D-Duct™ Acoustic Diffuser Attenuators

IAC Acoustics designs D-Duct Diffuser Silencers (DDS) for installation at the outlet of vane axial fans. The combined interior diffuser cone and exterior square jacket casing make these units into aerodynamic regain devices as well as silencers. The DDS is an effective inlet cone and silencer.

The D-Duct Diffuser Silencer offers the following benefits:

  • Combined silencer and diffuser – all in one
  • Excellent acoustic performance characteristics
  • Permits silencing where it is most effective
  • Reduces pressure drop
  • Easy to handle and install
  • Certified performance
  • Available in sizes to match directly a manufacturer’s fan sizes

Typical Uses of IAC Diffuser Silencers

Diffuser silencers are suitable for many different types of applications and markets that include:

  • Tunnel Ventilation
  • Air Handling Units
  • Shopping Centres
  • Schools
  • Sports Facilities
  • Hospitals and many more

Diffuser Silencer Range of Products

IAC offers the following range of diffuser silencers:

  • FLAKT for variable vane axial fan discharges
  • JOY for controllable pitch vane axial fans
  • BUFFALO for controllable pitch vane axial fans
  • WOODS for varofoil variable pitch vane axial fans

Materials and Construction

The rectangular jacket outer casing of the Diffuser silencer is from lock formed galvanised steel. The internal diffuser cone is from galvanised perforated steel.

Diffuser silencers include an internal cone of consistent diameter along the entire length in the direction of the airflow. The core diameter is selected based on the adjacent hub diameter or, in the case of C-frame mounted motors, the motor frame size for the respective fan system on which the diffuser silencer is installed. The core is from galvanised perforated steel in the same gauge as the internal diffuser cone. The core is supported by a minimum of three radial attachment brackets installed on 120-degree angles to each other to provide uniform support.

End Connections: 100mm long sleeves are standard. When noted, flanges are welded to the sleeve to form a flange connection.

For units where the minimum diffuser cone diameter is 914mm or greater, an additional support rod is fitted between the radial bracket and the sleeve to prevent from being exerted on the internal core by the airflow of the fan.

All welds are touched-up with zinc-rich paint after fabrication by the manufacturer. The internal core and the rectangular outer jacket of the diffuser silencers are filled with inorganic mineral or glass fibre of a density sufficient to obtain the specified acoustic performance. The fill is packed under not less than 5% compression to eliminate voids due to vibration or settling. The fill material is inert, vermin and moisture proof. Combustion ratings for the silencer acoustic fill when tested in accordance with ASTM E84, NFPA Standard 255 or UL No. 723 are not greater than the following:

  • Flame spread classification 20
  • Smoke development rating 20
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