It's going to be like that, for Ajax fans (or any fans in Europe for that matter) travelling over it's a once in a life time opportunity for a lot of them so they're gonna make the most of it.
For us casual match goers, it's like yeah ok we'll sing here and there but we'll be here again next week so meh sort of thing & I think that's kind of stereotypical now across English clubs....guarentee you PSV fans outsing Arsenal at Emirates, Marseille fans outsing Spurs fans at Tottenham stadium, Sociedad fans outsinging Utd fans at Old Trafford last week.