Hi I don't know if this will help but I use this code to remove ambient generic sounds from map it also unprecaches them, the code is Connors if I remember correctly. Maybe you'll manage rewrite this code to only remove those sounds which are unnecessary.
PHP Code:
#include <amxmodx>
#include <fakemeta>
#include <hamsandwich>
public plugin_precache( ) {
RegisterHam( Ham_Spawn, "ambient_generic", "CAmbientGeneric_Spawn" );
}
public CAmbientGeneric_Spawn( ent ) {
set_pev( ent, pev_message, 0 );
return HAM_HANDLED;
}