147
An emergency FEMA alert test will sound Oct. 4 on all U.S. TVs, radios and cellphones
(www.cbsnews.com)
This is a most excellent place for technology news and articles.
My understanding is that this alert is mandatory, and will sound no matter what unless the phone is fully off. You can turn off things like Amber and Weather alerts, but my understanding is that this one (by design) cannot be disabled.