Protection against noise
Noise produced outside or at some place in a building is transmitted to other places in the building by the air itself and by the building structure.
|| Sound transmission:
A - airborne noise source
B - impact noise source
1 - direct transmission (through air and structures) for airborne noise
2 - reflection (causing reverberation)
3 - flanking transmission (through structures) for airborne noise
4 - direct transmission (through structures) for impact noise
5 - flanking transmission (through structures) for impact noise
The maximum acceptable noise level (A-weighted sound (pressure) level) in the building depends on the activity:
|In rooms in dwellings (living rooms, bedrooms, kitchens)
||30 to 40 dB(A)
|Small offices and meeting rooms
||30 to 40 dB(A)
|Large offices to open, busy offices
||40 to 60 dB(A)
|Hand work (e.g. in factory buildings)
Permanent damage to the hearing system occur above 85 dB(A).
These limits can be respected first by reducing the intensity of the noise sources, and second by acoustic insulation.
Nearby sources of noise
There are several sources of noise around buildings, some of them, such as road traffic or parking being linked to the activities in the building. These sources may disturb the occupants of buildings. Within the HOPE office building sample, occupants of buildings close to a potential noise source such as a busy road, an airport or a car park are significantly more disturbed by outdoor noise than those located in a more silent area.
When such sources are present, the building - in particular its acoustic protection - should be designed so that the indoor sound level remains within acceptable limits.
Internal sources of noise
Internal sources of noise are mainly the activities of occupants, but could also be the building systems. Within the HOPE office building sample, occupants of buildings with natural ventilation are significantly less disturbed by noise from building systems than those in mechanically ventilated buildings.
There are mainly three ways for improving the acoustic protection:
- Reducing the intensity of the noise sources
- Installing sound barriers between the noise source and the occupant
- Increasing the sound absorption in the occupied room.