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Determining Acoustic Performance
The specifier is concerned with eliminating or reducing noise between one area and another – the source area to the receiving area. Before a specifier can determine the choice of doorset, the following considerations should be made.
• What is the noise level in the source area
• What level should this be reduced to in the receiving area
• What is the performance of the wall separating these two areas
• What proportion of the wall area does the doorset occupy
Approved Document E 2003 provides guidelines for rooms that will be used for residential purposes.
A doorset must have a minimum sound reduction index of 29dBRw (measured in the laboratory according to BS EN ISO 140-3:1955 and rated according to BS EN ISO 717-1:1997). This means that multi-occupational buildings e.g. flats, apartments, student accommodation and hotels must meet this standard. It is also recommended that potentially noisy parts of the building e.g. function rooms or the bar, should preferably have a lobby area, double door or high performance doorset to contain the noise.
Acoustic Conditions in Schools
Building Bulletin 93 highlights the need for good acoustic performance in schools. It states the requirements as follows;
Teaching and learning areas 30dBRw Music rooms 35dBRw
Orbis acoustic doorsets can be supplied from 8dBRw to 42dBRw in singles and pairs, and factory glazed.
Threshold seals are essential to maintain the acoustic performance and can be achieved by either drop down seals or wiper seals with a timber, rubber or aluminium threshold (see below). Overall acoustic performance depends on the elimination of all routes of sound penetration, therefore the gap between the back of the door frame and the wall must be well sealed either with mastic or mineral wool.
Rw is the weighted sound reduction index and is a single figure value which characterises the acoustic performance of a partition or partition element, taking into account frequency (or pitch) dependency. Test results are generally for single leaf doorsets. A small reduction in the dBRw rating can be expected for pairs compared with single doors. Astragals and rebated meeting stiles will be required to achieve sound reduction levels.
Seals & Threshold
To maintain a ‘gap-free’ installation the drop down seal or threshold must be aligned accurately. The drop down seal must be adjusted after fitting the door in the frame.