Quiet-Duct® Rectangular Attenuators

Quiet-Duct® rectangular silencers are available for conventional applications including low-frequencies. IAC’s range has an acoustic performance specifically engineered for the 63Hz, 125Hz and 250Hz octave bands. Through over half a decade of innovation, our pioneering range of duct silencers are among the highest performing models available.

Our Quiet-Duct® Rectangular Attenuators are in use in many different markets and applications that include:

  • Hospitals
  • Schools
  • Airports
  • Shopping centres
  • Sports facilities and many more

IAC has been manufacturing Quiet-Duct® attenuators for over 50 years, installing thousands of units each year. We test all of our products in our own R&D laboratories to ensure each attenuator provides the correct acoustic performance levels. As a result, all IAC Acoustics Quiet-Duct® silencers provide a guaranteed acoustic performance.

We offer a wide range of Quiet-Duct® attenuators, however, if you have a special requirement, please get in touch.

Product Range

IAC has many different ranges of Quiet-Duct® rectangular attenuators such as:

  • S Range This duct attenuator is the industry standard for maximum noise reduction with minimum silencer length but also provides a standard pressure drop.
  • L Range This model provides the lowest pressure drop while keeping higher insertion losses.
  • SM Range This duct attenuator is a new model to IAC, and was designed and tested to have a duct silencer that provides attenuation between the S type and MS type.
  • MS Range This duct attenuator provides for a medium pressure drop.
  • ES Range The Energy Saver duct attenuator provides the same high level of acoustic performance as an S Type Attenuator combined with a marked decrease in energy consumption.
  • LFS Range The LFS range provides superior low frequency attenuation. When low frequencies are controlling, a type LFS selection often results in a short attenuator length then the equivalent type S Quiet Duct Attenuator.
  • LFM Range The LFM range provides improved low frequency attenuation particularly in the third octave band. When third band performance is critical, a type LFM selection often results in a shorter attenuator length than the equivalent attenuator models.
  • LFL Range The LFL range provides improved low frequency attenuation as well as low-pressure drop aerodynamic performance. It is particularly suitable for environments when the third or fourth band performance is critical at the lowest available pressure drop. The LFL duct attenuator selection often results in a shorter attenuator length than other equivalent models.

Features of Quiet-Duct® Silencers

IAC’s Rectangular duct attenuators have many different features such as:

  • Construction options for our Quiet-Duct® attenuators include galvanised steel, aluminium, or stainless steel.
  • Colour options are available from the extensive RAL colour range, if required.
  • Linings for these duct attenuators are available in Melinex® or Glass Cloth.
  • Hospital specification range includes a honeycomb infill to stop fill migration.

Materials and Construction

The outer casings of rectangular duct silencer modules are made from galvanised steel in accordance with HVAC DW 144 and ASHRAE GUIDE recommended construction for medium pressure rectangular duct work. The seams of the Quiet Duct Attenuator are lock formed and mastic filled.

Internal acoustic elements of rectangular silencers incorporate integral die formed evase entry and exit to minimise pressure drop and self-noise. Interior partitions for rectangular silencers are made of no less than 26 gauge (0.46mm) galvanised perforated steel.

The filler material is inorganic mineral or glass fibre, which is of a density sufficient to obtain the specified acoustic performance and is packed under no less than 5% compression to eliminate voids due to vibration and settling. Materials are inert, vermin and moisture proof.

Combustion rating for the Quiet Duct Attenuator acoustic fill is no greater than the following when tested in accordance with ASTM E84, NFPA Standard 255 or UL No. 723.

Acoustic Performance

Attenuator ratings are determined in a duct-to-reverberate room test facility that provides for airflow in both directions through the test silencer in accordance with applicable sections of ASTM E 477, ISO 7235:1991 and BS 4718-1971. The test set-up and procedure is such that all effects due to end reflection, defectively, flanking transmission, standing waves and test chamber sound absorption are eliminated. Acoustic ratings include Dynamic Insertion Loss (DIL) and Self-Noise (SN) Power Levels both Forward Flow and Reverse Flow with airflow of at least 10m/s entering face velocity

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