A4 Burgerveen – Leiden Road Tunnel, Holland

The A4 motorway is an important road between Amsterdam and The Hague. Due to congestion, the motorway is being widened from 2 lanes. This resulted in extensive planning on minimising the environmental impact from the development, one of the main concerns being the impact the new traffic will have on noise levels for local residents. It was decided that the road would be recessed into the ground with a partially open ceiling. While this obscures the direct sound path between the source (road traffic) and receivers (local houses), if left untreated, the reverberating sound field would leave complex reflective paths for the sound.

This could be particularly troublesome in the low frequencies, where sound is diffracted the most around the edges of the ceiling, exposing residents to unacceptable noise levels.

After extensive development, Quietstone, along with our partners in fixing engineering and metal work; Van Campen Aluminium, were awarded the contract to line the tunnel with acoustically absorbent panels on a bespoke mounting framework. One panel for the wall, and a lighter version for the ceiling.

The system provides high broadband sound absorption, with high fire safety, stone-like durability and a range of colours to add an aesthetic bonus to the installation. 

Mounting

The fixing for the wall mounted panels includes vertical steel C-sections with bespoke brackets to quickly fix the panels. These sections also include supports for mineral fibre slabs which add to the acoustic performance. Panels are mechanically fixed, with plugs of the same material used to fill the fixing points. The ceiling utilises a very similar system, only the mineral fibre is pinned against the concrete, and the panels have more fixing points. 

“Noise pollution is one of the most prevalent sources of environmental complaint in the European Union.”

– Rok Ho Kim – Occupational health scientist at the World Health Organisation (WHO) Regional Office for Europe 

Technical information

Physical properties
Standard size: 1000 x 600 x 30mm
(other sizes used to t around services)

Weight
FR30 – 37.5kg/m
FR30L – 22.5kg/m

Fire resistance
Tested by Efectis Nederland BV for tunnel re safety.
The test involves exposure of a full wall construction
to 1150°C for 2 hours and panels must not
disintegrate or exceed …. °C in the rear cavity

Impact resistance
EN 1794-1 ‘Road trffiac noise reducing devices – non
acoustic performance – impact of stone’: “Elements
appear to show no visual damage.”

Freeze / thaw resistance
EN 1338 – Class 0

Acoustic performance

The setting

As you can see from the picture below, the motorway cuts through a fairly built-up area. Notoriously flat in plane, Holland has a large demand for noise barriers as it can be difficult to position new roads in areas where the surroundings will provide natural noise reduction. In this case the road was initially recessed down to break the direct sound path to the residents without the need to use large barriers which can obstruct views. Unlike light however, sound energy can bend around objects so by reducing noise build up, our panels make the design much more efficient.