on the inside of the end side of duct 16C closer to room 12 to provide resistance to the air passing through, thereby realizing an indoor environment in which it is difficult to hear everyday sounds from outside, even in room 12 that faces exterior wall 9 of building 10 and has no air intake 1. In addition, when there is no resistance device 1X inside duct 16C that provides resistance to the air passing through, the sound generated when air flows into room 12 through duct 16C and air intake 1 is also background noise. Strictly speaking, in the present invention, the sound generated when air passes through resistance device 1X (meaningless sound) is added to the background noise. However, in this specification, the sound that is generated when air passes through resistance device 1X installed inside duct 16C and that can be heard in room 12 is defined and explained as background noise.

[0008] As shown in Figures 1 and 2, in a building 10 such as an apartment building (condominium) that employs the first type of ventilation method of a 24-hour ventilation system, air is forcibly taken in from the outside of the building 10 into the building 10, distributed to each room 12, 12... inside the building 10, and the air is forcibly exhausted from a specific location to the outside of the building 10. Therefore, in the background noise generating device of embodiment 1, air intakes 1, 1... are provided in the ceiling panels 11, 11... of each of the multiple rooms 12, 12... in order to distribute air taken in from outside the building 10 to the inside of the building 10 to each of the multiple rooms 12, 12... within the building 10, and resistance devices 1X, 1X... are provided inside the ducts 16C, 16C... connected to each of the air intakes 1, 1..., at a position close to the air intakes 1, 1....

[0009] For example, as shown in Figures 1 and 2, building 10 is equipped with an air supply means 13 that takes in outside air from outside building 10 into the inside of building 10, a heat exchange system 14, an inside air intake hole 17 provided in a ceiling panel 11 of a specific room (e.g. a bedroom), each air supply hole 1, 1... provided in each ceiling panel 11, 11... of each room 12, 12..., and an exhaust means 15 that exhausts air inside building 10 to the outside of building 10. An outside air outlet (an opening at the other end of a cylinder, described later) 13a of the air supply means 13 and an outside air intake 14a of the heat exchange system 14 are connected by a duct 16A. 2, the inside air intake 14b of the heat exchange system 14 and the under-ceiling opening of the inside air intake hole 17 provided in the ceiling board 11 of the specific room 12 (e.g., a bedroom) are connected by a duct 16B. Note that it is sufficient that there is one or more specific rooms, and that there is also sufficient that there is one or more inside air intake hole 17. Furthermore, the treated air discharge outlet 14c of the heat exchange system 14 is connected to each of the under-ceiling openings of each air supply hole 1, 1... provided in each ceiling panel 11, 11... of each room 12, 12... (the other end opening (upper end opening) 1b of the one-end opening side cylindrical portion 1B of the cylindrical part 1A described later) by ducts 16C, 16C... As these ducts 16A, 16B, and 16C, for example, circular pipe ducts having flow paths with circular cross sections are used. In addition, in the floor plan (floor plan) of building 10 in Figure 2, E is the entrance, Cd is the hallway, BR is the bedroom, UB is the bathroom with toilet, W is the washroom, K is the kitchen, WR is the Western-style room, C is the closet, JR is the Japanese-style room, and LD is the living-dining room.

[0010] The air supply means 13 is a means for taking in outside air into the attic space 11S, and includes, for example (not shown) a through hole formed in the exterior wall 9 of the building 10, a cylinder that is installed within the through hole to form an outside air intake hole (air supply hole), and a forced air supply means such as an air supply fan provided on the other end opening side of the cylinder that is closer to the heat exchange system 14.

[0011] As shown in FIG. 2, the heat exchange system 14 is a device that performs heat exchange processing between outside air taken in from outside the building 10 by the air supply means 13 and inside air taken in from a specific room (e.g., a bedroom), and then distributes and supplies the air after this heat exchange processing (treated air) to each room (each room) 12, 12.... The heat exchange system 14 may have an air cleaning function in addition to the heat exchange function.

[0012] As shown in FIG. 3, the air supply hole 1 is formed by a cylindrical part 1A having one end opening 1a communicating with a room 12 via a through hole 11a formed in a ceiling board 11 that forms the ceiling, and the other end opening 1b communicating with a duct 16C for taking in air from outside the building 10. A resistance device 1X is provided at a position close to the air inlet 1 inside a duct 16C connected to the air inlet 1 formed by the cylindrical part 1A.

[0013] As shown in Figure 3, the cylindrical part 1A forming the air supply hole 1 is composed of one end opening side cylindrical portion 1B formed by a cylindrical portion, the other end opening side cylindrical portion 1C formed by a cylindrical portion having a diameter smaller than the diameter of the one end opening side cylindrical portion 1B, and a circular ring-shaped blocking plate 1D that blocks the space between the other end opening edge of the one end opening side cylindrical portion 1B and the one end opening edge of the other end opening side cylindrical portion 1C. That is, the cylindrical part 1A is a stepped cylindrical part in which two cylindrical parts of different diameters are combined, the cylindrical part 1B having one open end and the cylindrical part 1C having a smaller diameter than the cylindrical part 1B having one open end. In other words, the cylindrical part 1A is a stepped cylindrical part whose cross-sectional shape along the central axis is convex.

[0014] Specifically, the air supply hole 1 is formed by an inner through hole 1H of a cylindrical part 1A attached so as to pass through the through hole 11a. The inner through hole 1H is formed by a stepped inner through hole partitioned by an inner through hole 1HB, which is the inner surface of the cylindrical portion 1B on the one end opening side, an inner through hole 1HC, which is the inner surface of the cylindrical portion 1C on the other end opening side, and the inner surface of the blocking plate 1D.

[0015] An attachment flange 1F is provided on the edge of one end opening (lower end opening) 1a of one end opening side cylindrical portion 1B of cylindrical part 1A. The cylindrical part 1A is inserted through through hole 11a from the other end opening (upper end opening) 1b side of other end opening side cylindrical portion 1C, and the upper surface of attachment flange 1F is brought close to the lower surface of ceiling board 11. Then, for example, a screw or bolt is inserted through attachment flange 1F and ceiling board 11 and fastened to a ceiling substrate (not shown), thereby attaching cylindrical part 1A to ceiling board 11, and air supply hole 1 that communicates room 12 with ceiling space 11S is formed in ceiling board 11. In addition, it is preferable that a lid 1E equipped with an opening / closing body 1R such as a louver opening / closing part for opening and closing the one end opening 1a of the cylindrical part 1A (the room side opening of the air intake hole 1) 1a be removably attached to the one end opening 1a side of the cylindrical part 1A.

[0016] The exhaust means 15 is a means configured to exhaust air inside the building to the outside, for example, by including a through hole formed in the ceiling or the like of a specific room 12 (for example, a bathroom or washroom) (not shown), a cylinder that is fitted into the through hole to form an internal air exhaust hole, and a forced exhaust means such as an exhaust fan provided on the opening side of the cylinder located in the ceiling space or the like.

[0017] In addition, an air supply fan is provided near the outside air intake 14a and the inside air intake 14b of the heat exchange system 14, and an exhaust fan is provided near the treated air delivery outlet 14c of the heat exchange system 14.

[0018] Therefore, the outside air taken in from the outside of the building 10 to the inside of the building 10 by the air supply means 13 is taken in through the duct 16A and the outside air inlet 14a arranged in the ceiling space 11S to the heat exchange system 14. Also, the inside air of a specific room 12 (for example, a bedroom) is taken in through the inside air inlet 17 provided in the ceiling board 11, the duct 16B and the inside air inlet 14b arranged in the ceiling space 11S to the heat exchange system 14. Then, the heat exchange system 14 performs a heat exchange process between the outside air and the inside air, and the air after this heat exchange process is distributed and supplied to each room 12, 12... via the treated air outlet 14c, the ducts 16C, 16C..., the resistance devices 1X, 1X... provided in each duct 16C, 16C..., and each air supply hole 1, 1... provided in each ceiling board 11, 11... of each room 12, 12....

[0019] In addition, in the first type ventilation method of the 24-hour ventilation system, the amount of air taken in from outside the building 10 to inside the building 10 by the air supply means 13 is adjusted to be equal to the amount of air exhausted from inside the building 10 to the outside of the building 10 by the exhaust means 15.

[0020] As shown in Figure 3, the background noise generating device of embodiment 1 is configured to include a resistance device 1X that provides resistance to the air passing through on the inside of the end side of a duct 16C closer to room 12, which is connected to a cylindrical part 1A that is provided on the ceiling of room 12 and forms an air intake 1 for supplying air from the attic space 11S side to room 12, in other words, inside duct 16C near the connection between duct 16C and cylindrical part 1A. For example, when performing work to insert a resistance device 1X from the end opening of a duct 16C connected to a cylindrical part 1A on the side closer to the room 12 and install the resistance device 1X inside the duct 16C, the resistance device 1X is provided within reach of the worker from the end opening of the duct 16C on the side closer to the room 12.

[0021] As shown in Figure 3, the resistance device 1X is composed of an upwind side resistance device 2 provided on the inside of the end side of the duct 16C closer to the room 12, and a downwind side resistance device 3 installed on the inside of the end side of the duct 16C closer to the room 12 at a position closer to the room 12 than the upwind side resistance device 2. In other words, the resistance device 1X is composed of a downwind side resistance device 3 installed on the inside of the end side of the duct 16C closer to the room 12, and an upwind side resistance device 2 installed farther from the room 12 than the downwind side resistance device 3.

[0022] As shown in Figure 4, the upwind resistance device 2 is composed of a perforated circular plate 22 which functions as a resistance plate with an upwind hole 21 formed in the center of a circular plate having an outer diameter dimension corresponding to the inner diameter (flow path diameter) dimension of the duct 16C, and a cylindrical body 23 formed to extend from the outer peripheral edge of the perforated circular plate 22. The cylindrical body 23 is fixedly installed inside the duct 16C so that the outer peripheral surface of the cylindrical body 23 is in contact with or close to the inner peripheral surface 16U of the duct 16C, thereby forming an upwind hole 21 inside the duct 16C, which is composed of a central circular through hole centered on the central axis of the duct 16C. The cylinder 23 is a cylinder with both ends open and formed with an outer diameter dimension corresponding to the inner diameter dimension of the duct 16C constituted by a circular duct having a flow path (air flow passage) with a circular cross section, for example. The holed circular plate 22 is a resistance plate having an outer diameter corresponding to the diameter of one open end of the cylinder 23 and having an upwind hole 21 formed in the center thereof. That is, the windward-side resistance device 2 comprises a circular plate 22 with holes and a cylindrical body 23 , and is configured by joining one end opening side of the cylindrical body 23 and the outer periphery side of the circular plate 22 with holes. In other words, the upwind side resistance device 2 comprises a circular plate 22 with holes which serves as a resistance plate when air (wind) flows through the duct 16C (air flow passage), upwind holes 21 which serve as flow holes when air flows through the duct 16C, and a cylindrical body 23 having an outer peripheral surface which serves as the installation surface when the upwind side resistance device 2 is installed on the inner peripheral surface within the duct 16C.

[0023] The windward hole 21 is formed by a central circular through hole having the center 2C of the circular plate that is the base of the circular plate with holes 22 as the center of the hole. The windward hole 21 may be a circular through hole having a diameter smaller than the diameter of the circular plate that is the base of the holed circular plate 22 . The cylinder 23 is a cylinder having a central axis 23C that passes through the center 2C of the original circular plate from which the holed circular plate 22 is formed and is perpendicular to the plate surface (flat surface) of the holed circular plate 22.

[0024] Furthermore, the windward resistance device 2 is configured, for example, so that the outer peripheral surface of the perforated circular plate 22 and the inner peripheral surface of one end side of the cylindrical body 23 are connected and integrated together, so that one end face of the cylindrical body 23 and the plate surface of the perforated circular plate 22 are positioned on the same plane, or so that one end face of the cylindrical body 23 and the outer peripheral edge side plate surface of the perforated circular plate 22 (the outer peripheral edge side plate surface on the cylindrical body 23 side) are connected and integrated together. The windward resistance device 2 may be formed by integrally forming a circular plate 22 with a cylindrical body 23, or may be formed by joining a circular plate 22 with a hole and a cylindrical body 23 which are formed separately to form an integral body.

[0025] The windward-side resistance device 2 is installed such that the outer circumferential surface of the cylindrical body 23 directly contacts the inner circumferential surface 16U of the duct 16C in close contact therewith. Alternatively, the windward resistance device 2 is fixed to the inner surface 16U of duct 16C using a fixing means such as an adhesive, adhesive tape or welding, with an adhesion-promoting sheet material provided on the outer surface of the cylinder 23 to fill the gap between the outer surface and the inner surface 16U of duct 16C and enhance adhesion between the outer surface of the cylinder 23 and the inner surface 16U of duct 16C, and the outer surface of the cylinder 23 is positioned so that it is close to the inner surface 16U of duct 16C via the adhesion-promoting sheet material. The adhesion promoting sheet material may be a sheet material made of a urethane or rubber material. In this way, by installing the upwind resistance device 2 in a fixed state inside the duct 16C, the plate portion of the perforated circular plate 22 functions as a resistance plate, and the upwind hole 21 is configured to function as a flow path diameter reduction means for reducing the flow path diameter of the duct 16C. In other words, the upwind resistance device 2 is fixedly installed inside the duct 16C so that the outer peripheral surface of the cylinder 23 is in contact with or close to the inner peripheral surface 16U of the duct 16C, thereby providing a perforated circular plate 22 functioning as a resistance plate and an upwind hole 21 functioning as a flow path diameter reduction means within the duct 16C.

[0026] The windward side resistance device 2 and the leeward side resistance device 3 have the same configuration except that the diameter of the windward hole 21 and the diameter of the leeward hole 31 are different, or they have the same configuration in all respects. In other words, when the upwind side resistance device 2 and the downwind side resistance device 3 are different, the only difference is whether the radial dimension of the upwind hole 21 is formed to be larger than the radial dimension of the downwind hole 31 (see Figure 4), or conversely, whether the radial dimension of the upwind hole 21 is formed to be smaller than the radial dimension of the downwind hole 31.

[0027] That is, the downwind resistance device 3 is a resistance device comprising a circular plate with holes 32 equivalent to the circular plate with holes 22 and a cylindrical body 33 identical to the cylindrical body 23, and the circular plate with holes 32 is configured to function as a resistance plate having downwind holes 31 equivalent to the upwind holes 21. In other words, the contents of the downwind side resistance device 3 are the same as those of the upwind side resistance device 2 described above, except that the upwind hole 21 is replaced with the downwind hole 31, the perforated circular plate 22 with the hole 32, the cylinder 23 with the cylinder 33, the center 2C of the circular plate with the center 3C, and the central axis 23C of the cylinder 23 with the central axis 33C of the cylinder 33.

[0028] That is, the upwind side resistance device 2 and the downwind side resistance device 3 each have a perforated circular plate 22, 32 as a resistance plate with upwind holes 21 and downwind holes 31 (through holes) formed therein for allowing air to flow through a circular plate having an outer diameter dimension corresponding to the inner diameter dimension of the duct 16C which forms an air flow passage, and these perforated circular plates 22, 32 are installed inside the duct 16C to form the resistance device 1X. The resistance device 1X is configured such that the number of upwind holes 21 (through holes) of the upwind side resistance device 2 is the same as the number of downwind holes 31 (through holes) of the downwind side resistance device 3, and the upwind holes 21 of the upwind side resistance device 2 and the downwind holes 31 of the downwind side resistance device 3 face each other in a one-to-one relationship.

[0029] In the first embodiment, when the diameters of the upwind hole 21 and the downwind hole 31 which face each other are different, the upwind hole 21 and the downwind hole 31 are formed as similar circular through holes. In addition, the center 2C of the upwind hole 21 is positioned on the central axis 23C of the cylinder 23, and the center 3C of the downwind hole 31 is positioned on the central axis 33C of the cylinder 33, so that the upwind hole 21 and center 2C and the center 3C of the downwind hole 31, which face each other one-to-one within the duct 16C, are positioned on the central axis of the duct 16C.

[0030] Furthermore, as shown in Figures 3 and 4, if a resistance device 1X is configured in such a manner that the other end face of the cylinder 23 of the upwind side resistance device 2 is butted against the other end face of the cylinder 33 of the upwind side resistance device 3, then by adjusting the tube length of the cylinder 23 and the tube length of the cylinder 33, a resistance device 1X can be formed in which a distance H is set between the upwind hole 21 and the downwind hole 31. Furthermore, by installing the other end face of the cylinder 23 of the upwind side resistance device 2 and the other end face of the cylinder 33 of the upwind side resistance device 3 inside the duct 16C so that they are spaced apart, the distance H between the upwind hole 21 and the downwind hole 31 can be freely set.

[0031] As a result of the above, a background noise generating device is configured, which is provided with a resistance device 1X formed by the windward side resistance device 2 and the leeward side resistance device 3, on the inside of the end side of the duct 16C closer to the room 12. That is, a background noise generating device is installed on the ceiling side of the room 12. For example, as shown in Figure 3, the windward resistance device 2 is installed in the duct 16C so that the cylinder 23 is located closer to the room 12 and the circular plate with holes 22 is located on the windward side (the side farther from the room 12), and the downwind resistance device 3 is installed in the duct 16C so that the cylinder 33 is located closer to the room 12 and the circular plate with slits 32 is located on the windward side (the side farther from the room 12).

[0032] According to the background noise generating device of embodiment 1, the resistance device 1X installed inside the duct 16C is composed of an upwind side resistance device 2 and a downwind side resistance device 3 of similar configuration, so that it is possible to provide a background noise generating device that has a simple configuration, can reduce manufacturing costs, and can realize an indoor environment in which it is difficult to hear daily living sounds from outside the room. In addition, since a resistance device 1X is provided on the inside of the end side of duct 16C closer to room 12, the volume of the sound generated when air flows into room 12 through resistance device 1X provided in duct 16C and cylindrical part 1A forming air intake 1 becomes larger, so that an indoor environment in which it is difficult to hear everyday sounds from outside can be realized even in room 12 which does not have an air intake 1 facing exterior wall 9.

[0033] Furthermore, according to the background noise generating device of embodiment 1, when air is distributed and supplied from the heat exchange system 14 to each of the rooms 12, 12... via the ducts 16C, 16C... and the air intakes 1, 1... provided in the ceiling panels 11, 11... of each of the rooms 12, 12..., sound is generated due to resistance, etc. as the air passes through the resistance device 1X provided in each of the ducts 16C, 16C... Therefore, in each of the plurality of rooms 12, 12... that do not have an air supply hole 1 facing the outer wall 9 of the building 10, an indoor environment in which living sounds from outside are difficult to hear can be realized. In addition, by adopting the first type ventilation system as the ventilation system for the building, ventilation can be smooth, and an indoor environment can be achieved in room 12 in which it is difficult to hear everyday sounds from outside.

[0034] In order to confirm the effect of the background noise generating device according to the first embodiment, the following Experiments 1 to 5 were carried out based on the following experimental device and method. Experimental equipment and methods A ceiling model simulating a ceiling was placed in an anechoic chamber, a through hole was formed in the ceiling model, and a test specimen of the resistance device 1X was placed inside one end of a duct. One end of the duct was then connected to the through hole from the underside of the ceiling model. Furthermore, a blower fan was installed on the other opening end of the duct, and an experimental device was created in which the blower fan was driven to blow air into the duct. Then, after placing a microphone below the through hole in an anechoic chamber, the blower fan was driven to measure the 1 / 3 octave band sound pressure level and A-weighted sound pressure level of the sound generated when the wind passed through the test specimen of the resistance device 1X, thereby verifying the difference in effect due to the difference in the test specimen of the resistance device 1X. In the experiment, a circular duct of approximately 20 m was used, and a sound-absorbing box was installed midway through the duct. To prevent the sound generated by the blower fan from being measured, air was blown from the blower fan to the test specimen of the resistance device 1X inside the duct. When measuring the 1 / 3 octave band sound pressure level and the A-weighted sound pressure level, the microphone was placed in the anechoic chamber so that the center position of the microphone's head case coincided with a position 1 m directly below the center position of the through hole formed in the ceiling model. Since the operating noise is a steady sound, the equivalent sound pressure level was calculated for 20 seconds. The fan air volume was measured using an air volume meter.

[0035] The specifications common to the duct, the upwind resistance device 2, and the downwind resistance device 3 used in Experiments 1 to 5 are as follows: (1) Duct Duct inner diameter: 154mm. Duct outer diameter: 165mm. (2) Windward resistance device 2 and leeward resistance device 3 -Outer diameter of cylinder 23,33 is 156mm. -Inner diameter of cylinder 23,33 is 154.4mm. The thickness of the perforated circular plates 22, 23 is 0.8 mm.

[0036] Test 1 The diameter of the windward hole 21 of the windward-side resistance device 2 constituting the resistance device 1X described in the first embodiment was set to 42.5 mm, and the diameter of the leeward hole 31 of the leeward-side resistance device 3 was set to 37.5 mm. The distance H (see FIG. 3) between the windward hole 21 and the leeward hole 31 (i.e., the distance between the holed circular plate 22 and the holed circular plate 32) was varied. Using test specimens 1 to 5, the air volume blown from the blower fan (hereinafter referred to as fan air volume) was set to 50.0 m 3 An experiment was conducted to verify how the 1 / 3 octave band sound pressure level and the A-weighted sound pressure level would change depending on the differences in each test specimen 1 to 5 when the test volume was set to 1 / h. In other words, this experiment was conducted to verify how the 1 / 3 octave band sound pressure level and A-weighted sound pressure level would change by changing the spacing H under the condition that the diameter of the upwind hole was 42.5 mm and the diameter of the downwind hole was 37.5 mm (the diameter of the upwind hole was larger than the diameter of the downwind hole). The results of the experiment 1 are shown in Fig. 5. The results of the experiment in the absence of the resistance device 1X described in the first embodiment are shown for the test piece 6 in Fig. 5.

[0037] Experiment 2 The diameter dimension of the upwind hole 21 of the upwind side resistance device 2 constituting the resistance device 1X described in embodiment 1 was fixed at 42.5 mm, the diameter dimension of the downwind hole 31 of the downwind side resistance device 3 was fixed at 37.5 mm, and the spacing H was fixed at 5 mm. Using test specimens 1 to 7 with different fan air volumes, an experiment was conducted to verify how the 1 / 3 octave band sound pressure level and A-weighted sound pressure level would change depending on the differences between test specimens 1 to 7. That is, this was an experiment to verify how the 1 / 3 octave band sound pressure level and the A-weighted sound pressure level would change when the interval H was made shorter than in Experiment 1 and the air volume was changed. The results of Experiment 2 are shown in FIG.

[0038] Test 3 The resistance device 1X described in the first embodiment has a windward hole 21 of the windward resistance device 2 with a diameter of 42.5 mm, a leeward hole 31 of the leeward resistance device 3 with a diameter of 47.5 mm, and a fan air volume of 50.0 m 3 An experiment was conducted using test specimens 1 to 5 with a fixed pitch of 1 / 2 mm / h and different spacing H to verify how the 1 / 3 octave band sound pressure level and A-weighted sound pressure level would change depending on the differences between test specimens 1 to 5. In other words, this experiment was conducted to verify how the 1 / 3 octave band sound pressure level and A-weighted sound pressure level would change by changing the spacing H under the condition that the diameter of the upwind hole was 42.5 mm and the diameter of the downwind hole was 47.5 mm (the diameter of the upwind hole was smaller than the diameter of the downwind hole). The results of Experiment 3 are shown in Fig. 7. An experiment was also conducted on a test specimen 6 provided with only the windward hole 21 with a diameter of 42.5 mm.

[0039] Test 4 The diameter of the windward hole 21 of the windward resistance device 2 constituting the resistance device 1X described in the first embodiment is set to 42.5 mm, and the fan air volume is set to 40.0 m 3 Test specimens 1 to 7 were used in which the length of the leeward hole 31 was fixed at 1 / h, the spacing H was fixed at 30 mm, and the diameter of the leeward hole 31 of the leeward resistance device 3 was varied, to verify how the 1 / 3 octave band sound pressure level and the A-weighted sound pressure level would change depending on the differences between test specimens 1 to 5. That is, this is an experiment to verify how the 1 / 3 octave band sound pressure level and the A-weighted sound pressure level change when the difference between the diameter of the upwind hole 21 and the diameter of the downwind hole 31 is changed. The results of Experiment 1 are shown in FIG.

[0040] Test 5 The diameter of the windward hole 21 of the windward-side resistance device 2 constituting the resistance device 1X described in the first embodiment is set to 42.5 mm, and the fan air volume is set to 50.0 m 3Test specimens 1 to 7 were used in which the length of the leeward hole 31 was fixed at 1 / h, the spacing H was fixed at 30 mm, and the diameter of the leeward hole 31 of the leeward resistance device 3 was varied, to verify how the 1 / 3 octave band sound pressure level and the A-weighted sound pressure level would change depending on the differences between test specimens 1 to 5. That is, the fan air volume in experiment 4 was 40.0 m 3 / h, fan air volume of 50.0 m 3 This experiment was conducted to verify what would happen to the 1 / 3 octave band sound pressure level and A-weighted sound pressure level when the setting was changed to / h. The results of Experiment 1 are shown in FIG.

[0041] 5 to 9 showing the experimental results, "windward" refers to the windward hole 21, "downwind" refers to the downwind hole 31, and "spacing" refers to the spacing H.

[0042] - Regarding the experimental results verified under the condition that the diameter dimension of the upwind hole 21 was 42.5 mm and the diameter dimension of the downwind hole 31 was 37.5 mm, i.e., the upwind hole diameter was 5 mm larger than the downwind hole diameter (hereinafter referred to as condition 1). (1) As is clear from FIG. 5, under condition 1, when the distance H was set to 10 mm to 50 mm (test specimens 1 to 5), the A-weighted sound pressure level was higher than when no resistance device was provided (test specimen 6). In particular, when the spacing H was set to 10 mm, 20 mm, and 30 mm (specimens 1 to 3 in Figure 5), the A-weighted sound pressure level was 50 dB or more, whereas when the spacing H was set to 40 mm and 50 mm (specimens 4 and 5 in Figure 5) or 5 mm (specimen 4 in Figure 6), the A-weighted sound pressure level was 40 dB or more. That is, under the condition 1, it was found that when the distance H was set to about 10 mm to 30 mm, the A-weighted sound pressure level tended to become large. (2) Also, as can be seen from Figure 6, even if the interval H is set to 5 mm under Condition 1, the fan air volume is 50 m3 as in the case of test specimens 4 to 7. 3 / h,60m 3 / h,70m 3 / h,75m 3It was found that the higher the setting (i.e., / h), the higher the A-weighted sound pressure level tends to be. In condition 1, the gap H is 5 mm and the fan air volume is 40 m 3 When the resistance was set to 0.1 V or less (see specimens 1 to 3), the A-weighted sound pressure level did not increase, just as in the case where no resistance device was provided (see specimen 6 in Figure 5). (3) In addition, as can be seen by comparing Figures 5 and 6, under Condition 1, the fan air volume was 50 m 3 When the spacing H is set to 30mm to 50mm, it can be seen that, in general, sounds in the low frequency range (80Hz to 1kHz) tend to become louder and sounds in the high frequency range (1kHz or higher) tend not to become louder; however, as the spacing H is reduced to 20mm, 10mm, etc., it can be seen that, conversely, sounds in the low frequency range (80Hz to 160Hz) tend to become quieter and sounds in the high frequency range (1kHz or higher) tend to become louder. Furthermore, as can be seen from FIG. 6, even if the gap H is set to 5 mm under condition 1, the fan air volume is 50 m 3 / h or more (test specimens 5 to 7), it was found that there was a tendency for the sound to become louder in certain bands above the 1 kHz band. (4) That is, under condition 1, the fan air volume is 50 m 3 When the interval H is set to / h, it was found that increasing the interval H tends to make the sound in the low frequency band louder, and conversely, decreasing the interval H tends to make the sound in a specific band in the high frequency band louder. Furthermore, in condition 1, the interval H is reduced and the fan air volume is increased to 50 m 3 / h or more, it was found that the greater the fan volume, the louder the sound in certain high frequency ranges tends to be.

[0043] The experimental results were verified under the condition that the diameter of the upwind hole 21 was 42.5 mm and the diameter of the downwind hole 31 was 47.5 mm, i.e., the diameter of the upwind hole was 5 mm smaller than the diameter of the downwind hole (hereinafter referred to as condition 2). (1) Under condition 2, as can be seen from FIG. 7, the fan air volume was 50 m3 / h and the interval H is 10 mm, the A-weighted sound pressure level does not increase compared to the case where the resistance device 1X is not provided (test piece 6 in Figure 5) or where only the windward hole 21 is provided (test piece 6). In addition, under condition 2, the fan air volume was 50 m 3 / h and the spacing H was set to 20 mm, 30 mm, 40 mm, and 50 mm, the A-weighted sound pressure level was 30 dB to 40 dB, which was found to be higher than when no resistance device was provided (test piece 6 in Figure 5) or when only a windward hole was provided (test piece 6). (2) In condition 2, the fan volume was 50 m 3 / h and the spacing H is 20mm to 50mm, the sound in the 250Hz to 315Hz band tends to get louder, and in particular, when the spacing H is 40mm or 50mm, the sound in the 250Hz band gets louder and the sound in the 100Hz to 125Hz band also tends to get louder. (3) In other words, under condition 2, the A-weighted sound pressure level is not higher than under condition 1, but by increasing the interval H, there is a tendency for the sounds in the 100 Hz to 125 Hz band and the 250 Hz band to be louder.

[0044] Experimental results verifying the effect of varying the difference in diameter between the upwind hole 21 and the downwind hole 31 (hereinafter referred to as condition 3). (1) In condition 3, as can be seen from Figure 8, when the upwind hole diameter is larger than the downwind hole diameter and the difference A between the upwind hole diameter and the downwind hole diameter is 2.5 mm to 7.5 mm (test specimens 3, 2, and 1), the A-weighted sound pressure level tends to increase as the difference A increases. Conversely, when the upwind hole diameter is smaller than the downwind hole diameter and the difference B between the upwind hole diameter and the downwind hole diameter is 2.5 mm to 7.5 mm (test specimens 5, 6, and 7), it was found that the A-weighted sound pressure level tends to decrease as the difference B increases. (2) Furthermore, in condition 3, as can be seen from Figure 9, when the upwind hole diameter is larger than the downwind hole diameter and the difference A between the upwind hole diameter and the downwind hole diameter is 2.5 mm to 7.5 mm (test specimens 3, 2, and 1), the A-weighted sound pressure level tends to increase as the difference A increases. Conversely, when the upwind hole diameter is smaller than the downwind hole diameter and the difference B between the upwind hole diameter and the downwind hole diameter is 2.5 mm to 7.5 mm (test specimens 5, 6, and 7), it was found that the A-weighted sound pressure level tends to decrease as the difference B increases. That is, the interval H is set to 30 mm, and the fan air volume is set to 40 m 3 / h or 50m 3 / h, it was found that the experimental results when the difference in diameter between the upwind hole 21 and the downwind hole 31 was varied showed a similar tendency. (3) Also, the spacing H is 30 mm and the fan volume is 40 m 3 / h or 50m 3 / h, as shown in test piece 4 in Figure 8 and test piece 4 in Figure 9, even when the upwind hole diameter and the downwind hole diameter are the same, the A-weighted sound pressure level tends to be large. (4) In addition, under condition 3, it was found that increasing the fan volume tended to result in a higher A-weighted sound pressure level. We also found that there is a tendency for sounds between 400 Hz and 1.6 kHz to be louder when the fan volume is increased. (5) From the above, it was found that the A-weighted sound pressure level becomes higher when the upwind hole diameter is larger than the downwind hole diameter, and that the A-weighted sound pressure level tends to become higher when the upwind hole diameter is larger than the downwind hole diameter and the difference A between the upwind hole diameter and the downwind hole diameter becomes larger. This is believed to be because, when the upwind hole diameter is larger than the downwind hole diameter, the wind passing through the upwind hole 21 collides with the resistance plate around the downwind hole 31, making it easier for noise to be generated.

[0045] The following can be seen from Experiments 1 to 5: First, as can be seen from the results of test specimen 4 in experiments 4 and 5, the diameter of the upwind hole 21 of the upwind side resistance device 2 and the diameter of the downwind hole 31 of the downwind side resistance device 3, which are opposed to each other, may be the same. Furthermore, as can be seen from the results of Experiments 1 to 5, when the diameter of the windward hole 21 of the upwind side resistance device 2 and the diameter of the downwind hole 31 of the downwind side resistance device 3 facing each other are made different, if the diameter of the upwind hole (through hole) 21 of the upwind side resistance device 2 is larger than the diameter of the downwind hole (through hole) 31 of the downwind side resistance device 3, the A-weighted sound pressure level tends to be large. In this case, it was found that if it is desired to increase the A-weighted sound pressure level, the difference A between the diameter of the upwind hole 21 and the diameter of the downwind hole 31 is preferably 2.5 mm or more. Furthermore, it was found that the distance between the windward hole (through hole) 21 of the windward-side resistance device 2 and the leeward hole (through hole) 31 of the leeward-side resistance device 3 is preferably 5 mm or more.

[0046] From the above experimental results, it has been demonstrated that, according to the resistance device 1X in embodiment 1, in which the number of upwind holes 21 of the upwind side resistance device 2 and the number of downwind holes 31 of the downwind side resistance device 3 are the same and the upwind holes 21 of the upwind side resistance device 2 and the downwind holes 31 of the downwind side resistance device 3 are configured to face each other one-to-one, it is possible to provide a background noise generating device in which the volume and pitch of the generated background noise can be adjusted by adjusting the distance H between the upwind holes 21 and the downwind holes 31, i.e., the distance between the upwind side resistance device 2 and the downwind side resistance device 3. It was also demonstrated that by making the diameter of the upwind hole 21 of the upwind side resistance device 2 and the diameter of the downwind hole 31 of the downwind side resistance device 3, which face each other in a one-to-one relationship, different, it is possible to provide a background noise generating device that can adjust the volume and pitch of the generated background noise. In other words, the level of masking processing (processing to cover up everyday sounds with background noise generated by the resistor device 1X) required varies depending on the purpose of the room, but according to embodiment 1, it is possible to provide a background noise generating device that can achieve masking processing appropriate for the purpose of the room. For example, in a place such as a bedroom, since the daily sounds (such as walking sounds) are about 30 dB, it is sufficient to provide a background noise generating device equipped with a resistor 1X that produces an A-weighted sound pressure level of about 30 dB to 35 dB. Additionally, in places where talking is a concern (rooms facing common corridors, corridors within residential buildings, etc.), masking should be done with a slightly louder sound of around 40 dB. In other words, in this case, a background noise generator equipped with resistor 1X that produces an A-weighted sound pressure level of around 40 dB should be installed. That is, a background noise generating device having a resistor device 1X capable of obtaining a masking effect according to the purpose of the room may be provided.

[0047] In addition, in a typical room, it is considered sufficient to provide a background noise generating device equipped with a resistor device 1X that produces an A-weighted sound pressure level of about 30 dB to 50 dB. However, for example, in a room with a high ceiling and very large size, it is necessary to generate a fairly loud sound in the vicinity of the air intake 1 (for example, in the above-mentioned experiment, at a position 1 m directly below the center position of the through hole formed in the ceiling model) so that the sound can reach every corner of the room. Therefore, in such a case, it is considered sufficient to provide a background noise generator equipped with a resistor 1X like the test specimen that achieved an A-weighted sound pressure level of 50 dB or more in the above-mentioned experiment. On the other hand, on the other hand, in the case of a small room such as a bedroom, it is considered sufficient to provide a background noise generator equipped with a resistor 1X that achieves an A-weighted sound pressure level in the room of about 30 dB, taking into account reflections in the room, etc. That is, the background noise generating device can be constructed by selecting the resistor device 1X that can realize masking processing according to the position of the air inlet 1, the size of the room, and the purpose of the room.

[0048] Furthermore, as can be seen from the experiment, the resistance device 1X makes it possible to select the magnitude of the sound pressure level for each frequency band and the frequency range in which the sound pressure level can be increased. That is, it is possible to select an appropriate resistance device 1X depending on the target sound source. For example, since everyday sounds such as walking sounds are relatively low-pitched sounds, a background noise generating device may be constructed by selecting a resistor device 1X capable of masking low-pitched sounds (for example, in the 125 Hz to 250 Hz band). Furthermore, when the target is speech, particularly for females, which has a high-pitched voice, a resistor device 1X capable of masking high-pitched voices (for example, in the 500 Hz to 1000 Hz band) may be selected to configure a background noise generating device. That is, according to the first embodiment, it is possible to configure a background noise generating device that can realize masking processing in accordance with the frequency characteristics of a target sound source.

[0049] EMBODIMENT 2 In embodiment 1, an upwind side resistance device 2 equipped with a cylindrical body 23 and a downwind side resistance device 3 equipped with a cylindrical body 33 are exemplified, but it is also possible for the upwind side resistance device 2 to not have a cylindrical body 23, and the downwind side resistance device 3 to not have a cylindrical body 33. In this case, the windward resistance device 2 and the leeward resistance device 3 may be fixedly installed inside the duct 16C so that the outer peripheral surface of the perforated circular plate 22 or the perforated circular plate 32 is in contact with or close to the inner peripheral surface 16U of the duct 16C. That is, the leeward resistance device 3 and the windward resistance device 2 may be configured to include a circular plate having an outer diameter corresponding to the inner diameter of the duct 16C and having upwind holes 21 and downwind holes 31 formed therein, and may be fixedly installed inside the duct 16C so that the outer circumferential surface of the perforated plate contacts or is close to the inner circumferential surface 16U of the duct 16C. In this case, for example, the outer circumferential side of the perforated plate may be provided with an attachment portion (claw or the like) not shown for the inner circumferential surface 16U of 16C, and the resistance plate may be directly attached to the inner surface of the duct via the attachment portion.

[0050] EMBODIMENT 3 Taking into consideration the experimental results described above, by using a resistance device 1X in which the upwind side resistance device 2 and the downwind side resistance device 3 are connected and the distance between the upwind side resistance device 2 and the downwind side resistance device 3 is made adjustable, it is possible to provide a background noise generating device in which the volume and pitch of the generated background noise can be adjusted by adjusting the distance between the upwind side resistance device 2 and the downwind side resistance device 3.

[0051] In the embodiment, an example has been shown in which the background noise generating device and the inside air intake hole 17 are provided on the ceiling, but the background noise generating device and the inside air intake hole 17 may be provided on the floor. In this case, the air supply means, heat exchange system, ducts, etc. are provided in the underfloor space, and the resistance device 1X is installed on the inside of the end of the duct 16C that is closer to the room 12. That is, the background noise generating device of the present invention can be installed in the space under the floor, and the volume of the sound generated when air flows into the room 12 through the background noise generating device can be increased.

[0052] In addition, the background noise generating device and the inside air intake hole 17 may be provided in a partition wall having an inner space. In this case, the duct, etc. may be provided in the inner space, and the resistance device 1X may be installed inside the end of the duct 16C that is closer to the room 12. That is, the background noise generating device of the present invention can be installed in an in-wall space, and the volume of the sound generated when air flows into the room 12 through the background noise generating device can be increased.

[0053] Also, a resistance device 1X may be provided in the duct 16B connected to the inside air intake hole 17 to form a background noise generating device.

[0054] A configuration without a heat exchange system may also be used. In this case, the forced air supply means and / or the forced exhaust means may not be provided. In such a case, an air supply fan may be installed at air supply hole 1 to supply air from outside the building through the attic space, underfloor space, and space within the walls into the room.

[0055] Also, in each embodiment, an example has been shown in which a background noise generating device is provided on the ceiling of each of multiple rooms in order to distribute the air taken into the building from outside to each of the multiple rooms in the building, but it is not necessarily required to have a configuration in which the air is distributed to each of multiple rooms in the building. In other words, it is sufficient to provide a background noise generating device on the ceiling, floor, or partition wall of one specific room in the building, and to increase the volume of the sound when air flows into the room through the background noise generating device.

[0056] The duct may have a cross-sectional shape other than a circular cross-section, for example, a rectangular cross-section, a triangular cross-section, or the like.

[0057] The material of the duct and the resistance device is not particularly limited, and may be, for example, a metal, a synthetic resin, or the like.

[0058] Furthermore, in each embodiment, an example has been shown in which the resistance device 1X is provided inside a duct such as duct 16C, but the resistance device 1X may be provided inside an air supply hole of air supply means 13. For example, the resistance device 1X may be provided inside a through hole formed in outer wall 9 of building 10, or inside an air supply hole constituted by a cylinder (corresponding to pipe 6 in Patent Document 1) that is attached inside the through hole and forms an outside air intake hole. In other words, the background noise generating device of the present invention may be a background noise generating device equipped with a resistance device 1X that provides resistance to the air passing through inside an air intake that functions as an air flow passage provided in a building to connect the outside of the building with the inside of the building. In other words, the background noise generating device of the present invention may be any background noise generating device that is equipped with the above-mentioned resistance device 1X in an air flow passage, such as a duct that leads air from outside the building to rooms within the building, or an air intake hole formed in the exterior wall 9 that leads air from outside the building to rooms within the building.

[0059] The cylinder of the air supply means 13, the cylindrical part 1A as the tubular part forming the air supply hole 1, and the cylinder of the exhaust means 15 described above do not necessarily have to be cylindrical, and may be, for example, a square cylinder or other cylindrical body. In addition, in the embodiment, a cylindrical part 1A with a step, which has a cylindrical portion at one opening end and a cylindrical portion at the other opening end that is smaller in diameter than the cylindrical portion at the one opening end, is exemplified as the cylindrical part that forms the air intake hole 1, but the cylindrical part that forms the air intake hole 1 may also be a cylindrical part without a step.

[0060] Furthermore, when a duct or cylinder that functions as an air flow passage is constructed of a duct formed with a cross-sectional shape other than a circular cross-section, or a cylinder other than a cylindrical body, the cylinder of the upwind side resistance device 2 and the cylinder of the downwind side resistance device 3 can be a cylinder of a shape corresponding to the cross-sectional shape of these ducts or cylinders.

[0061] In the embodiment, an example has been shown in which the upwind hole 21 and the downwind hole 31 are configured as circular through holes, but the upwind hole 21 and the downwind hole 31 may also be circular through holes such as elliptical, oval, and the like, or through holes having a rectangular, triangular, polygonal, irregular shape, and the like, formed in a plate having an outer diameter dimension corresponding to the inner diameter dimension of the duct 16C.

[0062] At least one of the centers 2C of the upwind hole 21 and 3C of the downwind hole 31, which face each other when installed in the air flow passage, may not be located on the center line of the air flow passage. In other words, the center 2C of the upwind hole 21 and the center 3C of the downwind hole 31, which face each other when installed in the air flow passage, may be misaligned.

[0063] Furthermore, the number of pairs of holes, each consisting of an upwind hole 21 and a downwind hole 31 that face each other in a one-to-one relationship when installed in the air flow passage, is not limited to one, and a plurality of pairs may be provided. That is, the resistance device 1X may be configured to have a plurality of pairs of holes, each pair being made up of an upwind hole 21 and a downwind hole 31 that face each other in a one-to-one relationship when the resistance device 1X is installed in the air flow passage.

[0064] The resistance device may be one that is molded as a single unit using a 3D (three-dimensional) printer or the like.

[0065] In addition, in the embodiment, an apartment building or other collective housing unit is exemplified as a building, but the present invention is also applicable to detached houses, hotels, offices, and other buildings. [Explanation of symbols]

[0066] 1 Air intake, 1X resistance device, 2 Upwind resistance device, 3 Downwind resistance device, 10 Building, 12 Room, 16C Duct (air passage), 21 Windward hole (through hole), 22 Circular plate with holes (resistance plate), 31 Downwind hole (through hole), 32 Circular plate with holes (resistance plate).

Claims

1. a duct provided in a ceiling space, an underfloor space, or an in-wall space of the building to communicate an air supply means provided on an outer wall of the building for taking in outside air from the outside of the building into the building with a room in the building; a resistance device provided on the inside of the duct on the side closer to the room to provide resistance when air passes through the inside of the duct; The resistance device is A leeward resistance device installed in the duct near the room; a windward resistance device installed in the duct at a position farther from the room than the downwind resistance device, The windward resistance device and the leeward resistance device each have a resistance plate with an outer diameter corresponding to the inner diameter of the duct and a through hole formed therein for allowing air to flow, and these resistance plates are installed inside the duct, in a background noise generating device, A background noise generating device characterized in that the number of through holes in the upwind resistance device and the number of through holes in the downwind resistance device are the same, and the through holes in the upwind resistance device and the through holes in the downwind resistance device are configured to face each other one-to-one.

2. 2. The background noise generating device according to claim 1, wherein the diameter of the through hole of the upwind resistance device and the diameter of the through hole of the downwind resistance device facing each other are different.

3. 3. A background noise generating device according to claim 2, wherein the diameter of the through hole of the windward resistance device is larger than the diameter of the through hole of the leeward resistance device.

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