Soundproof structure

1. A soundproof structure comprising:

at least one soundproof cell which comprises a frame having a hole portion and a film fixed to the frame so as to cover the hole portion and in which a rear space of the film is closed,

wherein the film has a surface density distribution including at least one high surface density region and a low surface density region,

the at least one high surface density region comprises a plurality of high surface density regions which are disposed on an entire surface of the film, and

assuming that a shortest line segment length among line segments connecting end portions of the high surface density regions adjacent to each other and line segments connecting the high surface density regions and end portions of the hole portions of the frame to each other is Δd [m], a longest line segment length among line segments connecting the end portions of the hole portions of the frame to each other is L [m], a Young's modulus of a material of the low surface density region is E [Gpa], an average film thickness of the low surface density region is h [m], a maximum surface density of the film is ρmax, and a minimum surface density of the film is ρmin, a parameter X of the film defined by the following Equation (1) satisfies the following Inequality (2)

X=Eh 2 /(ρmax/ρmin)[N]  (1)

(Δ d/L− 0.025)/(0.06)[N]≤ X [N]≤10[N]  (2).

2. The soundproof structure according to claim 1 ,

wherein a ratio ρmax/ρmin between the maximum surface density ρmax of the film and the minimum surface density ρmin of the film is 1.5 or more.

3. The soundproof structure according to claim 1 ,

wherein the film is formed of two or more kinds of materials.

4. The soundproof structure according to claim 1 ,

wherein the film has a protruding portion or a weight forming the at least one high surface density region.

5. The soundproof structure according to claim 4 ,

wherein the film having the protruding portion is a resin film having unevenness.

6. The soundproof structure according to claim 1 ,

wherein the film and the frame are integrally formed.

7. The soundproof structure according to claim 1 ,

wherein the soundproof cell is smaller than a wavelength of a first natural vibration frequency of the film.

8. The soundproof structure according to claim 7 ,

wherein the first natural vibration frequency is 100000 Hz or less.

9. The soundproof structure according to claim 1 ,

wherein the soundproof structure has a structure in which one or more soundproof cells are disposed in an opening member having an opening.

10. The soundproof structure according to claim 9 ,

wherein the soundproof cell is disposed in the opening member in a state in which a film surface of the film is inclined with respect to an opening cross section of the opening member and a region serving as a ventilation hole through which gas passes is provided in the opening member.

11. A method of manufacturing the soundproof structure according to claim 4 , the method comprising:

manufacturing the film having the protruding portion by forming unevenness on the film by resin molding or imprinting.

12. A method of manufacturing the soundproof structure according to claim 1 , the method comprising:

forming the film and the frame together with a 3D printer.