While it was down about 10% in total audience vs. last year's premiere (30.1 million vs. 33.4 million), it fell off by 16% in adults 18-49 (11.6/28 vs. 13.8/22) and by an even steeper 25% in adults 18-34 (9.7/26 vs. 12.9/33). This is not unexpected for an eight-year series, as audiences age alongside their favorite shows, which increasingly find it difficult to add new, younger viewers along the way.

The "Idol" producers have made some tweaks to the format this season in an attempt to stave off more audience erosion. Among the changes was the addition of a fourth judge, Grammy-nominated songwriter Kara DioGuardi, who bowed last night.

"Idol" will air another two-hour audition episode tonight before eventually settling into its familiar pattern of a one-hour performance episode on Tuesdays and a one-hour results show on Wednesdays.