Soundproof structure

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=Eh2/(ρmax/ρmin) [N] (1)
• (Δd/L−0.025)/(0.06) [N]≤X [N]≤10 [N] (2)