Sound attenuation

[Post and beam]

If distribution box's are used, like these Ubbink Mechanical Ventilation Heat Recovery Ducting Manifolds 8 Port (brinkhrv.com) do they perform the job of sound attenuation or are these also still needed inline somewhere upstream?

[Dreadnaught]

@Post and beam, I have used that manifold on the supply side of my system (on the return-side, I use a smaller Ubbink manifold). These manifolds come with sound attenuation sponge pads that are inserted inside.

 

Before the manifolds, on the larger diameter ducting (160mm Aerfoam) connection to the appliance, I have in-line flexible sound attenuator on both supply and extract.

 

My system is effectively silent from the bedrooms. It is performing very well.