1.2 Sound transfer in buildings

There are two basic mechanisms where by sound can transfer. Noise can pass from one room to another either through the surrounding air (airborne noise) or the building structure itself (structure-borne noise).

1.      Airborne noiseor sound that is transmitted via the air e.g. voices, TV, Radio, music instruments, DVDs, home theatre.

2.      Structure borne noise: where a structure is directly vibrated and the vibration is transmitted through the structure in all directions where this energy vibrates a surface in a space. The surface radiates the vibration as audible noise in the same way that a loudspeaker cone converts movement of the cone to audible sound. Examples: railway vibration, plant vibration, demolition activities, impact noise, including foot fall on tiles and timber floors, movement of furniture, dropping of cutlery, hydraulics/pipe noise

A third mechanism is a combination of the above two

3.      Airborne through structure:Sound generated in one room reaches the wall or floor, vibrates that surface and then is reradiated by the surface on the other side of the wall or floor to the adjacent room.

Airborne noise is the more common and occurs, for example, when a TV turned up too loud disturbs people sleeping in bedrooms. It can pass from one room to another along a variety of paths such as open doors and windows, openings in walls separating the rooms, stairwells, or heating and air-conditioning ducts.  Airborne noise can be generated and pass through flimsy structures such as thin walls or even floors or ceilings into other rooms and close apartments.

Structure-borne noise occurs when the building structure itself is made to vibrate; for example, a washing machine in contact with a wooden floor, a saucepan falling to the kitchen floor, and the impact of footsteps on hard floors.