When sound energy hits a boundary, some of it is reflected, some is absorbed, and some is transmitted through the boundary. The percentage of sound reflection, absorption and transmission depends on the boundary material. In general, soft porous materials absorb sound better than hard materials. How would you rate the following materials in terms of sound absorption, from most to least absorptive?

• Concrete
  
• Gypsum board
  
• Carpet
  
• Fiberglass
  
  

Placing more soft materials in the room will reduce the amount of sound energy in the room, while more hard materials will keep the sound energy in the space for a longer period of time.

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