A double wall of fairly light construction will give good sound insulation provided the two walls are not closely coupled mechanically by nails or cross members; that is, provided the walls are kept isolated or separated from each other as much as practicable.

163. The Relation of the Volume Control Setting to Reverberation Effects.- It was stated in section 157 that the sound energy within a closed room is reflected back and forth between the walls until entirely dissipated. The length of time required to dissipate the sound energy produced by a loudspeaker depends upon the amount of sound energy produced, the size of the room, and the amount of sound absorbing material in the room. If there is very little sound absorbing material in the room, a small amount of sound energy will produce a high volume of sound. If the sound energy is quickly absorbed a large amount of sound energy is required to give the desired volume level. If the same volume control setting were used for a nearly empty house as is used for a full house, the volume level would probably be too great, and an undesirable amount of reverberation would be experienced. Therefore, it is a good plan, when operating to a partially filled house, to reduce the volume control setting to give just enough volume so that the sound will be intelligible at the last row of seats used by the audience. This is particularly important when the house is excessively reverberant and where un-upholstered seats are used.

 
 
 
 
  Copyright 1930 RCA Photophone, Inc. 8