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HVAC attenuators


Acoustic silencers to reduce the noise transmitted through air ducts and through openings for the ventilation of enclosures and industrial buildings (facades of industrial buildings, facades of facilities enclosures). The principle of attenuation is the sound absorption by means of an absorptive material (rockwool, fiber-glass).

These silencers, normally known as “absorptive silencers” or “parallel baffle silencers”, are acoustic filters made on metal (normally sheet steel or aluminum) with rectangular or circular section. Absorptive silencers are composed of a set of parallel baffles made of fireproof sound absorbing material.

The main applications of this kind of silencers are:

  • Systems of forced ventilation of air: fans and extractors.
  • HVAC systems: air conditioners, cooling towers, heat pumps, boilers.
  • Ventilation and air conditioning of enclosures

These types of silencers are specially design for:

  • Noise control in medium and high frequency with attenuations between 15 and 50 dBA.
  • A determined air flow rate. Our designs have not physical restriction in order to work within a wide range of flow. Our designs are modular and are not limited by transport or installation options.


Design parameters:

The design of these silencers depends on the following factors:

  • Air flow rate.
  • Incident noise (noise spectrum at the inlet of the equipment).
  • Required attenuation, required noise level at the discharge of the silencer or at a specific distance.
  • Nominal diameter, or inlet section.
  • Pressure drop required.
  • Physical space, weight or materials restrictions.


Customized design:

INERCO can adapt the design of the silencers to the client requirements:

  • Different materials: carbon steel and galvanized steel.
  • Phytosanitary packing.
  • Accessories: flanges, counter flange, nameplate, insulation clips, lifting lugs.
  • Engineering: mechanical calculations (support reactions, vibration modes, stress and maximum strain, fatigue...) and fluid dynamics (calculation of the distribution of pressure, velocities, self-noise and temperature).
  • Possibility of acoustic measurements.


Additional information:

  • Acoustic performance of these silencers depends on the sound frequency of the noise source. Depending on the noise source there will be an optimum type of absorptive silencer.
  • The length of the silencers varies with the attenuation required.
  • Self-noise is a limitation and has to be considered. Self-noise limits maximum attenuation that each model can provide. This parameter depends on air velocity and the aerodynamic design of the silencer.
  • The installation of the silencers is very important factor to minimize turbulences caused by elbows and transition pieces. Aerodynamic turbulence may reduce or modify the acoustic performance.
  • Silencers increase the pressure drop of systems and must be considered as a restriction in the design.
  • Air temperature affects silencer performance.
  • Quality of materials used in the manufacturing of the silencers affect the solution lifetime.
  • In order to optimize the selection of the silencer, we recommend our technical support.