Noise Control - Circular Duct Attenuators - S / P Series

  Download PDF


S / P Series


These notes apply to both the open and pod type attenuators.
The units are rigidly constructed and consist of an outer cylindrical galvanised steel casing, lined internally with nonhygroscopic and incombustible soundabsorbent material. This material is retained by an inner perforated metal cylinder.
An impervious lining of the acoustic infill can be provided to prevent the ingress of moisture or grease. There is a small performance penalty in high frequencies when an impervious lining is fitted. Refer to our Sales Engineers if more information is required.
Insertion Loss
The values quoted in the table represent the difference between the sound power level (Lw) of a fan and attenuator combination and that of the fan alone.
To ascertain the sound power level of a fan fitted with an attenuator, the insertion loss should be subtracted from the sound power level (Lw) rating of the fan across the octave band centre-frequency spectrum quoted in the fan characteristic data (obtainable on request).
The fan sound power, Lw, ratings and attenuator insertion loss apply to in-duct operation and where an attenuator is connected between the fan and duct system.

Rectangular Attenuators
Whilst circular attenuators provide a convenient form of attenuation when used with axial flow fans and have the added advantage of minimising noise break-out, it is often more economical to consider standard rectangular attenuators.
Please refer to the pages G-6/10 for details of these.
Purpose-designed attenuators can be supplied for particularly demanding applications requiring performances or construction beyond that provided by our standard product.

Suggested Specification
Attenuators shall be as designed and manufactured by Elta Fans and shall have the performances as scheduled. The casing and end flanges shall be constructed from high quality galvanised mild steel sheet. The end flanges shall be match drilled and tapped to suit the fan flanges and facilitate installation.
Attenuator pods, where fitted, shall be adequately supported and be fitted with a nose cone on the inlet to minimise noise regeneration and pressure loss.






Technical Data