Noise Control - Rectangular Duct Attenuators - RS / RT Series

Rectangular Duct Attenuators (RS/RT Series)


  • These notes apply to RS and RT type attenuators


  • The units are rigidly constructed and consist of a galvanised sheet metal casing containing a series of centre and side splitters.
  • The casing is provided with Pittsburgh corner seams.
  • End flanges have a red oxide finish and are not drilled as standard unless ordered with matching flanges.
  • The splitters are filled with no hygroscopic and incombustible material.
  • This material is covered with a gauze scrim and then further covered with galvanised perforated sheet metal.
  • Where attenuators are exposed to the weather, all infill material shall be lined with an impervious film to prevent ingress on moisture.
  • See page G-6 for selections from our Q-Seal range.
  • Standard attenuators are suitable for duct pressures up to 1kPa.
  • Attenuators suitable for higher pressures or manufactured from special materials such as stainless steel or aluminium, are available on request.
  • In addition, special finishes such as epoxy coating can be provided.

Insertion Loss

  • The values quoted in the tables are defined as static insertion loss as defined in BS4718:1971, Methods of Test for Attenuators for Air Distribution System.
  • Insertion losses greater than 50dB are not reported as their achievement in practice is difficult.
  • The performance data is based on Australian-sourced and manufactured materials.

Suggested Specification

  • Attenuators shall be as manufactured by Elta Fans and shall have the performance as scheduled.
  • The casing shall be manufactured from high quality galvanised mild steel sheet with Pittsburgh corner seams.
  • Mild steel end flanges shall be provided pop-riveted and sealed to the case.
  • These shall be finished with zinc-rich primer or hot dipped galvanised after fabrication if requested.
  • Acoustic splitters shall have a semi-circular inlet fairing with tapered discharge profile to minimise pressure drop and regenerated noise, like Q-Tech RT series.
  • Where nominated, straight splitter attenuators can be used like Q-Tech RS series.
  • Airways shall be straight and parallel.
  • The infill material shall be either rockwool or fibreglass as specified by the manufacturer.
  • The infill material shall be covered with a gauze scrim to prevent erosion of the fibres, then encased in galvanised perforated sheet metal Where attenuators are exposed to the weather they shall be of the Q-Seal type.
  • All infill materials shall be lined with an impervious film to prevent the ingress of moisture.
  • The infill material when tested in accordance with AS1530.3:1989 shall have the following indices: -
          - Ignitability 0
          - Spread of flame 0
          - Heat evolved 0
          - Smoke developed 0


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