Acoustical Pack Migration

 Due to the application involved some customers may have concerns over the migration of the acoustical packing used in industrial silencers. “Migration” is defined as the movement of the acoustical packing material from its location within the silencer into the air stream.

 Acoustical packing is mandatory where silencers are used on blowers operating above transition speed. At speeds above transition, blowers generate higher frequency noise that is unable to be attenuated by the standard chamber/reactive silencer. The addition of the acoustical packing removes this objectionable noise before it can impact the silencer shell and cause shell ring. For a more detailed description of transition speed and shell noise please contact Stoddard Silencers, Inc. at (847) 223-8636 (phone), (847) 223-8638 (fax) or via e-mail at

 Packing migration is dangerous in applications such as food, plastics and fine bubble diffuser systems used in waste water treatment, to name a few. Stoddard Silencers has over forty-five years experience in the rotary blower market. It is this experience that has allowed them to design an acoustical packing component to the chamber-absorptive silencer that prohibits pack migration.

 The design Stoddard Silencers uses is a combination of a finely perforated pack retention tube and a long strand, highly flexible acoustical packing material. Our standard packing material is polyester wool that has a temperature limit of 325o F. For applications where the temperature exceeds this limit, please contact Stoddard Silencers.

 When properly selected, installed and maintained, Stoddard Silencers’ designs will not allow packing to migrate. In field studies where Stoddard’s standard design silencers have been removed from service and examined, no pack migration has ever been evident. This is a testament to Stoddard Silencers expert engineering, design and fabrication.

Should there be any other questions regarding acoustical pack migration, please contact Stoddard Silencers at the numbers shown above.