Bass shaker potential problems

I’ve just brought 4 new Buttkicker Gamer Plus’s. Should they be making a knocking sound? I thought they would be silent and just feel the vibrations?

Also i’m not getting consistent feedback in Asetto Corsa (the only game i’ve set up so far). Sometimes the rears will vibrate when drifting and other times they will not. The wheel locking is slow to kick in (i hear it through my headphones before they start vibrating) and the gearshifts don’t always thud. The idle though does always work. Maybe i need to change some calibration settings?

Thanks in advance