Motivated by the comment above, I looked up 24.4.2.1 in NFPA 72 and found that it also says that the tone shall be the emergency evacuation signal specified in 18.4.2, that is, the Temporal 3 pattern. This is present at least as far back as the 2010 edition. So, it would seem to me that voice evac systems are in fact required to use a Temporal 3 tone. What I don’t understand then, is how come there are so many voice evac systems installed within the last decade that use non-Temporal 3 tones, such as Slow Whoop. Am I interpreting the code wrong, or are all those systems violating the code?
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Not necessarily. Some jurisdictions have not yet adopted those editions of code (eg. there’s a town I know of that still uses the 2002 edition of NFPA 72) or have their own additional codes that supersede NFPA.
When a jurisdiction adopts an NFPA code, they can choose to adopt the whole thing in its entirety or they can adopt it with their own changes thrown in. The latter is usually what ends up happening. So, some jurisdictions write that they want xyz in their voice evac tone instead of temporal-3, or they want continuous for their horn-strobes. They are totally allowed to do this, because NFPA codes are really just standards.
When you get to some cities like Las Vegas or Chicago, those places have very stringent local codes that are far more specific than any NFPA code, and those codes take precedence over NFPA.