HVAC Attenuators

Rectangular and cylindrical duct silencers from IAC Acoustics provide effective and predictable noise reduction at substantial savings over other methods due to our products being laboratory developed and tested under controlled conditions. To assure this, silencers are periodically tested in our accredited aero-acoustic laboratory. This practice of quality control performance testing ensures that all silencers exhibit catalogued Dynamic Insertion Loss (DIL), Self-Noise (SN), and pressure drop performance data.

Since 1950, professional engineers have specified modular duct silencers from IAC Acoustics with the confidence to control all types of noise sources in air handling systems.


Silencers for Air Handling Systems

The advent of high-performance HVAC equipment has resulted in unacceptably high noise levels both in low and high frequencies. This creates a need for more stringent noise control specifications in air conditioning systems. Performance rated silencers provide the most effective and economical solutions. More reliable noise data has become available from manufacturers of Air Handling components. Therefore, the use of silencers which are accurately rated under operating conditions contributes to the achievement of the desired noise criteria.


Predictable Acoustic Performance

IAC Acoustics’ silencers are rated under operating conditions in the most advanced aero-acoustic R&D laboratory available. Regardless of their size or configuration our silencers are developed, tested, and rated in accordance with the most current industry standards. There is no guess work with hit-or-miss empirically developed calculations or otherwise inaccurately rated silencers.


Duct Lining and Silencers

In most cases, the use of duct lining alone cannot sufficiently attenuate the noise from air handling equipment. The high volume production of quality-controlled standardised components brings our duct silencers within budget of any project. Proper structural design assures a long and trouble-free life.

Attenuator Selection Tool

Specifying and selecting attenuators as part of a larger complex HVAC system requires a significant amount of calculation while managing multiple input variables.  Additionally the outcomes need to give the specifier confidence the system will be effective as its original design intended for air flow, combined with guaranteed acoustic performance.  This requires access to certified laboratory data for attenuators for data input and software to manage the process.

IAC Acoustics has developed its SNAP tool [Systemic Noise Analysis Procedure] which simplifies the design process.  Simply build up the ductwork system and the software will select the correct attenuators without going into lots of complicated Acoustic calculations – we do the number crunching for you.

Functionality includes;

  • Internal or External ductwork calculation variable
  • Noise source selection
  • Noise attenuation requirement, internal/external
  • Duct straights & bends builder
  • Pre-configured IAC Attenuator options
  • Quick-pick option where the software selects models for you
  • Easily visible system success check – green / red 


Save your selections and project history via your account and log-in credentials.  Build up you project portfolio for easy recall – you can end you specifications directly to our sales team for pricing.  We also offer technical and training support on a one-to-one basis.  Please create you account or log in here;


Available for conventional applications including “Low Frequency”, IAC silencers have acoustic performances which have been specifically engineered for the 63Hz, 125Hz, and 250Hz octave bands.

Available for systems requiring a higher degree of cleanliness and hygiene such as hospitals or clean room applications. Linings on the fill material guard against erosion of particulate matter into the airstream. Specific internal construction features protect the lining against chafing or premature failure and are necessary to maintain the rated aero-acoustic performance.

Like our Quiet-Duct®, our Conic-Flow® range has been specifically engineered for the 63 Hz, 125 Hz, and 250 Hz octave bands.

Available for use on axial fan systems. The combined interior diffuser cone and exterior square jacket casing make these units aerodynamic regain devices as well as silencers.

Available as the ultimate solution for ultra-clean environments and corrosive/flammable environments. The complete absence of fill makes our packless silencers ideally suited for hospital, clean-room, pharmaceutical, food, electronics manufacturing, or any other applications where particulate matter or fibre erosion from conventional fill materials could contaminate the air/gas streams. 

Available for small diameter circular duct systems such as fume hoods. However, the packless design of these makes them equally applicable to the types of systems mentioned for the rectangular packless silencers.

Talk to us today

Please contact us for advice relating to your new project.

Gill Budd

+44 (0) 1962 873000
+44 (0) 7905 366843

Duct Silencer Development

IAC Acoustics was founded in 1949, and our first air conditioning silencers were developed in 1950. Since then, we have pioneered the development of performance rated silencers to
ensure quiet air handling systems. To maintain this position of leadership, we operate fully equipped state-of the-art aero-acoustic laboratories. These facilities are not only used for development of new silencers and other noise control products, but also for quality control purposes.

In 1965, for the first time in the noise control industry, we began offering duct silencers with air flowing through them and an accurate acoustic performance rating. IAC introduced the term “Dynamic Insertion Loss” (DIL) to report noise reduction with airflow, and “Self-Noise” to describe the noise generated by the air flowing through the silencer itself. Furthermore, aerodynamic and acoustic performance was measured in one test facility, on the same silencer, and under specific repeatable conditions.


Forward and Reverse Flow

In 1972, we developed silencer Dynamic Insertion Loss and SelfNoise ratings both under Forward Flow (+) and Reverse Flow (-) conditions for rectangular and cylindrical silencers. Since attenuation values are generally higher in the first five octave bands in the Reverse Flow mode compared to the Forward Flow mode, more economical silencer selections can often be made on return-air systems.  HVAC noise control requirements are rarely confined to a narrow low frequency range. The broad band low and high frequency attenuation capabilities of typical passive silencers are practically always required. Also today’s passive silencer selections include ‘Low Frequency’ models offering certified performance. Passive silencers combine low cost, simple installation and maintenance free life time operation to make them the natural choice in HVAC engineered noise control.


Passive Silencers

All of the silencers manufactured by IAC Acoustics are of the passive design as they do not require mechanical or electrical means to function. They do their job very simply by providing a trouble free static means for the dissipation of sound energy by converting it into very minute quantities of heat. Many of the original air conditioning silencers developed by IAC Acoustics in 1950 are still in use today.

Silencer Options

  • Circular spigot ends
  • Slide on flanges
  • Angle flanges
  • Vertical or horizontal splitter orientation
  • Melinex wrapped infill
  • Glass cloth wrapped infill
  • Honeycomb stand-off for Clean-Flow™ silencers
  • Hospital specification – Mylar and honeycomb
  • Casing thicknesses in a range of sizes
  • Double skinned construction
  • Polyester Powder Coating (PPC)
  • Chlorinated rubber paint
  • Construction materials, including galvanised mild steel, stainless steel & aluminium
  • Integral inlet and outlet plenums
WordPress Video Lightbox