They won't. I think we all know that a very high majority arent intersted in supporting the team vocally. Thats the same at pretty much every english club. The difference between us and quite a lot of other clubs is we have no 'end' where like minded fans can gather in large numbers. The manager wont know this, he'll just see it as fans being quiet. Nothing can change unless the club change the current seating plan which would mean turfing out ST holder which the club wont do, but at clubs where this has happened the atmosphere has improved.
So i'm at a loss to what fans who want the atmosphere to improve hope to achieve by keep posting about things being so quiet.