Sound insulation, absorption and diffusion. Can they be part of the same process? I understand that insulation, absorption and diffusion in acoustics are  different concepts. Notwithstanding, would it be correct to assume they may be part of the same process when all are used to achieve 'sound proofing' and 'acoustic treatment' in a certain scenario?
To put it differently, is it correct to say that by treating the sound within a room (with proper absorption and diffusion techniques) we can limit (up to a certain extent) the pressure of certain sound waves that will exit the room? 
More specifically, I would think that by treating a room with high absorption coefficients, a certain amount of sound energy will be transformed into heat energy (for instance using mineral wool). Shouldn't this mean that less energy will 'get out' of the room? Also, shouldn't this mean that we could potentially plan a room's construction with both sound proofing and acoustic treatment at the same time, without them being completely separate activities at the design stage? 
 A: A more accepted term for sound treatment is acoustic treatment.  Acoustic treatment deals with the quality of sound, whereas sound proofing deals with the attenuation of sound.  A recording studio may need to be acoustically treated in order to increase the fidelity of the recording equipment.  It also may need to be sound-proofed in order to avoid disturbing neighbors or transmitting sound to neighboring studios.
Sound proofing is relatively straight-forward.  Sound transmission is by vibration.  Mass-loading surfaces increases the energy required to make them vibrate.  A room of mass-loaded surfaces will not transmit sound as readily as a room of easily vibrating surfaces.  If you want to sound-proof a room, you can cover the walls and doors with mass-loaded vinyl sheeting, or with sheets of lead.  Also, you can make sure there are no connecting vibrating members between inner and outer surfaces.  This is possible by placing an inner surface on one set of studs, and the outer surface on another set of studs.
Acoustic treatment is more difficult and involves the shape and size of spaces and surfaces.  It will vary depending on the type of sound and the preference of the listener.  There are online acoustic calculators, generally geared to proprietary products, but these may not be suitable for all installations and goals.
Acoustic treatment and sound proofing should be treated separately.  Wall coverings that absorb energy are used to attenuate echoes within a room, but if you try to sound proof by changing the shape of sound waves within a room, you risk decreasing the fidelity.  Many years ago I worked on a construction crew that built a sophisticated recording studio.  As I remember, sound proofing was confined to reducing vibrations through the outer shell of the studios.  The quality of sound within the studios was handled through a separate design process.  
