To quote one of the notification e-mails about the system:
The purpose of the SOS is to transmit voice intelligible emergency messages and alert tones to the outdoor campus environment during crisis events.
I do believe that a "voice intelligible" emergency message is one which is intelligible to voices. At best, it might be a message which is intelligible as a voice. I don't think it can really mean what they want it to mean: an intelligible voice emergency message. See: "human readable".
Perhaps I'm suffering from a bracketing error, and they mean it's a
[ voice [ intelligible [ emergency message ] ] ]
but based on the rest of the e-mail, it seems pretty clear that they mean it's a
[ [voice [intelligible] ] [ emergency message] ]
It just can't mean what they want it to mean.