47 CFR § 10.520 - Common audio attention signal.
A Participating CMS Provider and equipment manufacturers may only market devices for public use under part 10 that include an audio attention signal that meets the requirements of this section.
(a) The audio attention signal must have a temporal pattern of one long tone of two (2) seconds, followed by two short tones of one (1) second each, with a half (0.5) second interval between each tone. The entire sequence must be repeated twice with a half (0.5) second interval between each repetition.
(b) For devices that have polyphonic capabilities, the audio attention signal must consist of the fundamental frequencies of 853 Hz and 960 Hz transmitted simultaneously.
(c) For devices with only a monophonic capability, the audio attention signal must be 960 Hz.
(d)
(1) No person may transmit or cause to transmit the WEA common audio attention signal, or a recording or simulation thereof, in any circumstance other than in an actual National, State or Local Area emergency or authorized test, except as designed and used for Public Service Announcements (PSAs) by federal, state, local, tribal and territorial entities, and non-governmental organizations in coordination with those entities, to raise public awareness about emergency alerting, provided that the entity presents the PSA in a non-misleading manner, including by explicitly stating that the emergency alerting attention signal is being used in the context of a PSA for the purpose of educating the viewing or listening public about emergency alerting.
(2) If the Administrator of the Federal Emergency Management Agency (FEMA) or a State, local, Tribal, or territorial government entity becomes aware of transmission of a WEA false alert to the public, they are encouraged to send an email to the Commission at the FCC Ops Center at FCCOPS@fcc.gov, informing the Commission of the event and of any details that they may have concerning the event.
(e) A device may include the capability to mute the audio attention signal.