Types of Blower Silencers

Roots Whispair pressure pulses vs conventional unit

As the impellers of a positive displacement blower rotate, they trap a pocket of air every time they pass by the inlet and discharge connection, creating a pressure pulse.  This pressure pulse presents two issues:

  • Pulsation causes vibration in the piping system
  • The low frequency noise can be a nuisance or even a health concern for people in near vicinity of the blower

Blower silencers are used to reduce this noise and vibration.  Silencers are typically placed at the blower’s inlet and discharge in pressure applications.  For vacuum applications a silencer is typically used on the discharge only.

There are three basic types of silencers used to reduce the noise and vibration generated by the pressure pulse.



The three basic types of blower silencers

Chamber Type Silencers

This reactive type silencer consists of a series of expansion chambers with interconnected tubes.

Chamber Absorptive Type Silencers

Similar to the chamber type, but with an acoustically-packed, sound absorbing section. This packed section is found closest to the blower: at the inlet of a discharge silencer and the outlet of an inlet silencer.

Absorptive Type Silencers

This is a simple, straight-through, packed type. They are used on small, high speed machines that produce significant high frequency noise and relatively mild pulsations.


Available Silencer Series

Chamber Type Series

  • UCIH
  • URDH
  • URDS

Chamber Absorptive Type Series

  • SD, SDY
  • RISH
  • SDH
  • SDS
  • RD, RDY
  • RDH
  • RDS

View Chamber-Absorptive Silencers

Absorptive Type Series

  • U5
  • U2
  • SU5
  • SU4
  • SU3

View Absorptive Silencers

One additional option: Combination Filter / Silencer

One additional option for the inlet side is a combination filter/silencer. These are used on the inlet only and provide filtration and minor noise attenuation. When noise is a concern, it is far more effective to use one of the silencer types above in conjunction with a separate inlet filter, however there are some situations where a combination filter/silencer is an appropriate solution. We carry several series of filter/silencer models including the FS, CCS, and F64 series.


Selecting your Silencer

To select the right silencer for your application you must choose a silencer of the correct type and the correct size (sufficient capacity for the volume flow).  The nominal silencer size need only be based on the gas volume (i.e. the CFM of the gas or air at the operating conditions), however the silencer design must be selected with consideration of the blower size and operating speed.  See our article on Silencer Sizing for more technical details.

At pdblowers, the SD, RIS, SDY, and RISY series are our most commonly used silencers. Browse the silencer models available on our website or Contact our applications team if you need assistance selecting your silencer.

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