General
The purpose of this section of this document is to protect residents from noise produced from reverberation in common internal areas outside the dwellings. This section as detailed in Technical Guidance Document E, provides guidance on how to limit the amount of reverberation around the common spaces to a level that is reasonable in order to achieve compliance with Part E of the Building Regulations.
Common spaces
The common parts of buildings tend to be constructed with hard durable surface finishes, which are easily maintained. Unfortunately, such surfaces lack the soft open texture which efficiently absorbs sound and so the level of reflected, or reverberated, sound tends to be high in such places and can lead to an unreasonable level of noise for the occupants of dwellings which open directly onto these common spaces.
Whilst another section in this document outlines the inherent acoustic weak point in a separating wall caused by entrance doors opening onto a common area of a building and addresses the acoustic performance of entrance doors, this section deals with ways of reducing the reverberation level at source.
It is relatively easy to increase sound absorption and hence reduce reverberant noise levels by surface treatment with absorbent material. In general, this can be achieved through the application of absorbent treatment to common areas onto which dwellings open directly.
For the purposes of this section the following should be noted:
A corridor or hallway is a space for which the ratio of the longest to the shortest floor dimension is greater than three.
An entrance hall is a space for which the ratio of the longest to the shortest floor dimension is three or less.
Where an entrance hall, corridor, hallway or stairwell opens directly into another of these spaces, the guidance should be followed for each space individually.
Where separating walls, without doors or windows, are adjacent to common areas it would not normally be necessary to treat the common areas, assuming normal usage.
Choice of material
In accordance to the requirements of Technical Guidance Document E the choice of absorptive material should be of an appropriate class that has been rated according to I.S. EN ISO 11654 and should meet the requirements of Part B – Fire Safety.
Methods of satisfying the requirement of Reverberation Control
There are two methods (Method A or Method B) described below that will satisfy the requirement of reverberation control
Method A – Intended for corridors, hallways and stairwells.
Method B – Intended only for corridors, hallways and entrance halls as this method is not suited to stairwells.
Method A
In accordance with the requirements of Technical Guidance Document E in entrance halls, corridors or hallways the absorbent material should cover an area equal to or greater than the floor area, with a Class C absorber or better, rated according to I.S. EN ISO 11654. It will normally be convenient to cover the ceiling area with the additional absorption.
For stairwells or a stair enclosure, calculate the combined area of the stair treads, the upper surface of the intermediate landings, the upper surface of the landings (excluding the ground floor) and the ceiling area on the top floor. Either cover an area at least equal to this calculated area with a Class D absorber or cover an area equal to at least 50% of this calculated area with a Class C absorber or better. The absorptive material should be equally distributed between all floor levels. It will normally be convenient to cover the underside of intermediate landings, the underside of the other landings, and the ceiling area on the top floor.
Method A can generally be satisfied by the use of proprietary acoustic ceilings. However, the absorptive material can be applied to any surface that faces into the space.
Method B
In comparison with Method A, this method takes into account the actual absorption power of the surfaces of the enclosure prior to the provision of additional absorbent material. This allows the amount of additional material which is required to be calculated and directed at the sound frequencies at which it is most needed.
In some cases, Method B should allow greater flexibility in satisfying the requirement of reverberation control and require less additional absorption than Method A. The approach to be adopted for Method B is outlined by the worked example in Appendix C of this document.
Report Format
As detailed in Technical Guidance Document E Evidence that the requirements of reverberation control have been satisfied should be retained in the form of a report or drawing which should include the following:
a) A description of the enclosed space (entrance hall, corridor, stairwell etc.)
b) The method used to satisfy the requirement of requirements, i.e. Method A or Method B
c) The absorber class and the area to be covered
d) Plans indicating the assignment of the absorptive material in the enclosed space.
