I also think historically we think about how the crowds were in the past, we don't probably think of a Tuesday night game where one of Fred's teams beat a bad Texas Tech team by 15. Based on my memories, a similar game against a bottom-half team, mid-week where ISU is a big favorite has probably always had relatively similar environments.
I have not been a consistent season ticket holder, but have been to a fair number of games, with a handful in the last Orr years (though I don't remember them that well). So keep that in mind when I share my opinions, but the loudest I have ever experienced Hilton, or any sports venue, was in year 2 of the Willoughby, Pratt, Cato team vs. KU.
The rowdiest on a per person basis I have ever experienced was last year's game during the winter storm against Houston. It obviously wasn't close to a full house, but probably because it was a night for hardcore fans and the intensity of every minute of the game was off the charts, but the people that were there were amped for 40 minutes.