310 ILLINOIS STATE ACADEMY OF SCIENCE 



plied and withdrawn from rooms by individual pipes that 

 are small in diameter and extend without break from 

 the air supply chamber to the rooms. This results in 

 considerable friction between the walls of the pipes and 

 the air, with a resultant weakening of the sound waves. 

 Without some efficient control of the transference of 

 sound through the ventilation system, it is a waste of 

 effort to construct soundproof walls, double doors, and 

 other contrivances for insulation. 



Soundproof Partitions. — Partitions between rooms 

 should be as rigid and free from air passages as possible. 

 For effective soundproofing of a group of rooms, the 

 partitions, floors, and ceilings between adjacent rooms 

 should be made continuous and rigid. Any necessary 

 openings for pipes, ventilators, doors, and windows 

 should be placed in outside or corridor walls where a 

 leakage of sound will be less objectionable. 



Absorption of Sound. — The absorption of sound is an 

 essential feature for soundproofing. Reflecting sound 

 and scattering it still leaves it with energy. It must be 

 absorbed ; that is, converted into heat energy by friction, 

 before it is eliminated as sound. This means that car- 

 pets, furniture, draperies, etc., should be present, or if 

 greater absorption is desired, hairfelt or similar mater- 

 ials must be installed. 



Soundproofing a Building. — *When soundproofing a 

 building, all details should be considered with respect 

 to the likelihood of transmission of sound. Each room, 

 as far as possible, should be made an insulated unit by 

 means of air spaces or air-filled materials that separate 

 it from surrounding walls. Pipes and ventilators should 

 be so installed as to minimize the chance of transfer of 

 sound. Patent doors are now available that will close 

 the door space at top, sides and bottom. In case a 

 troublesome sound is generated in the room, it may be 

 minimized by installing absorbing material on the walls. 



The insulation of sound is a complex problem, and a 

 successful solution is obtained only when all the possibili- 

 ties of transfer of sound are anticipated and guarded 



♦ "Soundproofing a Building", Architectural Forum, November, 1921. 



