Tunnel Ventilation

Tunnel ventilation attenuation is a crucial element of any tunnel system and essential for operational performance, safety and environmental conditions.  Tunnel systems need effective acoustic attenuation in order to manage noise internally, and to mitigate external environmental impact.

The integration of tunnel ventilation attenuator systems is an important consideration during the initial design phase of any tunnel project – errors and omissions can lead to increase in project scope, variation and significant increased costs. IAC Acoustics is an expert manufacturer in practical and sustainable tunnel ventilation attenuation solutions. We offer a wide range of field-proven attenuator product configurations which enables our team of experts to engineer a turnkey project solution for you.

We cover all aspects and areas of your infrastructure project – from acoustic surveys, technical and structural design through to full project management, manufacture and installation.

Multiple aspects of tunnel design are driven by safety and environmental standards. Understanding these safety regulations and being able to provide a low impact solution is all part of the project evaluation stage. Using natural ventilation where possible, effective attenuation can potentially save significant mechanical ventilaiton and energy costs.

Attenuator System & Design Tools

IAC Acoustics have developed a strong and durable system that has been designed specifically for use in tunnel ventilation projects beyond the standard specification HVAC attenuators. Tunnels produce their own unique and challenging environments – high pressure, unique airflow and corrosive vehicle exhaust atmosphere, all have a significant demand on the life span of the equipment.

Our team make use of Computational Fluid Dynamics [CFD] and Finite Element Analysis [FEA] tools to develop and understand the physics of tunnel ventilation in normal and emergency conditions. This technical analysis provides crucial data to model acoustic performance while informing the impact on the tunnel system during an emergency scenario such as fire. These data driven insights help inform cost effective mechanical solutions, as the preferred option that can be incorporated from the outset in the project scope.

Working with our partners at Avesta Consulting, we can guarantee design and long term performance durability to standards such as AS4100 and AS4991.

Parallel Interlocking Attenuators


This design assumes the tunnel is of rectangular shape and is to be installed into concrete air tunnel without the use of external casing around the splitters.

The attenuator assembly is made up of interlocking rectangular parallel splitter modules whilst all maximum permissible module heights will be verified by FEA analysis during detailed design.  Designs can be orientated either vertically or horizontally

Each splitter module is installed individually with module sizes and all quantities confirmed at the initial design stage. The combination of a stacking process, splitter size and mounting system allow for accurate installation with minimal parts and an on-site fit.

Utilising a tongue an grove fixing system, these attenuators can easily be installed in areas with little over head room for lifting equipment.

This installation method also allows for readily removal and re-installation during maintenance or repair without removing adjacent splitters.  This design is well proven in the field and used for the Sydney Metro and WestConnex projects.


Box Type Attenuators

These prefabricated modular sections means installers are not required to handle individual splitter pieces in confined spaces which provides much simpler installation. This design facilitates a rapid install schedule, e.g. one working day to install a typical 7m x7 m x 7m attenuator.

All splitters are pre-assembled into boxes within the factory and can be immediately installed into the designated openings once unloaded from shipping containers. The maximum module size for this design can reach 2.3 m x 2.3m x 2.3m.  Modules sizes are designed for ease of transport and installation. Module sizes can be adjusted to suit the site requirements at design stage.

Lifting points are provided on all box modules for ease of handling and for horizontal airflow orientation, while reinforcing flanges and stiffeners are found on the sides and top. Slots can also be included in the top flange to suit forklift tines. The box casings are robust to protect the internal splitters during transport and handling during this process

This design is proven infield having been used for Westconnex M4E Parramatta Rd and Underwood Rd Ventilation Facilities.



Talk to us today

Please contact us for advice relating to your new project.

Lan Chen

+61 (0) 2 8781 0420
+61 (0) 434 283 967


IAC Acoustic Projects

We have completed or are currently working on a significant number of large scale infrastructure tunnel ventilation projects, locations as indicated on the map below:

WestConnex M4-M5 – Sydney

Northwest Metro – Sydney

WestConnex M4 East – Sydney

Sydney Metro, Martin Place, Central, Barangaroo, Victoria Cross, Crow’s Nest, and Pitt Street Stations + 2 Dive Buildings – Sydney

M6 Motorway Stage 1 – Sydney

West Gate Tunnel Project – Melbourne

MTRRC – Hong Kong

Thailand Metro Orange Line – Bangkok

Carracus Metro – Venezuala

Dehli Metro – India

WestConnex M4-M5 - Sydney

IAC Acoustics was commissioned to deliver tunnel attenuators for the WestConnex M4 East project Parramatta Road and Underwood Road ventilation facilities – exhaust fan intake and discharge.. The attenuator splitter and casing designs needed to meet the unique operating requirements for the ventilation facility – minimising pressure losses and peak shut-off pressure loading conditions during a fire event.

Our CFD analysis of attenuator splitter gap determined pressure loss characteristics and fluctuating pressure loads, for fatigue assessment.  The structural FEA of attenuator splitter and casing designs considered strength and fatigue loading conditions.

The engineering process ensured compliance with AS 4100 for specified operating and ultimate loading conditions.  Maximising strength with value engineering ensured AS 4991 lifting and casing requirements, helping manage cost and an effective installation process.

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