Perforated soundproof structure and method of manfacturing the same

Abstract

A perforated soundproof structure is formed by oppositely arranging an external plate 1 and an internal plate 2 having a number of through-holes 2 a . The board thickness, hole diameter and open area ratio of the internal plate 2 are set to satisfy design conditions to give rise to a viscous effect in the air passing through the through-holes 2 a , and the design conditions are set so that the frequency bandwidth to attain an absorption coefficient of 0.3 or more is 10% or more of the resonance frequency.

1 . A perforated soundproof structure formed by oppositely arranging an external plate and an internal plate having a number of through-holes;
 the internal plate having protruding parts formed so that their apexes are located on the external plate side; and   the apexes of the protruding parts being bonded to the external plate through a damping member for damping vibration.   
   
   
       2 . The perforated soundproof structure according to  claim 1 , wherein the damping member is formed of a sound absorbing member having the function of absorbing noise. 
   
   
       3 . The perforated soundproof structure according to  claim 2 , wherein the sound absorbing member is a porous body obtained by compressing a fibrous or rectangular metal or porous body made of a nonwoven fabric. 
   
   
       4 . The perforated soundproof structure according to  claim 1 , further comprising a sound absorbing member for an absorbing noise provided around the damping member. 
   
   
       5 . The perforated soundproof structure according to  claim 4 , wherein the sound absorbing member is a porous body obtained by compressing a fibrous or rectangular metal or a porous body made of nonwoven fabric. 
   
   
       6 . The perforate soundproof structure according to  claim 1 , further comprising a sound absorbing member provided entirely over the sound source side of the internal plate. 
   
   
       7 . The perforated soundproof structure according to  claim 6 , wherein the sound absorbing member is a porous body obtained by compressing a fibrous or rectangular metal or a porous body made of nonwoven fabric. 
   
   
       8 . The perforated soundproof structure according to  claim 6 , wherein the sound absorbing member consists of one or more perforated plates having a number of through-holes, which are arranged through air layer.