Design a rectangular splitter attenuator to suit your duct run. Set the case size, length and splitter arrangement, choose flanged or round spigot ends, and see an indicative insertion loss across eight octave bands alongside pressure drop and a live price. Explore the 3D model, export a DXF and send the design for a confirmed fabrication quote in one click.

What a duct attenuator does

An attenuator, or duct silencer, absorbs fan and airflow noise travelling along ductwork before it reaches occupied rooms. Inside the casing, acoustic splitters lined with sound absorbing infill divide the airway into narrow channels: sound energy is absorbed as it passes, while air continues through. Attenuators are the standard fix for fan noise in MVHR systems, air handling plant, kitchen extract and any system where a duct connects a noisy machine to a quiet room.

Balancing attenuation against pressure drop

Attenuator selection is always a trade. Narrower airways and longer casings absorb more sound, especially at low frequencies where fan noise is worst, but they also add pressure drop that the fan must overcome, which itself generates noise and energy cost. The configurator shows both sides of the trade as you design:

• Insertion loss across eight octave bands, 63 Hz to 8 kHz, so you can see how the attenuator performs against the frequencies that matter for your noise problem, not just a single headline figure
• Pressure drop at your design airflow, so the fan selection stays honest
• Free area of the splitter arrangement, the underlying driver of both

Acoustic figures shown in the browser are calculated from an indicative model and are labelled Estimated. When you request a quote, our server checks the configuration against tested performance data where available and the figures upgrade to Confirmed. We are deliberate about that distinction: indicative for design exploration, confirmed for the order.

Configuration options

• Case dimensions and length to suit the duct run and available space
• Splitter number and thickness, setting the airway widths
• End connections: flanged rectangular for duct matching, or round spigots for spiral systems
• 3D viewer with touch controls, so you can check the splitter arrangement and connections visually
• DXF export of the geometry for coordination drawings

Fabrication follows BESA DW/144 conventions, manufactured in the UK.

Who this tool is for

Installers solving a noise complaint on an existing system or quietening an MVHR run into bedrooms. Consulting engineers doing early acoustic selections with visibility of octave band performance rather than a single number. Contractors pricing attenuators at tender with a real configuration instead of a provisional sum.

Frequently asked questions

What is a duct attenuator? A duct attenuator, also called a silencer, is a section of ductwork containing sound absorbing splitters that reduce fan and airflow noise passing along the duct. Air flows through narrow lined channels between the splitters, which absorb acoustic energy across the frequency spectrum.

How do I choose the right attenuator size? Start from the noise reduction you need by octave band, then find the shortest attenuator that achieves it within an acceptable pressure drop at your airflow. Longer cases and narrower airways attenuate more but resist the airflow more. The configurator shows insertion loss, pressure drop and free area together so you can find the balance.

What is insertion loss? Insertion loss is the reduction in sound power the attenuator provides, measured in decibels per octave band, comparing the system with and without the attenuator installed. It varies strongly with frequency: attenuators typically perform best in the mid frequencies and require more length to deal with low frequency fan rumble.

Where should an attenuator be installed? As close to the noise source as practical, typically immediately on the fan or air handling unit connection, and always between the fan and the occupied space. On MVHR systems, attenuators are commonly fitted on both the supply and extract sides, and crosstalk attenuators are used between rooms sharing a duct.

Are the acoustic figures in the configurator guaranteed? The in-browser figures are an indicative acoustic model, clearly labelled Estimated, and are appropriate for design exploration. When you request a quote the configuration is checked server side against tested data where available and the performance is confirmed. Order documentation states the basis of the figures.

Related tools

• [Duct Sizing Calculator]: size the run the attenuator sits in, including its pressure drop
• [Part F Ventilation Calculator]: MVHR duties that often drive attenuator selection
• [Plenum Box Configurator]: lined plenums as the last line of noise control at the terminal