JP7689603B2 - Sound absorbers and sound absorbing structures - Google Patents

Description

The present invention relates to a sound absorber and a sound absorbing structure. More specifically, the present invention relates to a sound absorber and a sound absorbing structure using the same, which includes a sound absorber body that is installed inside at least one of the ceiling, wall or floor surfaces facing a space and a structure installed in the space (hereinafter referred to as the "ceiling surface, etc.") or exposed inside the space, and the sound absorber body has an internal slit and a cavity that communicates with the internal slit, and the internal slit is connected to the space to absorb sound within the space.

As an example of a sound absorber and sound absorbing structure as described above, the one described in the following Patent Document 1 is known. This sound absorber is a Helmholtz resonator that resonates through the opening 102 and absorbs sound. The resonator described in this document has different resonance frequencies depending on the volume of the cavities 4 and 5 and the width of the opening 102, etc., and therefore different sound absorption frequency bands.

However, when a sound absorber is attached to a ceiling as shown in Figures 5 and 6 of the document, and a ceiling board 46 is further attached around the opening 102, a neck portion is formed around the opening 102 depending on the thickness of the ceiling board, and the height of this neck portion and the width of the slit facing the opening 102 affect the height of the neck portion and the width of the slit. In that case, the resonant frequency of the resonator differs from the original design, and there is a problem that the desired sound absorption performance cannot be achieved. There is also a demand for a sound absorber whose resonant frequency can be adjusted appropriately according to the environment.

JP 2018-188954 A

In view of the current situation, the present invention aims to provide a sound absorber and sound absorbing structure that is not affected by changes in resonance frequency due to the dimensions of the finishing material of the ceiling surface, etc., even when stored inside the ceiling surface, and that allows the resonance frequency to be adjusted even when installed outside the ceiling surface, etc.

In order to achieve the above object, the sound absorber according to the present invention is characterized in that it comprises a sound absorber body that is installed inside at least one of the ceiling, wall or floor surfaces facing a space and the structure installed in the space (hereinafter referred to as the "ceiling surface, etc.") or exposed inside the space, the sound absorber body has an inner slit and a cavity that communicates with the inner slit, and is configured to absorb sound within the space by connecting the inner slit to the space, and further comprises a neck member that forms a neck outside and/or inside the inner slit by attaching it near the inner slit, the neck member is made up of a first neck and a second neck of different lengths joined at a 90 degree angle, one of the first and second necks is attached near the inner slit as a fixed part and the other is used as a neck, and the neck height and neck slit width can be changed by selecting the use of either the first or second neck as a neck and the attachment position.

In addition, an inner neck portion may be provided that extends from the inner slit into the hollow portion.

In the above configuration, a sealing material is provided to cover the path from the inner slit of the neck member to the inside of the sound absorber body, and the sealing material prevents the inside of the inner slit from being seen without impairing the sound absorption properties, and the neck member may have a neck portion and a fixing portion that is bent at approximately 90 degrees, and a step portion that receives the sealing material may be formed between the neck portion and the fixing portion. This configuration can prevent foreign objects from being inserted into the inner slit from the outside, and can also improve the design as seen from the outside. Since the sealing material is received at the step portion, it is easy to replace the sealing material even if it is damaged.

In addition, a flow resistance material that absorbs sound may be provided inside the cavity near the inner slit and oriented toward the back of the inner slit, and the width of the inner slit may be made wider than the neck slit width. With this configuration, the neck portion of the neck member can be expanded to the width of the inner slit, making it easier to adjust the width of the resonance frequency adjustment. Moreover, since the inner slit portion can be made wide, there is an advantage that flow resistance material such as a sound absorbing material can be easily inserted using the inner slit.

The flow resistance material may be provided on both sides of the inner slit, and a cavity may be located behind each of the flow resistance materials. The sound absorbers can be stored and positioned rationally by effectively utilizing the space above the ceiling, behind the walls, etc. Also, the flow resistance material may be provided on only one side of the inner slit, and a cavity may be located only behind the flow resistance material. This configuration makes it easier to install even in environments where there is no storage space on one side of the ceiling or behind the wall due to a slab.

A spacer may also be provided that can be inserted between the neck member and the sound absorber body to change the neck height and/or the neck slit width. With this configuration, the spacer can be used to accurately adjust the resonant frequency.

On the other hand, a sound absorbing structure using a sound absorber according to any of the above configurations is characterized in that the sound absorber body is stored inside a ceiling surface or the like, and the neck protrudes from a slit formed in the surface finishing material. According to this configuration, the neck can be installed independently regardless of the thickness of the surface finishing material, so that a sound absorbing structure can be constructed with a desired resonance frequency. Therefore, it is now possible to freely set and design the spacing of the slits in the surface finishing material independently of the neck.

The features of the sound absorber and sound absorbing structure of the present invention described above mean that even when the sound absorber and sound absorbing structure are stored inside a ceiling surface, they are not affected by the dimensions of the finishing material of the ceiling surface, etc., and the resonant frequency can be adjusted even when the sound absorber and sound absorbing structure are installed outside a ceiling surface, etc.

Other objects, configurations and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments of the invention.

1A is a vertical cross-sectional view of a sound absorbing structure in which a sound absorber according to the present invention is stored in a ceiling corner, and FIG. 1B is an enlarged cross-sectional view of the sound absorber. 4 is a graph showing the sound absorption characteristics of a sound absorber according to the present invention, in which the neck height l and the neck slit width b are changed. 1 is a graph showing the sound absorption characteristics of a sound absorber according to the present invention, in which the neck slit width is 15 mm and the neck height 1 is changed. 1 is a graph showing the sound absorption characteristics of a sound absorber according to the present invention, in which the neck slit width b is changed and compared with other sound absorption techniques. 1 is a cross-sectional view of a sound absorbing structure in which a sound absorber according to the present invention is housed in the center of a wall surface. 1 is a cross-sectional view of a sound absorbing structure in which a sound absorber according to the present invention is stored in a corner of a wall surface. 1 is a vertical cross-sectional view of a sound absorbing structure in which a sound absorber according to the present invention is stored in a lower corner of a wall surface. FIG. 2A is a perspective view showing the installation location of a sound absorber according to the present invention with a neck slit, and FIG. 2B is a schematic perspective view showing the relationship between the volume of the sound absorber body and the dimensions of the neck portion. FIG. 11 is a longitudinal cross-sectional view showing various mounting configurations between a sound absorber and a neck member according to the present invention, in which (a) is when a first neck is used, (b) is when a second neck is used, (c) is when the first neck is used with a width spacer, and (d) is when the first neck is used and also with a depth spacer. FIG. 11 is a longitudinal cross-sectional view of an embodiment of a sound absorber according to the present invention in which a step is provided in the neck member, (a) being a basic form in which a step is provided, (b) being a form in which three neck portions are provided, in which a first neck is used, and (c) being a form in which a second neck is used. FIG. 1(b) is a cross-sectional view showing a modified example of the sound absorber shown in FIG. 1(b), where (a) is a case where the inner surfaces of the inner neck portion 25 and the neck portion 31 are flush with each other, and (b) is a case where the slit of the neck portion 31 is narrower than that in (a). 1(b), in which (a) is a cross-sectional view showing a modified example of the sound absorber shown in FIG. 1(b), in which (a) is provided with only an inner neck portion 39, and (b) is a cross-sectional view showing a modified example of the sound absorber shown in FIG. 1(b), in which (a) is provided with both an inner neck portion 39 and a neck portion 31. 1(b), in which (a) is a cross-sectional view showing a modified example of a protrusion for fixing a sound-absorbing material, and (b) is an example in which a neck portion 31 having a different shape is provided. FIG. 10A and 10B are longitudinal cross-sectional views showing different forms when the sound absorber body is made from multiple parts, in which (a) is an example where the sound absorber body is divided into seven parts, (b) is an example where the sound absorber body is divided into seven different parts, and (c) is an example where the sound absorber body is divided into three parts.

Next, the present invention will be described in more detail with reference to Figures 1 to 6 of the attached drawings as appropriate.

The sound absorber 2 according to the present invention shown in FIG. 1 is installed in, for example, the indoor structure 100 shown in FIG. 1 and 6(a) to form a sound absorbing structure 1. In the indoor structure 100 in FIG. 6(a), a ceiling board 107, an interior wall board 113, a floor slab 120, and a support 130 are shown. The symbols I, III, IV, and V shown in the figure indicate the positions of the neck slits 32 corresponding to the mounting forms in FIG. 1, 3, 4, and 5, respectively. Each sound absorber is stored in the internal space of the surface finishing material such as the ceiling board 107 and the interior wall board 113, and a neck to be described later protrudes from the slit of the surface finishing material. Alternatively, the sound absorber may be stored in the internal space shown in symbols XI, XII (when a floor board is provided at a distance from the floor slab instead of the floor slab 120), and XIII. Additionally, the sound absorber may be installed alone on the outside of the surface finishing material at the position indicated by reference symbol XIII, and similarly, the sound absorber may be installed alone outside the surface finishing material at the positions indicated by reference symbols I, III, IV, V, XI, and XII.

As shown in FIG. 1, the sound absorber 2 is made up of a sound absorber body 20 and a neck member 30, both of which are long in the direction perpendicular to the page, with a sealant 6 provided between these two members. Note that the sound absorbing performance is not affected even if the sealant 6 is not provided. The sound absorber body 20 has a hollow portion 3 inside, and contains a pair of sound absorbing materials 5, 5 that act as flow resistance materials.

The sound absorber body 20 is symmetrical with respect to the central inner slit 23, with the opening side plate 21 having opening side protrusions 21a, 21a on the left and right, and the rear side plate 22 having rear side inner protrusions 22b, 22b and rear side outer protrusions 22a, 22a on the left and right, and each protrusion holds a pair of left and right sound absorbing materials 5, 5. The sound absorber body 20A is configured with a cavity located at the rear of each of the sound absorbing materials 5, 5.

In this embodiment, the neck member 30 has an L-shaped angle, and the neck portion 31 and the fixing portion 33 are joined at an angle of 90 degrees. The neck slit 32 is formed between the neck portions 31, 31 of the pair of neck members 30, 30 fixed to the opening side plate portion 21 by the fixing portion 33. A sealing material 6 is interposed between the opening side plate portion 21 and the fixing portion 33, and all of these are attached with, for example, an adhesive. Both the opening side plate portion 21 and the fixing portion 33 may be fixed by driving screws into them. The sealing material 6 is made of, for example, a metal mesh, a glass fiber cloth, a nonwoven fabric, etc., and is made of a material that covers the inner slit 23 and prevents the inside of the inner slit 23 from being seen without impairing the sound absorption properties. In addition, if it is okay to see the internal structure, the sealing material 6 does not need to be attached.

The inner slit 23 is cut out wider than the distance between the inner protrusions 22b, 22b on the far side, making it easier to insert and install the sound absorbing material 5. The neck slit width b of the neck slit 32 can be adjusted by widening it to the maximum width of the inner slit 23. The neck portion 31 and the fixing portion 33 have different lengths, and if they are inverted to become the first neck 30a and the second neck 30b, respectively, the neck height l can be adjusted.

The sound absorber 2 is made up of the sound absorber body 20, the sealing material 6, and the neck member 30, all of which are long in the direction perpendicular to the paper. In the example of FIG. 6(a), the slits are set to be formed over almost the entire width of the ceiling, and the neck slit length is indicated by the symbol a. The length can be stopped midway. However, the end of the neck portion must be blocked by another member, as shown by the symbol 31e in FIG. 6(b), just like the neck member 30. That is, both ends of the entire length need only be blocked at the very least with a plate material that follows the outline of the sound absorber body 20 and the neck member 30 in FIG. 1, but a short member like the neck member 30 may be provided perpendicular to the neck member 30, and both ends of the sound absorber body 20 may also be blocked with another plate material. Of course, the neck slit length a is not limited to the entire width of the room, and may be stopped midway.

To further explain the indoor structure 100 in which the sound absorber 2 is installed, a siding support 103 extending in a direction perpendicular to the paper surface is supported by a hanging bolt 101 supported by a ceiling slab via a hanger 102, and a siding 104 is attached perpendicularly, and a ceiling board 107 is attached to the siding 104. Between the mounting channel 106 attached to the foundation wall board 112 and the siding support 103, mounting angles 105 are intermittently provided in a direction perpendicular to the paper surface, and the sound absorber body 20 is attached below it. A runner 110 is provided at the bottom of the mounting channel 106, extending in a direction perpendicular to the paper surface, and studs 111 are erected intermittently in a direction perpendicular to the paper surface below it, and the interior wall board 113 is supported by these studs 111. In this example, since there is space behind both the interior wall board 113 and the ceiling board 107, a double-sided sound absorbing sound absorber body 20A is used.

FIG. 2 shows an example of the effect of the change in the resonance frequency of the sound absorber with the above-mentioned configuration. The horizontal axis indicates the 1/3 octave band center frequency (Hz), and the vertical axis indicates the sound absorption coefficient by the reverberation room method. The neck height l and the neck slit width b were changed. In FIG. 2a, the circle marks indicate l: 10 mm, b: 10 mm, and the triangle marks indicate l: 20 mm, b: 10 mm. By increasing the neck height l, the resonance frequency f ₀ can be shifted to the low-frequency side, increasing the sound absorption coefficient in the low-frequency range, and increasing the sound absorption coefficient at the resonance frequency f _0. The square marks indicate l: 35 mm, b: 15 mm, and it can be seen that the increase in the neck slit width b, combined with the increase in the neck height l, further shifts the resonance frequency f ₀ and the center of gravity of the graph integral value to the low-frequency side.

In FIG. 2b, the circles indicate l: 20 mm, b: 15 mm, and the triangles indicate l: 35 mm, b: 15 mm. It can be seen that by increasing the neck height l, the center of gravity of the graph integral value and the resonance frequency f ₀ shift to the lower range.

In Fig. 2c, the circle marks indicate l: 20 mm, b: 20 mm, and the triangle marks indicate l: 20 mm, b: 10 mm, and for example, by reducing the neck slit width b, the resonance frequency _f0 can be adjusted to the lower range. The rock wool sound absorbing boards indicated by the square marks and the carpet tiles indicated by the diamond marks can supplement the insufficient parts and selectively absorb the main frequency bands at conversation levels.

Figure 3 shows an example in which a slit is formed in the interior wall board 113 at position III in Figure 6 (a) to house the sound absorber 2. The studs 111 extend in the direction perpendicular to the paper surface, and the double-sided sound absorber body 20A is similarly arranged along the studs 111, so sound-absorbing slits can be formed in the wall surface along the top and bottom of the space.

Figure 4 shows an example in which a sound absorber 2 is housed in a slit formed in the corner where the interior wall boards 113, 113 intersect at right angles at position IV in Figure 6 (a). In this example, a one-sided sound absorbing sound absorber body 20B is used, and it can be installed particularly well when, for example, there is no stud 111 on the left side and the interior wall board 113 is close to the wall slab 114. Therefore, if there is space on the left side, a two-sided sound absorbing sound absorber body 20A with the part indicated by the symbol 20C may be used.

The same L-angle neck member 30 as in the previous embodiment is used on the right side of the inner slit 23, but a flat neck member 35 is used on the left side of the inner slit. Since the left-side inner wall board 113 can form part of the neck, the flat neck member 35 may be used for design purposes in addition to homogenizing the material of the neck. In this example, the left end of the sealing material 6 is bent and attached to the outer wall of the sound absorber body 20.

Figure 5 shows an example in which a sound absorber 2 is stored in a slit formed in the corner where the lower end of the interior wall board 113 and the floor slab 120 intersect at right angles at position V in Figure 6 (a). In this example, a one-sided sound absorber body 20B is used as in the previous example, and the side where the inner slit 23 is formed is in contact with the floor slab 120, so that the floor slab 120 is used as part of the neck.

A lower runner 121 is placed on top of the sound absorber body 20, extending along the sound absorber body 20 in a direction perpendicular to the plane of the paper, and a stud 111 is provided on top of the lower runner 121, to which an interior wall board 113 is fixed.

7 shows a modified example of the neck member 30. In FIG. 7(a), the neck portion 31 and the fixed portion 33 are provided with turn-back portions 34 at 90 degrees each other, and the lengths of the neck portion 31 and the turn-back portions 34 are different to form the first and second neck portions 30a and 30b. By using the second neck portion 30b as shown in FIG. 7(b), it is possible to adjust the neck height l from l1 to l2 lower with more reliable dimensional accuracy than when the first neck portion 30a is used. As shown in FIG. 7(c), the neck width b can be expanded by a thickness of 2ΔW by inserting a width spacer 36 between each turn-back portion 34 (or the portion indicated by the symbol 31 when inverted) and the side of the sound absorber main body 20. Furthermore, by inserting a depth spacer 37 between the fixed portion 33 and the bottom surface of the sound absorber main body 20 as shown in FIG. 7(d), the neck height l can be expanded by a thickness Δt of the depth spacer 37.

Figure 8 shows a modified example for making the sealing material 6 replaceable, in which a step 38 is provided between the neck portion 31 and the fixed portion 33, and the sealing material 6 is stored in this step 38 and attached to the sound absorber body 20. With this configuration, the sealing material 6 is not sandwiched between the fixed portion 33 and the sound absorber body 20, so it is easy to replace it via the neck slit 32. Figures (b) and (c) show a configuration in which the step 38 is provided with the aforementioned folded portion 34, and by using the first and second neck portions 30a and 30b in reverse as in the previous embodiment, the neck height l can be changed to l1 and l2.

Figure 9 shows a modified example of the sound absorber shown in Figure 1 (b), where (a) shows a case where the inner surfaces of the inner neck portion 25 and the neck portion 31 are flush with each other. The inner neck portion 25 enters the inside at a position corresponding to the rear inner protrusion 22b, and together with the neck portion 31 of the neck member 30, the neck height becomes l. A portion of the sound absorbing material 5 is fixed by the inner neck portion 25. The volume V in the previous equation 3 is calculated as the following equation 4, since the volume of the inner neck portion 25 is excluded.

Formula 4
V=A*B*L-a*b2*l2
V: cavity volume, A: cavity length, B: cavity width, L: cavity height, a: neck slit length, b: neck slit width, l: neck height, b2: inner neck outer width, l2: inner neck height

In this example, the inner neck portion 25 is fixed and cannot be adjusted, but if the sound absorber body 20 is divided as shown in Figures 12(b) and (c) below, the spacing of the inner neck portion 25 can be adjusted. In this example, the neck member 30 is provided separately, so the neck slit width b and neck height l can be changed.

In Figure 9(b), in addition to the inner neck portion 25, an inner protrusion 21b is provided on the opening side to hold the sound absorbing material 5. The slit in the neck portion 31 is narrower than that in Figure 9(a), and the narrowest part is the neck slit width b.

In Figure 10, the inner neck portion 39 is a separate member from the sound absorber body 20, and in Figure 10(a), it can be inverted to the first neck 39a and the second neck 39b, and the neck slit width b can also be adjusted.

Figure 10(b) shows the case where both the inner neck portion 39 and the neck portion 31 are provided. In addition to the inner neck portion 39, an inner protrusion 21b is provided on the opening side to hold the sound absorbing material 5. When providing the sealing material 7, in addition to a sealing sheet 7a similar to the sealing material 6 described above, sound absorbing materials 7b and 7c made of the same material as the sound absorbing material 5 described above may be provided in the neck slits 32.

Figure 11 (a) shows a modified example of the protrusions for fixing the sound-absorbing material, in which a pair of opening side central protrusions 21c and a pair of rear side central protrusions 21c face each other on the opening side plate portion 21 and the rear side plate portion 22, respectively, and each protrusion 21c, 22c bites into the center of the width of the sound-absorbing material 5 to fix it in place.

Figure 11 (b) shows an example in which a neck portion 31 of a different shape is provided, and this neck portion has a step portion 31c between a thin neck portion 31a and a thick neck portion 31b. The thin neck portion 31a has a neck slit width b.

In the above embodiment, the sound absorber body 20 is integrally formed by extrusion molding or the like in the direction perpendicular to the page, but it may be constructed by combining multiple parts as shown in Figure 12. In Figure 12(a), the sound absorber body is divided into seven parts, with one channel part 20a combined with two angle parts 20b to create the main part, and a small channel 20c and a small angle 20d combined inside to form the protrusions of the sound absorbing material 5.

In Fig. 2(b), the sound absorber body is divided into seven different parts, with two large channel sections 20f and two small channel sections 20g connected by a flat plate 20h. At the front, the large channel section 20f and the small channel section 20g are each connected by a neck member 30. Fig. 2(c) shows an example in which the sound absorber body is divided into three parts. Two large channel sections 20f with protrusions 21ab and 22ab are connected by a flat plate 20h.

The present invention can be modified in various ways without departing from the spirit of the invention, and the above embodiments can be implemented in combination, for example, by combining the examples in Figures 9 and 10 with those in Figure 12.

The present invention can be used as a sound absorber and sound absorbing structure that can be installed as an existing or additional installation on at least one of the ceiling, wall or floor surfaces facing a space, and on structures to be installed within the space (wood boards, metal, glass, stone, tiles, etc.). It can also be installed exposed on the outside of the surface finishing material within the space to adjust the acoustic environment by absorbing sound. It can absorb sound in the frequency range where the sound absorbing power of conventionally used finishing sound absorbing materials (glass wool, rock wool sound absorbing boards, etc.) is insufficient, and in the main frequency range of human conversation level, and can be used as a base material for various materials.

1: Sound absorbing structure, 2: Sound absorber, 3: Hollow portion, 5: Sound absorbing material, 6: Sealing material, 7a: Sealing sheet, 7b, 7c: Sound absorbing material, 7: Sealing material, 20: Sound absorber body, 20A: Double-sided sound absorbing sound absorber body, 20B: Single-sided sound absorbing sound absorber body, 21: Opening side plate portion, 21a: Opening side protrusion, 21b: Opening side inner protrusion, 21c: Opening side central protrusion, 22: Side plate portion, 22a: Rear outer protrusion, 22b: Rear inner protrusion, 21c: Rear central protrusion, 23: Inner slit, 25: Inner neck portion, 30: Neck member, 30a: First neck, 30b: Second neck, 31: Neck portion, 31a: Thin neck portion, 31b: Thick neck portion, 31c: Step portion, 32: Neck slit, 33 : Fixed part, 34: Folded part, 35: Flat neck member, 36: Width spacer, 37: Depth spacer, 38: Step, 39: Inner neck, 39a: First neck, 39b: Second neck, 100: Indoor structure, 101: Suspension bolt, 102: Hanger, 103: Rough sill support, 104: Rough sill, 105: Mounting angle, 106: Mounting channel, 107: Ceiling board, 110: Runner, 111: Stud, 112: Foundation wall board, 113: Inner wall board, 114: Wall slab, 120: Floor slab, 121: Lower runner, 130: Support, B: Cavity width, a: Neck slit length, b: Neck slit width, L: Cavity height, l: Neck height

Claims (8)

A sound absorber comprising: a sound absorber body that is installed in at least one of a ceiling surface, a wall surface, or a floor surface facing a space, and a structure installed in the space (hereinafter referred to as a "ceiling surface, etc."), or that is exposed in the space, the sound absorber body having an inner slit and a cavity that communicates with the inner slit, and the inner slit communicates with the space to absorb sound in the space,
The sound absorber further includes a neck member that forms a neck outside the inner slit by being attached near the inner slit, the neck member comprising a first neck and a second neck of different lengths joined at a 90 degree angle, one of the first and second necks being attached near the inner slit as a fixed part and the other being used as the neck, and the neck height and neck slit width being changeable depending on the selection of whether the first or second neck is used as a neck and the attachment position. The sound absorber of claim 1 further comprising an inner neck portion that extends from the inner slit into the cavity. A sound absorber according to claim 1, in which a sealing material is provided to cover the path from the inner slit of the neck member to the inside of the sound absorber body, the sealing material prevents the inside of the inner slit from being seen without impairing the sound absorbing properties, the neck member has a neck portion and a fixing portion that is bent at approximately 90 degrees, and a step portion is formed between the neck portion and the fixing portion to receive the sealing material. A sound absorber according to any one of claims 1 to 3, in which a flow resistance material that absorbs sound is provided inside the cavity near the inner slit and oriented toward the back of the inner slit, and the width of the inner slit is formed wider than the width of the neck slit. The sound absorber of claim 4, in which the flow resistance material is provided on both sides of the inner slit, and a cavity is located deep inside each of the flow resistance materials. The sound absorber of claim 4, in which the flow resistance material is provided on only one side of the inner slit, and the cavity is located only behind the flow resistance material. A sound absorber according to any one of claims 1 to 6, which is provided with a spacer that can be inserted between the neck member and the sound absorber body to change the neck height and/or the neck slit width. A sound absorbing structure using the sound absorber according to any one of claims 1 to 6, in which the sound absorber body is stored inside a ceiling surface or the like, and the neck protrudes from a slit formed in a surface finishing material.

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