What is an acoustic ventilation box?
An acoustic ventilation box is an elongated box above a window or door that lets outside air in while damping noise from outside. In Dutch it is called a “suskast”. Inside the box the air takes a detour past sound-absorbing material such as mineral wool or acoustic foam. Sound loses much of its energy along that path; air still gets through.
These boxes are used mainly in homes along busy roads and railways and near airports, where an ordinary trickle vent lets in too much noise. When the sound insulation of a facade is calculated, the ventilation opening counts too, and an open vent is often the weakest point. In the UK the same job is done by acoustic trickle vents and through-wall acoustic ventilators.
In practice
- Compare the attenuation. Manufacturers state it as Dn,e,w in dB, measured in the open position. Only compare values measured the same way.
- Check the airflow. Attenuation and airflow pull against each other. Make sure the box supplies enough air for the room behind it.
- Seal it in airtight. Gaps between box, frame and wall let noise and draughts bypass it. Seal the joints.
- Keep it clean. Dust reduces airflow. Clean the flap and grille regularly as the manufacturer advises.
- Get it designed. In noise-affected locations an acoustic consultant should calculate the facade.
Common mistake: fitting an acoustic box but forgetting the rest of the facade. Single glazing or leaky windows will still let in plenty of noise.
Related terms
- Acoustic trickle vent
- Natural ventilation
- Sound insulation
- Mechanical ventilation
- Balanced ventilation
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