If people respond to what the person on the mic is saying, then the problem has to do with you. If not, its esf. I think you can activate voice support somewhere in the options menu for esf (on steam).
I think its a metter of a cvar like most all other problems...
Mister Satans' usefull pack sets a botton to take it on or off
off to avoid lags and on when wanted\needed
just try to install it to see whats this cvar all about