Insertion loss depends on the line of sight
A noise barrier works by forcing sound to diffract over its top edge. The extra path length the sound must travel — the Fresnel number — determines the insertion loss. Break the line of sight between the source and the receiver and you typically gain 5 dB; every additional metre of effective height adds roughly 1.5 dB, with practical designs plateauing around 15–20 dB.
On one UAE expressway section OSGT modelled and supplied, roadside levels of 92 dB(A) were reduced to 63 dB(A) behind the installed system — a 29 dB reduction achieved through combined barrier height, absorptive facing and correct end-treatment.
Length matters as much as height
Sound flanks around barrier ends. As a rule of thumb the barrier should extend at least four times the source-to-receiver distance in each direction beyond the receiver, or be returned at the ends. A short barrier directly in front of a villa will disappoint the client no matter how tall it is.
Absorptive vs reflective panels
- Reflective (transparent acrylic, sheet steel, concrete) — cheapest per m², suitable where there is no opposing façade or opposite carriageway to reflect towards
- Absorptive (perforated metal with mineral wool core, timber composite) — required where receivers exist on both sides, in cuttings, or where reflections would raise levels opposite
- Hybrid metal + timber — absorptive performance with a softer visual treatment for residential and landscaped corridors
- Solar-integrated — barrier plus PV generation on long infrastructure runs
UAE-specific design factors
- Wind loading: design to the project's basic wind speed; coastal Dubai and Abu Dhabi sites regularly govern post and footing sizing over acoustic requirements
- Corrosion: specify marine-grade coatings or aluminium in coastal and sabkha zones; hot-dip galvanising alone often under-performs
- Sand ingress: perforated facings need an inner tissue or fleece so absorptive infill does not clog and lose performance
- UV and surface temperature: acrylic and polymer components must be rated for sustained high surface temperatures
- Maintenance access: allow removable panels at the base for cleaning and service crossings
A practical selection sequence
- 1. Measure or model existing levels at the receiver, day and night
- 2. Set the target — project brief, Dubai Municipality or Abu Dhabi EAD limits
- 3. Calculate the required insertion loss (target minus existing)
- 4. Model barrier height and length to achieve it, checking flanking paths
- 5. Choose absorptive or reflective based on the reflection geometry
- 6. Select the panel system for wind load, corrosion class and visual requirement
- 7. Verify with post-installation measurement
Frequently asked questions
How tall does a highway noise barrier need to be?
Most UAE highway barriers fall between 3 m and 6 m. The correct height comes from acoustic modelling: it must break the line of sight from every vehicle noise source to every receiver, then add height to achieve the required insertion loss, which is typically 10–15 dB.
Do noise barriers work for high-rise apartments?
They work well for ground and lower floors. Upper floors retain a direct line of sight over the barrier, so gains fall away with height. For towers, façade treatment — glazing, ventilated acoustic vents and balcony absorption — is usually the effective route.
What is the difference between insertion loss and sound reduction index?
Insertion loss is the measured reduction at the receiver after the barrier is installed, which depends on geometry. The sound reduction index describes only the panel's own transmission performance. A barrier needs a panel index around 10 dB above the target insertion loss so that transmission through the panel does not become the limiting path.
Highway & Railway Noise Barriers
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