The success to an inaudible HRV system lies in a well engineered HRV units, a good design and sufficient silencers or otherwise called attenuators.
Target values for bedrooms are 25 dB(A) (A-weighted noise pressure level of the unit) and 35 dB(A) for the installation room.
We recommend for every project to have sufficient silencers at the supply and extract outlet of the HRV unit installed. Silencers at the exhaust and sometimes the intake are at times necessary when the surrounding area is very noisy or sensible to noise.
Depending on the kind of ducting, we also recommend cross-talk silencers between the bedrooms, study and other rooms which need to be extra quiet. Due to the nature of semi-flexible systems, where all ducts come together in distribution boxes, these cross-talk silencers are normally not necessary.