When my schools alarms go off some of the Ummts sound a bit higher pitched than others and Some just sound like a regular ummt. They sound more high pitched in some of the hallways and my schools system is probably from the 90s. They seem to be random. Idk why some do this. It could be the hallways. Sorry if this topic seems random.
If they sound like smoke alarms, they’re probably U-MHT’s, which are the single-tone version with the 3000 Hz tone.
No i dont think its that it sounds more like a mix between a wheelock ns and a ummt but idk
They sound more like this
There sounds like there is some very weird feedback in that horn.
This is a possibility, but don’t quote this for all situations of this occurrence…
Cerberus Pyrotronics/Siemens offered three horns and horn/strobes in the U-Series body styles: U-MMT, U-MHST, and U-MHU.
U-MMT----We all know this alarm very well. 8 tones, offered first as fixed candela (U-MMT-SXX), then later in a multi-candela configuration (U-MMT-MCS). The horn tones are pitched on G-flat 3. https://www.youtube.com/watch?v=G_2Nm2YABe8
U-MHST----This is also a well-known signal. One obnoxiously high-pitched tone in Temporal (G-natural 7), and the same candela options as the U-MMT line. https://www.youtube.com/watch?v=vmxCQHqiM54
U-MHU----This is a weird crossover between the U-MMT and U-MHST. Multi-candela, but one lower-pitched horn tone. The horn is pitched at A-flat 3, one whole-step higher than the U-MMT signals. This would explain the tone difference and dissonance between the horns. https://www.youtube.com/watch?v=h8juKz0ldY8
All models came in red and white versions (add the suffix “W”…i.e. U-MMT-MCS-W) as well as both wall and ceiling mount configurations (add the suffix “C”…i.e U-MMT-MCS-C or U-MMT-MCS-W-C).
Hope this helps!
Ok thanks that helps 
Yea some of my schools ummts sound different in some parts of the school
I was wondering that.
None of those horns sound the same as the video he posted though, but I’m not sure if that is due to the feedback of that video’s horn.