Attenuators and Silencers for HVAC applications

Attenuator applications – Attenuators and Silencers for HVAC are typically connected to a specific fan or air handling unit (AHU).  So they are not usually selected until the fan is selected and then must match the dimensions of that specific fan only.

Attenuator designations – Typically this adds ATT- in front of the matching fan designation.

Lined and Unlined – is the same as mylar lined, sometimes just called M or ML or lined or Q-seal.

They have an impervious seal between the acoustic fill and ambient air. They are used in critical applications where the possibility of fibre contamination of the acoustic fill is not allowed. There is a penalty on the acoustic performance in exchange for the certainty that fibre escape is eliminated.

Typical applications for lined attenuators are as follows: –

  • clean rooms.
  • operating theatres.
  • wet environments where attenuators are exposed to the elements.
  • kitchen exhaust systems.
  • applications where workers are sensitive to fibre exposure.

NCC Compliance for Attenuators

Static pressure loss no more than 40Pa – also called Max External Static Pressure

Interpreting Attenuator Dimensions

The Attenuators and Silencers for HVAC diameter or cross-sectional dimension is usually matched to the fan served by the attenuator.  If not, then there needs to be transition duct to connect the attenuator to the fan.

Length is typically a multiple of the cross-sectional dimensions. So typically could be 1D or 2D where D is the diameter of the attenuator. As an example, if attached to an axial fan then the diameter of the attenuator will match the fan and be 1D or 2D long. So a 600mm diameter axial would have an attenuator that is 600 in diameter and 600 (1D) or 1200 (2D) long.

Types of Attenuators and Silencers for HVAC

Podded – means there is an internal section pod in the direct airflow. Circular attenuators have a central cylindrical pod. Rectangular attenuators have a series of dividing splitters.

Podded attenuation can increase the resistance to the airflow and hence increase the static pressure.

Open or Unpodded – This means there is nothing in the centre of the airflow and typically has lower static pressure losses than podded but not as good attenuation.

Cross Talk – these are a smaller flatter rectangular attenuator that comes in L, straight, U and Z shapes to suit the application. Attenuation is on the top and bottom sides only.

Rectangular – these attenuators include splitters that can be either straight or tapered. With tapered provides superior sound performance and is available in lined.

For more information about attenuators for HVAC and industrial applications contact us here.