Sound absorption structure, acoustic system, and vehicle

Abstract

To provide a technology of improving sound environment in a cabin of a vehicle while minimizing adverse effects on functions and design of components that make up the vehicle.SOLUTION: A sound absorption structure 10 installed in a vehicle equipped with a light-transmissive translucent plate comprises: a first face member 20 that is divided into an opening area corresponding to an opening and a non-opening area not corresponding to the opening and has light transmissivity; a second face member 30 facing the first face member by a gap and having light transmissivity; a side wall member 40 intervening between the first face member and the second face member, so that spaces divided by the first face member, the second face member, and the side wall member function as resonators 11-14. The resonator is divided by a portion of the first face member corresponding to the opening area and a portion corresponding to the non-opening area, the opening area is not centered on the non-opening area, and the sound absorption structure is installed in the vehicle such that the first face member faces interior space of the vehicle.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to sound absorbing structures, acoustic systems, and vehicles. [Background technology]

[0002] Reducing noise inside the vehicle cabin is expected to improve the riding experience for vehicle occupants. Patent Document 1 discloses a technical idea of ​​installing a sound absorbing structure in a vehicle cabin with the aim of suppressing standing waves and improving the sound environment. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-015207 Summary of the Invention [Problem to be solved by the invention]

[0004] It is expected that noise inside the vehicle cabin can be effectively reduced by providing a sound absorbing structure in a part of the vehicle body (e.g., window glass) made of a material with a low sound absorption rate (in other words, a high sound reflection rate). However, providing a sound absorbing structure may impair the function (e.g., light transmission function) or design of the material that constitutes the installation location.

[0005] An object of the present disclosure is to provide a technology that improves the sound environment within a vehicle cabin while minimizing adverse effects on the functionality and design of components that constitute the vehicle. [Means for solving the problem]

[0006] A sound absorbing structure according to one embodiment of the present disclosure is a sound absorbing structure provided in a vehicle having a light-transmitting plate. The sound absorbing structure includes a first surface member that is divided into an opening region corresponding to an opening and a non-opening region not corresponding to an opening and that is light-transmitting, a second surface member that faces the first surface member across a gap and is light-transmitting, and a sidewall member that is interposed between the first surface member and the second surface member, the space defined by the first surface member, the second surface member, and the sidewall member functions as a resonator, the resonator is defined by a portion of the first surface member that corresponds to the opening region and a portion that corresponds to the non-opening region, the opening region is not located at the center of the non-opening region, and the sound absorbing structure is provided in the vehicle such that the first surface member faces the interior space of the vehicle and at least a part of the light that passes through the light-transmitting plate passes through the first surface member. [Brief description of the drawings]

[0007] [Figure 1] FIG. 2 is a front view of the sound absorbing structure of the present embodiment. [Diagram 2] FIG. 2 is a perspective view of the sound absorbing structure of the present embodiment. [Diagram 3] FIG. 2 is a perspective view of a resonator that constitutes the sound absorbing structure of the present embodiment. [Figure 4] FIG. 2 is a perspective view of a resonator that constitutes the sound absorbing structure of the present embodiment. [Diagram 5] FIG. 2 is a perspective view of a resonator that constitutes the sound absorbing structure of the present embodiment. [Figure 6] FIG. 2 is a perspective view of a resonator that constitutes the sound absorbing structure of the present embodiment. [Figure 7] 1A to 1C are diagrams illustrating an example of installation of the sound absorbing structure of the present embodiment. [Figure 8] 1 is a view of a vehicle interior in which the sound absorbing structure of this embodiment is installed, viewed from the SL direction and the U direction. [Figure 9] 1 is a diagram conceptually showing standing waves that occur in a vehicle cabin when the sound absorbing structure of this embodiment is not installed. FIG. [Figure 10] 1 is a diagram conceptually showing standing waves that occur in a vehicle cabin when the sound absorbing structure of this embodiment is installed. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the drawings for explaining the embodiment, the same components are generally designated by the same reference numerals, and the repeated description will be omitted.

[0009] (1) Sound absorbing structure configuration (1-1) Basic structure of sound absorbing structure The basic configuration of the sound absorbing structure of this embodiment will be described. Fig. 1 is a front view of the sound absorbing structure of this embodiment. Fig. 2 is a perspective view of the sound absorbing structure of this embodiment. Fig. 3 is a perspective view of a resonator constituting the sound absorbing structure of this embodiment. Fig. 4 is a perspective view of a resonator constituting the sound absorbing structure of this embodiment. Fig. 5 is a perspective view of a resonator constituting the sound absorbing structure of this embodiment. Fig. 6 is a perspective view of a resonator constituting the sound absorbing structure of this embodiment.

[0010] The sound-absorbing structure of this embodiment is a sound-absorbing member equipped with a specific sound-absorbing structure that has a sound-absorbing effect of reducing the sound pressure of reflected sound and transmitted sound by converting the energy of sound waves traveling toward the front of the sound-absorbing structure into other energy or canceling it out.

[0011] In the following description, the "D direction" is the depth direction (thickness direction) of the sound absorbing structure. The sound absorbing structure mainly absorbs sound waves traveling in the D direction. The front of the sound absorbing structure means the surface of the sound absorbing structure in the -D direction. The "H direction" is a direction substantially perpendicular to the D direction, and is the height direction of the sound absorbing structure. The "W direction" is a direction perpendicular to the "D direction" and the "H direction", and is the width direction of the sound absorbing structure. The sound absorbing structure has one or more cavities (hereinafter referred to as "resonance spaces") into which sound waves can enter through perforations, and each resonance space functions as a resonator. The shape of the resonance space is arbitrary. For example, the sound absorbing structure may have a box-shaped resonance space, a tubular resonance space, or a resonance space in the shape of a bent tube.

[0012] 1 and 2, the sound absorbing structure 10 includes a first surface member 20, a second surface member 30, and a side wall member 40. The distinction between the first surface member 20, the second surface member 30, and the side wall member 40 is for convenience, and some or all of these members may be integrated, at least one member may be subdivided, or the subdivided member may be integrated with another member. As an example, the second surface member 30 and the side wall member 40 may be configured as an integrated part.

[0013] The first surface member 20 constitutes the surface on the -D direction side of the sound absorbing structure 10 (i.e., the front side). The first surface member 20 is divided into an opening region corresponding to an opening and a non-opening region not corresponding to an opening. The first surface member 20 has one or more opening regions for each resonator (resonance space) included in the sound absorbing structure 10. In the opening region, a plurality of perforations penetrating the first surface member in the D direction are densely formed. The inside and outside of each resonance space are connected via the plurality of perforations present in the opening region, and ventilation is possible. In other words, the inside and outside of each resonance space are blocked (not ventilation is possible) by each member that partitions the resonance space, except for the opening region. The first surface member 20 is optically transparent.

[0014] The second surface member 30 is disposed opposite the first surface member 20 across a gap in the D+ direction, and constitutes the +D direction side surface (i.e., the back surface) of the sound absorbing structure 10. The second surface member 30 is optically transparent.

[0015] The side wall member 40 is interposed between the first surface member 20 and the second surface member 30, thereby dividing the gap between the first surface member 20 and the second surface member 30 into one or more resonance spaces. The side wall member 40 is optically transparent.

[0016] In other words, the space defined by the first surface member 20, the second surface member 30, and the side wall member 40 functions as a resonator (resonance space). In the example of Fig. 1 and Fig. 2, the sound absorbing structure 10 corresponds to a configuration in which six sound absorbing units, each of which is made up of a resonator 11, a resonator 12, a resonator 13, and a resonator 14 connected along the H direction, are connected in the W direction.

[0017] The opening areas of the resonators 11 to 14 are exposed when viewed from the -D direction. Sound waves arriving from the -D direction with respect to the sound absorbing structure 10 and entering each opening area enter the inside of each resonance space through a plurality of perforations formed in the opening area, proceed through the portion covered by the non-opening area non-parallel to the D direction, and are reflected by the side surface of the side wall member 40. Each opening area functions as an acoustic impedance matching member, and the resonators 11 to 14 function as resonators having different resonance characteristics (sound absorbing characteristics). Therefore, the sound absorbing structure 10 can obtain a sound absorbing effect in a wide frequency band compared to a sound absorbing material having a single resonator. The sound absorbing characteristics of the sound absorbing structure 10 in this embodiment are represented by, for example, the sound absorption coefficient for each frequency or the acoustic impedance. The sound absorbing structure 10 may be designed so that the frequency bands of the sound waves absorbed by each resonator do not overlap with each other, or the sound absorbing structure 10 may be designed so that the frequency bands of the sound waves absorbed by each resonator overlap with each other.

[0018] The sound absorbing structure 10 can be made of various materials since it exhibits sound absorbing performance depending on its shape and structure. The sound absorbing structure 10 is made of materials such as glass or resin (acrylic as an example) having transparency. However, the sound absorbing structure 10 may be made of materials other than these materials. The sound absorbing structure 10 may also be made by combining a plurality of members each made of different materials. For example, the first surface member 20, the second surface member 30, and the side wall member 40 of the sound absorbing structure 10 may be made of different materials (for example, materials with different light transmittance).

[0019] 3, the resonator 11 includes a member 21 that is a part of the first surface member 20, a member 31 that is a part of the second surface member 30, and members 41a, 41b, 41c, 41d, 41e, and 41f that are parts of the sidewall member 40. The resonator 11 forms a tubular cavity and functions as a waveguide.

[0020] The member 21 is divided into an opening region 21h and a non-opening region that occupies the rest. The opening region 21h is not located at the center of the non-opening region of the member 21. In the example of Fig. 3, the opening region 21h is located at a corner that corresponds to the -W direction end and the +H direction end of the member 21. This lengthens the path that the sound wave that enters the resonator 11 through the opening region 21h takes to be reflected at the end of the waveguide, thereby lowering the resonance frequency of the resonator 11. The member 21 forms the -D direction surface of the resonator 11.

[0021] The member 31 is disposed opposite the member 21 across a gap in the D+ direction, and constitutes the surface of the resonator 11 in the +D direction.

[0022] The member 41a connects the end of the member 21 facing the +H direction and the end of the member 31 facing the +H direction, and constitutes the surface of the resonator 11 facing the +H direction.

[0023] Member 41b connects the +W direction end of member 21 and the +W direction end of member 31, and constitutes the +W direction surface of resonator 11. Member 41b may also be used as member 41d of resonator 11 included in another sound absorbing unit adjacent in the +W direction.

[0024] The member 41c connects the -H direction end of the member 21 and the -H direction end of the member 31, and constitutes the -H direction surface of the resonator 11. The member 41c may also be used as a member (member 42a described later) that constitutes the resonator 12 adjacent to the resonator 11 in the -H direction.

[0025] The member 41d connects the -W direction end of the member 21 and the -W direction end of the member 31, and constitutes the -W direction surface of the resonator. The member 41d may be used in combination with the member 41b of another resonator 11 included in another sound absorbing unit adjacent to the resonator 11 in the -W direction.

[0026] The members 41e and 41f can also be called partition plates. The members 41e and 41f bend the path (i.e., the waveguide) along which the sound waves incident on the resonator 11 are transmitted, thereby lengthening the path without increasing the dimensions in the H and W directions. This allows the resonator 11 to resonate at a lower frequency. The members 41e and 41f also have the effect of increasing the rigidity of the resonator 11.

[0027] For the purpose of lowering the resonance frequency of the resonator 11, increasing the rigidity of the resonator 11, or both, members such as members 41e and 41f that connect the members 21 and 31 mainly inside the resonator 11 can be added. Similar modifications are possible for other resonators.

[0028] As shown in FIG. 4, the resonator 12 includes a member 22 that is part of the first surface member 20, a member 32 that is part of the second surface member 30, and members 42a, 42b, 42c, 42d, and 42e that are part of the side wall member 40.

[0029] The member 22 is divided into an opening region 22h and a non-opening region that occupies the rest. The opening region 22h is not located at the center of the non-opening region of the member 22. In the example of FIG. 4, the opening region 22h is located at a corner that corresponds to the -W direction end and the +H direction end of the member 22. This lengthens the path that the sound wave that enters the resonator 12 through the opening region 22h takes until it is reflected, and the resonance frequency of the resonator 11 can be lowered. The member 22 forms the -D direction surface of the resonator 12.

[0030] The member 32 is disposed opposite the member 22 across a gap in the D+ direction, and constitutes the surface of the resonator 12 in the +D direction.

[0031] The member 42a connects the +H direction end of the member 22 and the +H direction end of the member 32, and constitutes the +H direction surface of the resonator 12. The member 42a may also be used as the member 41c of the resonator 11 adjacent to the resonator 12 in the +H direction.

[0032] The member 42b connects the +W direction end of the member 22 and the +W direction end of the member 32, and constitutes the +W direction surface of the resonator 12. The member 42b may also be used as a member 42d of another resonator 12 included in another sound absorbing unit adjacent to the resonator 12 in the +W direction.

[0033] The member 42c connects the -H direction end of the member 22 and the -H direction end of the member 32, and constitutes the -H direction surface of the resonator 12. The member 42c may also be used as a member (member 43a described later) constituting the resonator 13 adjacent to the resonator 12 in the -H direction.

[0034] The member 42d connects the -W direction end of the member 22 and the -W direction end of the member 32, and constitutes the -W direction surface of the resonator. The member 42d may be used in combination with the member 42b of another resonator 12 included in another sound absorbing unit adjacent to the resonator 12 in the -W direction.

[0035] The member 42e can also be called a partition plate. The member 42e bends the path of the sound wave that enters the resonator 12 until it is reflected, thereby lengthening the path without increasing the dimensions in the H and W directions. This allows the resonator 12 to resonate at a lower frequency. The member 42e also has the effect of increasing the rigidity of the resonator 12.

[0036] As shown in FIG. 5, the resonator 13 includes a member 23 which is a part of the first surface member 20, a member 33 which is a part of the second surface member 30, and members 43a, 43b, 43c, and 43d which are parts of the sidewall member 40.

[0037] The member 23 is divided into an opening region 23h and a non-opening region that occupies the rest. The opening region 23h is not located at the center of the non-opening region of the member 23. In the example of Fig. 5, the opening region 23h is located at a corner that corresponds to the -W direction end and the +H direction end of the member 23. This lengthens the path that the sound wave that enters the resonator 13 through the opening region 23h takes to be reflected, thereby lowering the resonance frequency of the resonator 11. The member 23 forms the -D direction surface of the resonator 13.

[0038] The member 33 is disposed opposite the member 23 across a gap in the D+ direction, and constitutes the surface of the resonator 13 in the +D direction.

[0039] The member 43a connects the +H direction end of the member 23 and the +H direction end of the member 33, and constitutes the +H direction surface of the resonator 13. The member 43a may also be used as the member 42c of the resonator 12 adjacent to the resonator 13 in the +H direction.

[0040] The member 43b connects the +W direction end of the member 23 and the +W direction end of the member 33, and constitutes the +W direction surface of the resonator 13. The member 43b may also be used as a member 43d of another resonator 13 included in another sound absorbing unit adjacent to the resonator 13 in the +W direction.

[0041] The member 43c connects the -H direction end of the member 23 and the -H direction end of the member 33, and constitutes the -H direction surface of the resonator 13. The member 43c may also be used as a member (member 44a described later) constituting the resonator 14 adjacent to the resonator 13 in the -H direction.

[0042] The member 43d connects the -W direction end of the member 23 and the -W direction end of the member 33, and constitutes the -W direction surface of the resonator. The member 43d may be used in combination with the member 43b of another resonator 13 included in another sound absorbing unit adjacent to the resonator 13 in the -W direction.

[0043] As shown in FIG. 6, the resonator 14 includes a member 24 that is part of the first surface member 20, a member 34 that is part of the second surface member 30, and members 44a, 44b, 44c, and 44d that are parts of the sidewall member 40.

[0044] The member 24 is divided into an opening region 24h and a non-opening region that occupies the rest. The opening region 24h is not located at the center of the non-opening region of the member 24. In the example of Fig. 6, the opening region 24h is located on the side corresponding to the end in the -W direction of the member 24. This lengthens the path that the sound wave that enters the resonator 14 through the opening region 24h takes to be reflected, thereby lowering the resonance frequency of the resonator 11. The member 24 forms the surface of the resonator 14 in the -D direction.

[0045] The member 34 is disposed opposite the member 24 across a gap in the D+ direction, and constitutes the +D direction surface of the resonator 14.

[0046] The member 44a connects the +H direction end of the member 24 and the +H direction end of the member 34, and constitutes the +H direction surface of the resonator 14. The member 44a may also be used as the member 43c of the resonator 13 adjacent to the resonator 14 in the +H direction.

[0047] The member 44b connects the +W direction end of the member 24 and the +W direction end of the member 34, and constitutes the +W direction surface of the resonator 14. The member 44b may also be used as a member 44d of another resonator 14 included in another sound absorbing unit adjacent to the resonator 14 in the +W direction.

[0048] The member 44c connects the end of the member 24 facing the -H direction and the end of the member 34 facing the -H direction, and constitutes the surface of the resonator 14 facing the -H direction.

[0049] The member 44d connects the -W direction end of the member 24 and the -W direction end of the member 34, and constitutes the -W direction surface of the resonator. The member 44d may be used in combination with the member 44b of another resonator 14 included in another sound absorbing unit adjacent to the resonator 14 in the -W direction.

[0050] (1-2) Configuration of the first surface member The configuration of the first surface member 20 will be described. A plurality of perforations are densely formed in the opening region 21h, the opening region 22h, the opening region 23h, and the opening region 24h of the first surface member 20. The first surface member 20 may be configured as a single unit, or may be configured by combining a plurality of members. For example, the portion of the first surface member 20 that covers the surface in the -D direction of each resonance space may be configured with a separate member, or each opening region and each non-opening region of the first surface member 20 may be configured with a separate member. By configuring the entire first surface member 20 as a single unit, the manufacturing process of the first surface member 20 can be simplified, and the manufacturing cost can be reduced. On the other hand, by configuring the first surface member 20 by combining a plurality of members, the size of each member can be reduced, so that a large first surface member 20 can be created even if there is a limit to the manufacturable size of the member.

[0051] The resonance characteristics of each resonator depend on the shape of the resonator (resonance space) and the shape parameters (hereinafter referred to as "hole parameters") of the first surface member combined with the resonator. The hole parameters include, for example, the following: Area of ​​the open area (area of ​​the surface on which the holes are formed) -Thickness of the first surface part (dimension perpendicular to the surface) Hole size (e.g. diameter if the hole is circular) The ratio of the area of ​​holes to the surface of the first surface member (hereinafter referred to as "hole occupancy rate") Hole shape Number of holes Hole spacing

[0052] By changing the hole parameters of the first surface member, it is possible to adjust the acoustic impedance of the sound absorbing structure 10. In addition, the multiple perforations formed in the first surface member 20 have the effect of lowering the Q value by thermoviscous resistance, thereby enabling sound absorption over a wide frequency band.

[0053] The hole parameters of the multiple opening regions of the sound absorbing structure 10 may be different from each other. For example, the hole parameters of the opening region 21h may be optimized according to the sound absorbing characteristics required for the resonator 11. The hole parameters of the opening region 22h may be optimized according to the sound absorbing characteristics required for the resonator 12. The hole parameters of the opening region 23h may be optimized according to the sound absorbing characteristics required for the resonator 13. The hole parameters of the opening region 24h may be optimized according to the sound absorbing characteristics required for the resonator 14. That is, the multiple perforations that communicate the inside and outside of one of the resonators 11 to 14 and the multiple perforations that communicate the inside and outside of the other resonators may differ in at least one of the hole parameters or the arrangement of the holes. This allows the sound absorbing structure 10 to achieve a high sound absorption coefficient in a wide frequency band. However, this is not limited to this, and the hole parameters of the multiple opening regions of the sound absorbing structure 10 may be common. This allows the specifications of the holes in the first surface member 20 to be unified, thereby reducing the manufacturing cost of the first surface member 20.

[0054] In the example of the sound absorbing structure 10, the surface of the first surface member 20 is flat, but the shape of the first surface member 20 is not limited to this. For example, the surface of the first surface member 20 may be curved or may have irregularities.

[0055] (2) Application examples of sound absorbing structures An application example of the sound absorbing structure of this embodiment will be described. Fig. 7 is a diagram showing an installation example of the sound absorbing structure of this embodiment. Fig. 8(a) is a diagram showing the vehicle cabin in which the sound absorbing structure of this embodiment is installed, viewed from the SL direction. Fig. 8(b) is a diagram showing the vehicle cabin in which the sound absorbing structure of this embodiment is installed, viewed from the U direction. Fig. 9 is a diagram conceptually showing standing waves that occur in the vehicle cabin when the sound absorbing structure of this embodiment is not installed. Fig. 10 is a diagram conceptually showing standing waves that occur in the vehicle cabin when the sound absorbing structure of this embodiment is installed.

[0056] In the following explanation, the upward (U direction), downward (D direction), forward (F direction), backward (R direction), leftward (SL direction), and rightward (SR direction) are defined with reference to a vehicle in a specified posture.

[0057] The vehicle 100 of this embodiment may be any of a gasoline vehicle, a hybrid vehicle, and an electric vehicle. The vehicle 100 may or may not have an automatic driving function. The vehicle 100 includes the sound absorbing structure 10 of this embodiment and a vehicle body 101. In addition, the vehicle 100 may include basic vehicle components such as a chassis, an engine (or a motor), a fuel tank (or a battery), a drive train, or a speaker (car audio). In this manner, the sound absorbing structure 10 is provided in the vehicle 100. Specifically, as shown in FIG. 7, the vehicle body 101 includes a light-transmitting plate 101a, and the sound absorbing structure 10 is provided so as to cover the light-transmitting plate 101a. That is, the sound absorbing structure 10 is provided in the vehicle 100 so that the first surface member 20 faces the interior space of the vehicle and the second surface member 30 faces the light-transmitting plate 101a. For example, an attachment means may be provided on the back surface of the second surface member 30 (i.e., the surface in the +D direction), and the sound absorbing structure 10 may be installed by attaching the second surface member 30 to the light-transmitting plate 101a using the attachment means. As the attachment means, for example, adhesive, double-sided tape, hook-and-loop fastener, magnet, suction cup, screw fastener, or other fastening means may be used. The attachment means may attach the sound absorbing structure 10 in a detachable manner, or may permanently fix the sound absorbing structure 10. The attachment means may be made of a light-transmitting material.

[0058] The sound absorbing structure 10 may completely or partially cover the light-transmitting plate 101a. Furthermore, the sound absorbing structure 10 may cover a portion of the vehicle body 101 other than the light-transmitting plate 101a in addition to at least a portion of the light-transmitting plate 101a.

[0059] The light-transmitting plate 101a is a transparent or semi-transparent member that separates the interior space of the vehicle 100 (i.e., the vehicle cabin) from the outside of the vehicle 100. The light-transmitting plate 101a may be made of, for example, glass or resin (acrylic as an example). Through the light-transmitting plate 101a, the occupants of the vehicle 100 can see the outside of the vehicle 100 from the vehicle cabin. Depending on the arrangement of the light-transmitting plate 101a, a person outside the vehicle 100 may be able to see the inside of the vehicle cabin through the light-transmitting plate 101a. The light-transmitting plate 101a may be arranged on at least one of the walls, ceiling, or floor of the vehicle cabin on the front, rear, left, or right sides.

[0060] In order to effectively attenuate standing waves occurring in the cabin of the vehicle 100, the sound absorbing structure 10 may be designed to have sound absorbing characteristics according to a peak-dip frequency that depends on the dimensions or shape of the cabin, the reflectance of the members (interior materials) that constitute the cabin, or the position of the speaker mounted in the vehicle 100. Specifically, as shown in FIG. 8(a) and FIG. 8(b), the cabin length, the cabin width, and the cabin height of the vehicle 100 are assumed to be l, w, and h, respectively. The cabin length is the distance between the wall in the front (F) direction of the cabin and the wall in the rear (R) direction of the cabin. The cabin width is the distance between the wall in the left (SL) direction of the cabin and the wall in the right (SR) direction of the cabin. The cabin height is the distance between the wall in the upper (U) direction of the cabin and the wall in the lower (D) direction of the cabin. The position and orientation of the speaker depend on the design of the vehicle 100, but may be arranged, for example, on any of the front, rear, left, right, or right walls, floor, or ceiling of the cabin, facing the center of the cabin.

[0061] The frequency of the first standing wave that occurs mainly in the front-to-back (FB) direction of the vehicle cabin corresponds to a wavelength twice the length of the cabin length l. In other words, the frequency fl of the nth standing wave that occurs mainly in the front-to-back (FB) direction of the vehicle cabin can be expressed by the following formula. fl = (n × c) / (l × 2) (1) Here, c is the sound speed, and n is the order of the standing wave (i.e., an integer of 1 or more). The sound speed depends on the temperature of the medium, but can be considered to be approximately 340 [m / s] at room temperature. In short, by designing the sound absorbing structure 10 so that the resonance frequency f (which corresponds to one of the frequencies at which the sound absorption coefficient of the sound absorbing structure is maximized) of at least one resonator constituting the sound absorbing structure 10 is in the range of about (n×340) / (l×2), for example, (n×340) / (l×5 / 2) < f < (n×340) / (l×3 / 2), the n-th order standing wave generated mainly in the front-rear (FB) direction of the vehicle cabin can be effectively absorbed. In this case, the sound absorbing structure 10 can be installed so as to cover the transparent plate 101a arranged on either the wall in the front (F) direction or the wall in the rear (R) direction of the vehicle cabin, thereby further enhancing the sound absorbing effect of the standing wave generated mainly in the front-rear (FB) direction of the vehicle cabin. A plurality of resonators included in the sound absorbing structure may be assigned resonant frequencies corresponding to different n.

[0062] The frequency of the first standing wave that occurs mainly in the left-right (SL-SR) direction in the vehicle cabin corresponds to a wavelength twice the length of the vehicle cabin w. In other words, the frequency fw of the nth standing wave that occurs mainly in the left-right (SL-SR) direction in the vehicle cabin can be expressed by the following formula. fw = (n × c) / (w × 2) (2) In short, by designing the sound absorbing structure 10 so that the resonance frequency f of at least one resonator constituting the sound absorbing structure 10 is in the range of about (n×340) / (w×2), for example, (n×340) / (w×5 / 2) < f < (n×340) / (w×3 / 2), it is possible to effectively absorb n-th order standing waves occurring mainly in the left-right (SL-SR) direction of the vehicle cabin. In this case, the sound absorbing structure 10 is installed so as to cover the light-transmitting plate 101a arranged on either the left (SL) or right (SR) wall of the vehicle cabin, thereby further enhancing the sound absorbing effect of standing waves occurring mainly in the left-right (SL-SR) direction of the vehicle cabin. Resonance frequencies corresponding to different n may be assigned to multiple resonators included in the sound absorbing structure.

[0063] The frequency of the first standing wave that occurs mainly in the vertical (UD) direction in the vehicle cabin corresponds to a wavelength twice the length of the cabin height (h). In other words, the frequency fh of the nth standing wave that occurs mainly in the vertical (UD) direction in the vehicle cabin can be expressed by the following formula. fh = (n × c) / (h × 2) (3) In short, by designing the sound absorbing structure 10 so that the resonance frequency f of at least one resonator constituting the sound absorbing structure 10 is in the range of about (n×340) / (h×2), for example, (n×340) / (h×5 / 2) < f < (n×340) / (h×3 / 2), it is possible to effectively absorb n-th order standing waves occurring mainly in the up-down (UD) direction of the vehicle cabin. In this case, the sound absorbing structure 10 can be installed so as to cover the transparent plate 101a arranged on either the upper (U) or lower (D) wall of the vehicle cabin, thereby further enhancing the sound absorbing effect of standing waves occurring mainly in the up-down (UD) direction of the vehicle cabin. Resonance frequencies corresponding to different n may be assigned to multiple resonators included in the sound absorbing structure.

[0064] For example, when the sound absorbing structure 10 is not installed, a standing wave SW1 is generated in the vehicle cabin as shown in FIG. 9. Depending on the height of the occupant, the height of the seat, the height of the ceiling of the vehicle cabin, and the like, the ear of the occupant may be located near the antinode of the standing wave SW1 when the occupant is seated in the seat. Specifically, when a sound is measured at the assumed position of the occupant's ear, a peak (dip) due to the standing wave SW1 appears in the frequency characteristics of the sound. This means that when the occupant's ear is near the measurement point, the volume of the standing wave SW1 is large, and the occupant may experience a distorted waveform of the sound (e.g., music, car radio, video sound, etc.) emitted from a speaker (not shown) mounted on the vehicle 100 (deterioration in original sound reproduction), and may have difficulty in hearing the voices of other occupants.

[0065] On the other hand, as shown in FIG. 10, it is assumed that the sound absorbing structure 10 is installed in the vehicle cabin. Each resonator included in the sound absorbing structure 10 absorbs the frequency components of the standing wave SW2 generated in the vehicle cabin according to the shape (e.g., length or volume) of the resonator and the hole parameters of the first surface member 20. As a result, the standing wave SW2 is significantly reduced compared to the case where the sound absorbing structure 10 is not installed. That is, the peak due to the standing wave SW2 is suppressed. Therefore, the volume of the standing wave SW2 at the ears of the occupants is reduced, and the occupants can reduce the distortion of the sound radiated from the speaker (not shown) mounted on the vehicle 100 (improvement of the reproduction of the original sound) and can easily hear the voices of other occupants. That is, the sound environment in the vehicle cabin is improved. In particular, when the vehicle 100 is an electric vehicle, the occupants can easily perceive low-frequency road noise because there is no engine noise compared to a gasoline vehicle, so the benefit of the improvement of the sound environment in the vehicle cabin is great. In addition, if the vehicle 100 is an autonomous vehicle, the driver may place more importance on the viewing experience of content such as music and videos than if the vehicle 100 is not autonomous, and the benefit of improving the sound environment in the vehicle cabin is greater.

[0066] Furthermore, since the sound absorbing structure 10 is composed of the first surface member 20, the second surface member 30, and the side wall member 40, each of which has optical transparency, even if the sound absorbing structure 10 is installed so as to cover the light-transmitting plate 101a, at least a part of the light passing through the light-transmitting plate 101a passes through the first surface member 20. Therefore, the functions (light intake, visibility of the outside world from the vehicle interior, visibility of the inside of the vehicle interior from the outside world, etc.) and design of the light-transmitting plate 101a are hardly impaired.

[0067] Furthermore, some of the resonators constituting the sound-absorbing structure 10 may be configured to resonate in the frequency bands used for human speech and music. This suppresses the sound emitted from a speaker (not shown) mounted on the vehicle 100 and the speech of other passengers from reverberating inside the vehicle cabin, allowing passengers to hear these sounds more clearly.

[0068] The acoustic system of this embodiment can be constructed by combining the sound absorbing structure 10 of this embodiment with a speaker that radiates sound that propagates into the interior space of the vehicle 100 (i.e., a speaker mounted on the vehicle 100).

[0069] (3) Summary As described above, the sound absorbing structure 10 of this embodiment is provided on a vehicle 100 equipped with a light-transmitting plate 101a having optical transparency. The sound absorbing structure 10 includes a first surface member 20 that is divided into an opening region corresponding to an opening and a non-opening region not corresponding to an opening and has optical transparency, a second surface member 30 that faces the first surface member 20 across a gap and has optical transparency, and a sidewall member 40 that is interposed between the first surface member 20 and the second surface member 30. In the sound absorbing structure 10, a space defined by the first surface member 20, the second surface member 30, and the sidewall member 40 functions as a resonator, and the resonator is defined by a portion of the first surface member 20 that corresponds to the opening region and a portion that corresponds to the non-opening region, and the opening region is not located at the center of the non-opening region. The sound absorbing structure 10 is provided on the vehicle 100 such that the first surface member 20 faces the interior space of the vehicle 100 and at least a portion of the light passing through the light-transmitting plate 101a passes through the first surface member 20. This allows the sound absorbing structure 10 to suppress standing waves and sound reverberation in the cabin of the vehicle 100 and improve the sound environment. Furthermore, since the sound absorbing structure 10 is composed of the first surface member 20, the second surface member 30, and the side wall member 40, each of which has optical transparency, even if the sound absorbing structure 10 is provided so as to cover the light-transmitting plate 101a, the function and design of the light-transmitting plate 101a are hardly impaired.

[0070] The light-transmitting plate 101a may be a transparent or semi-transparent member that separates the interior space of the vehicle 100 from the outside of the vehicle 100. This makes it possible to improve the sound environment in the vehicle cabin while maintaining the functions of the light-transmitting plate 101a, such as taking in light, providing good visibility of the outside world from the vehicle cabin, and providing good visibility from the outside world to the inside of the vehicle cabin.

[0071] Each of the open regions may have a plurality of perforations densely formed therein, which can reduce the deviation of the sound absorption coefficient according to frequency (i.e., make the peak of the sound absorption characteristic gentler).

[0072] If the frequency at which the sound absorption coefficient of the sound absorbing structure 10 is maximized is f, the interior length, width, and height of the vehicle 100 are l, w, and h, respectively, and n is an integer equal to or greater than 1, the frequency f may satisfy at least one of (n×340) / (l×5 / 2) < f < (n×340) / (l×3 / 2), (n×340) / (w×5 / 2) < f < (n×340) / (w×3 / 2), and (n×340) / (h×5 / 2) < f < (n×340) / (h×3 / 2). This makes it possible to effectively suppress standing waves occurring in the vehicle interior.

[0073] The side wall member 40 may be light-transmitting, which can further increase the light transmittance of the entire sound absorbing structure 10 and further suppress adverse effects on the function and design of the light-transmitting plate 101a.

[0074] The sound absorbing structure 10 may be provided in the vehicle 100 so that the second surface member 30 is in contact with the light-transmitting plate 101a. This allows the sound absorbing structure 10 to face the interior of the vehicle cabin instead of the light-transmitting plate 101a, which has a high sound reflectivity, and therefore makes it possible to effectively reduce noise in the vehicle cabin.

[0075] The first surface member 20, the second surface member 30, and the side wall member 40 may partition a plurality of spaces, and the plurality of spaces may function as a plurality of resonators with different sound absorbing properties, thereby making it possible to absorb sound over a wider frequency range.

[0076] The acoustic system of this embodiment includes a sound absorbing structure 10 and a speaker that radiates sound that propagates into the interior space of a vehicle 100. This makes it possible to reduce distortion of the sound radiated from the speaker due to standing waves in the vehicle cabin (improving reproduction of the original sound) while minimizing restrictions on the speaker layout.

[0077] The vehicle 100 of this embodiment includes a vehicle body including a light-transmitting plate 101a having optical transparency, and a sound-absorbing structure 10 provided in the vehicle 100. This makes it possible to provide a vehicle interior with a good acoustic environment, thereby improving the riding experience of the passengers.

[0078] (4) Variations A modification of this embodiment will now be described.

[0079] In the above-described embodiment, the length of the resonators in the normal direction (i.e., direction D) of the surface of the first surface member 20 is uniform. However, this is not limiting, and the thickness of the sound absorbing structure 10 in direction D may be non-uniform. For example, the thickness of the sound absorbing structure 10 in direction D may be configured to be thicker in the center as viewed from the -D direction than in the peripheral portion as viewed from the -D direction. With this configuration, the volume of each resonator can be made larger than when the thickness of the sound absorbing structure 10 is aligned with the thickness of the peripheral portion as viewed from the -D direction, and as a result, the sound absorbing performance in the low frequency band can be improved.

[0080] At least one of the first surface member 20, the second surface member 30, and the side wall member 40 provided in the sound absorbing structure 10 may be configured to be movable. Also, a new member may be added inside the resonator. This makes it easy to adjust the shape and size of the resonator, and allows the sound absorbing characteristics of the sound absorbing structure 10 to be adjusted as desired.

[0081] In the above-described embodiment and each of the modified examples, the sound absorbing structure 10 is rectangular when viewed from the -D direction, an opening is provided on the surface of the sound absorbing structure 10 on the -D direction side, and the inside of the sound absorbing structure 10 is divided into a plurality of resonators (resonance spaces) by the side wall members 40. However, the shape of the sound absorbing structure 10 when viewed from the -D direction may be another polygon, circle, or ellipse. Also, the opening may be provided on a surface of the sound absorbing structure 10 other than the surface on the -D direction side. Also, the inside of the sound absorbing structure 10 may include a structure other than the resonance space.

[0082] In the sound absorbing structure 10 according to the present embodiment described above, a resonator (resonance space) is formed by the first surface member 20, the second surface member 30, and the sidewall member 40. The first surface member 20 provided in the sound absorbing structure 10 may be configured to be detachable from the sidewall member 40. This makes it possible to easily replace the first surface member 20 and improve the sound absorbing characteristics of the sound absorbing structure 10 even if the first surface member 20 is worn out and the sound absorbing characteristics of the sound absorbing structure 10 deteriorate. In addition, by replacing the first surface member 20 with another first surface member 20 having a different hole parameter, the sound absorbing characteristics of the sound absorbing structure 10 can be adjusted as desired. In addition, when the first surface member 20 and the side wall member 40 are separable, the partition dividing the internal space of the sound absorbing structure 10 may be provided in the first surface member 20 (i.e., the side wall member 40 may constitute only the outer shell of the sound absorbing structure 10 and may not include a member that partitions the internal space), or it may be provided in the side wall member 40, or it may be a member independent of both the first surface member 20 and the side wall member 40.

[0083] In the description of the present embodiment, an example has been described in which the sound absorbing structure 10 is configured by connecting six sound absorbing units in the W direction, each of which is made up of a resonator 11, a resonator 12, a resonator 13, and a resonator 14 connected along the +H direction to the -H direction. However, the multiple resonators constituting the sound absorbing unit may be connected in a direction non-parallel to the H axis (for example, the W direction or a diagonal direction with respect to the H axis). The multiple resonators constituting the sound absorbing unit may be three or less, or five or more. Similarly, the sound absorbing units may be connected in a direction non-parallel to the W axis (for example, the H direction or a diagonal direction with respect to the W axis). The multiple sound absorbing units may be connected in five or less, or seven or more. Furthermore, the multiple resonators constituting the sound absorbing structure 10 may all have different sound absorbing characteristics. By arranging multiple resonators with different sound absorbing characteristics side by side, it is possible to obtain a sound absorbing effect in a wider frequency band than when the same resonators are arranged side by side. On the other hand, when the same resonators are arranged side by side, a higher sound absorbing effect can be obtained in a specific frequency band than when a plurality of resonators with different sound absorbing characteristics are arranged side by side. Even if the shape of the resonators is the same, the sound absorbing characteristics of the resonators can be made different by making the hole parameters of the corresponding opening regions different. In any case, the sound absorbing structure 10 only needs to have a resonance space surrounded by an outer shell and perforations that communicate the inside and outside of the resonance space. That is, the sound absorbing structure 10 only needs to have at least one space in which air resonates, and it is not essential that the sound absorbing structure 10 has a partition wall that divides the internal space. Also, the number of perforations corresponding to each resonator of the sound absorbing structure 10 needs to be one or more. However, by forming a plurality of perforations for one resonator, it is possible to reduce the bias of the sound absorption coefficient according to the frequency (i.e., to make the peak of the sound absorbing characteristic gentler).

[0084] In the above description, an example has been shown in which the first surface member 20, the second surface member 30, and the side wall member 40 all have optical transparency. However, for example, the side wall member 40 may be configured to be visually recognized as a thin line when viewed from the -D direction. In such a case, even if the side wall member 40 is configured from a material that does not have optical transparency, adverse effects on the function and design of the light-transmitting plate 101a may be minor. Therefore, a part or all of the side wall member 40 may be configured from a material that does not have optical transparency.

[0085] In the above description, an example has been shown in which the sound absorbing structure 10 is installed so as to cover the light-transmitting plate 101a. For example, the sound absorbing structure 10 is provided on the vehicle 100 so that the second surface member 30 is in contact with the light-transmitting plate 101a. However, it is also possible to configure the light-transmitting plate 101a as a part of the sound absorbing structure 10. For example, the second surface member 30 may configure the light-transmitting plate 101a. This can reduce the pressure on the vehicle interior space caused by the installation of the sound absorbing structure 10, compared to the case in which the sound absorbing structure 10 is attached to the light-transmitting plate 101a.

[0086] Although the embodiment of the present invention has been described in detail above, the scope of the present invention is not limited to the above embodiment. Furthermore, the above embodiment can be improved or modified in various ways without departing from the spirit of the present invention. Furthermore, the above embodiment and the modified examples can be combined. [Explanation of symbols]

[0087] 10: Sound absorbing structure 11:Resonator 12:Resonator 13:Resonator 14:Resonator 20: First side member 30: Second surface member 40: Side wall member 100: Vehicle 101: Body

Claims

1. A sound absorbing structure provided in a vehicle having a light-transmitting plate having optical transparency, a first surface member that is divided into an opening region corresponding to the opening and a non-opening region not corresponding to the opening and has optical transparency; a second surface member that faces the first surface member across a gap and has optical transparency; a sidewall member interposed between the first surface member and the second surface member; Equipped with a space defined by the first surface member, the second surface member, and the sidewall member functions as a resonator, the resonator is defined by a portion of the first surface member corresponding to the opening region and a portion of the first surface member corresponding to the non-opening region, the opening region is not located at a center of the non-opening region, The sound absorbing structure is provided on the vehicle such that the first surface member faces an interior space of the vehicle and at least a portion of the light passing through the light-transmitting plate passes through the first surface member. Sound absorbing structure.

2. The light-transmitting plate is a transparent or translucent member that separates the interior space of the vehicle from the exterior of the vehicle. The sound absorbing structure according to claim 1 .

3. Each of the opening regions has a plurality of perforations densely formed therein. The sound absorbing structure according to claim 1 .

4. Let f be the frequency at which the sound absorption coefficient of the sound absorbing structure is maximized, let l, w, and h be the interior length, interior width, and interior height of the vehicle, respectively, and let n be an integer of 1 or more. The frequency f is (n×340) / (l×5 / 2) < f < (n×340) / (l×3 / 2), (n×340) / (w×5 / 2) < f < (n×340) / (w×3 / 2), and (n×340) / (h×5 / 2) < f < (n×340) / (h×3 / 2) At least one of the following is satisfied: The sound absorbing structure according to claim 1 .

5. The sound absorbing structure according to claim 1 , wherein the side wall member is light-transmitting.

6. The sound absorbing structure according to claim 1 , wherein the sound absorbing structure is provided on the vehicle such that the second surface member is in contact with the light-transmitting plate.

7. The sound absorbing structure according to claim 1 , wherein the second surface member constitutes the light-transmitting plate.

8. the first surface member, the second surface member, and the side wall member partition the spaces into a plurality of spaces, and the spaces function as a plurality of resonators having different sound absorption characteristics. The sound absorbing structure according to any one of claims 1 to 7.

9. A sound absorbing structure according to any one of claims 1 to 7, a speaker that radiates sound that propagates into an interior space of the vehicle; An audio system comprising:

10. A vehicle body including a light-transmitting plate having light transmittance; a sound absorbing structure provided on the vehicle body; A vehicle comprising: The sound absorbing structure is a first surface member that is divided into an opening region corresponding to the opening and a non-opening region not corresponding to the opening and has optical transparency; a second surface member that faces the first surface member across a gap and has optical transparency; a sidewall member interposed between the first surface member and the second surface member; Equipped with a space defined by the first surface member, the second surface member, and the sidewall member functions as a resonator, the resonator is defined by a portion of the first surface member corresponding to the opening region and a portion of the first surface member corresponding to the non-opening region, the opening region is not located at a center of the non-opening region, The sound absorbing structure is provided on the vehicle such that the first surface member faces an interior space of the vehicle and at least a portion of the light passing through the light-transmitting plate passes through the first surface member. vehicle.

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