In the Southeast Asia region especially, acoustic properties of residential buildings are often neglected by designers, developers, contractors, and even home buyers. Noises from both internal and external environments affects occupants’ daily lives, causing nuisance which can strongly deteriorate one’s living quality as a long-term effect. In this article, we will investigate building/room acoustics, and the actions that can be undertaken to improve the acoustical environment inside a building.

Room acoustics

In general, the acoustics of rooms can be divided into two groups: low frequency and high frequency. Sound in rooms can be highly affected by the reflective properties of the surfaces in the room. This is because multiple reflections may occur if the room surfaces are highly reflective, which then leads to a reverberant field in addition to the direct field from the source especially at higher frequency range. Therefore, at any point in the room, the overall sound pressure level is influenced by the energy contained in both the direct and reverberant fields (Crocker, 2007).

Sound transmissions in buildings

Sound can be transmitted within a building by transmitting through air in the spaces bounded by walls or roofs/ceilings, known as airborne transmission. Another way would be through structural transmission through the structural assemblies of the building, or impacts.

Airborne sound originates from a source that radiates sound waves into the air, which would then impinge on the building surfaces. A good example of airborne sound will be speech, or music from a television or loudspeaker. On the other hand, impact sound is being generated when an object strikes the surface of a building. The commonly heard impact sounds that we can hear in buildings are footsteps, furniture-dragging sounds, cleaning, and other equipment that is used directly on the floor surfaces. To overcome these noises, good sound isolation should be considered for all the possible paths for sound and the junctions between walls and floors, not just at the direct path through common wall or floor.

Sound insulation – airborne and impact

It is imperative to consider the control of airborne and impact sound transmission through the building elements like walls, ceilings, or floors, as stated above. In this case, sound insulation methods will be crucial. Different methods can be implemented for airborne, impact and flanking sounds (Crocker, 2007).

For airborne sound, insulation can be applied at any building element. This is because when sound hits on a surface, a very small fraction of the incident energy will be radiated from the other side. The sound transmission loss (TL), which is the ratio of the incident sound energy relative to the transmitted sound energy is typically measured. TL can be expressed in decibels (dB), and it is sometimes known as sound reduction index (R) in European and ISO standards. The elements to be used in buildings for sound insulation are measured in accordance with standards, where the commonly seen method would be the two-room method. A test specimen would be mounted between a reverberant source room, and a receiver room such that the only significant path for sound to transmit through is the specimen, and other possible transmission paths would be suppressed. As such, it will be useful to determine the TL of the building elements/materials so that one can estimate the airborne sound insulation performance inside the building space.

As for impact sound which typically radiates from a floor into rooms below or horizontally, insulation can be done via floor coverings or floor slabs. This is because the applications of these items can reduce the impact sound pressure levels that travels into the receiver room. The typical methods of insulation are adding soft floor coverings on concrete slab, increasing the thickness of concrete floors, or implementing floating floors.

Single number ratings

To know the acoustic information of an insulation element, the standard method would be to refer to the single number ratings of that element. These ratings would be assigned to building materials based on their sound transmission spectra by the means of reference curves or weighted summation procedures.

The most used single-number rating for airborne sound insulation is the Sound Transmission Class (STC), which is in accordance with the American Society for Testing and Materials (ASTM) E413. There is another equivalent number called the Weighted Sound Reduction Index (R_w), which is based on the International Organization for Standardization (ISO) standard ISO 717.