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
Copyright 1930 RCA Photophone, Inc.