Architectural acoustics and room acoustics are frequently confused, yet the two are very different things.
Room acoustics deals with the acoustical properties of an enclosed space when the sound source comes from within this enclosed space.
Architectural acoustics deals with the transmission of sound between two rooms, or from the inside to the outside of a room (and vice-versa).
From a more technical perspective
When sound hits a surface such as a wall (labelled W1 in this diagram, standing for sound power), a portion is reflected (Wrefl) and a portion is absorbed by the wall (Wabs).
Combined, absorption (Wabs) and reflection (Wrefl) always add up to 100%.
Absorption (Wabs) is composed of the following:
- Dissipation (Wdis), sound power which is converted to energy/heat when striking a structural component;
- Transmission, sound power which is transmitted to neighbouring spaces, can be described as:
- direct transmission (W2); or
- transmission to other building components by way of flanking (W3), structure-borne sound.
Thus an open window is an excellent absorber (100%) yet it is not a sound insulator. If an enclosed space must exhibit both high sound absorption and high sound insulation (for example a musician’s practice room in a densely-built neighbourhood), a multiple-layered construction must be utilized.
|Fundamental difference||Sound transmission/reception between two (or more) different rooms||Sound transmission/reception within one room|
|Location of sound source||Outside the room||Inside the room|
|Demands on structural components||Good sound insulation||Correct amount of sound absorption|
|Unit of measurement for structural components||Decibel (highly dependent on frequency)||(Alpha-W) αw (highly dependent on frequency)|
|Key performance indicators||Degree of sound transmission and respective sound insulation measures in dB||Reverberation time (most important indicator)|