Principal Rodriguez had important announcements. New lunch schedule. Updated dress code. The spring musical. She stood at the podium in the cafetorium — a space that was a cafeteria Monday through Thursday and an auditorium on Fridays by virtue of folding chairs and determination. The room had vinyl tile floors, cinder block walls, a flat drywall ceiling at 4 meters, and acoustic treatment consisting of exactly one motivational poster.

She began speaking. Row one heard her clearly. Row three was straining. Row six had given up and pulled out phones. Row ten — the 8th graders — never had any intention of listening but now had a legitimate excuse. The PA system consisted of two vintage speakers on the wall that produced sound in the same way a kazoo produces music: technically, but not usefully.

The STI at mid-room measured 0.35. The combination of high RT60 (2.1 seconds), ancient speakers with a frequency response that rolled off sharply above 4 kHz (taking all consonant clarity with it), and an ambient noise floor of 58 dBA from the kitchen next door meant the principal's words were technically present in the room but informationally absent.

Cafetoriums combine every acoustic disadvantage of cafeterias (hard, cleanable surfaces) with every acoustic requirement of auditoriums (speech intelligibility). They excel at neither.

The Moral: If students can't hear, they won't listen. Measure STI with SonaVyx STI and set a minimum target of 0.50 for speech venues — then invest in speakers, treatment, or both.