Music playing out of a horn/strobe. How is this possible?

https://www.youtube.com/watch?v=kJgTcLFLkJM



<LINK_TEXT text=“https://wpdh.com/why-is-this-fire-alarm … can-music/”>Why is This Fire Alarm Playing Mexican Music?</LINK_TEXT>



It’s common for newer Walmart stores to have music playing out of the speaker/strobes, but just how can music be playing out of a horn/strobe?

I’ve seen videos of people who’ve managed to play voice evac messages over TrueAlert horn/strobes (pretty sure it was wheelovefirealarms) alongside other things. i’m not sure how its done but its really cool!

Fun fact: all fire alarms (with the exception of bells) are speakers designed to resonate at a specific frequency. The trick to getting the distinct sound you hear (with the exception of residential smoke alarms) is to use a microprocessor to regulate the pitch, sound, and volume.



For that reason, the Wheelock MT is able to make so many different sounds, and is why the horn component of an EST Genesis will sound like a Wheelock Exceder if you rig it in one.



Now why the particular fire alarm seems to be blasting music? That I can’t tell for certain, but I’m placing my bets that it is electrical noise being played through the alarm itself. Considering how the article did mention radio towers in close proximity to the studio, it’s very possible the radio waves are strong enough to induce noise in the wiring.



All wiring is conductive, and can act like antennas. Because of this, there are two possibilities:
[list=1]

  • []The actual FPL wire is acting like an antenna. In a fire alarm setup, this isn’t a huge issue - many of these signals are not enough to power an actual device. Considering how the fire alarm horn only works off of electricity, the 24vDC going from the FACP is going to overpower any noise and should not affect its operation.[/]
  • [*]The piezo/horn wired up to the microprocessor is the antenna. This is more likely since from the audio it's actually replicating some noise outside of the regular frequency I would hear it to be operating.[/*]
  • [/list]

    As I said before, this isn’t a concern for this particular setup. The only time this would be an actual issue is if there are speakers in the system, which again might not be enough power for you to even hear.

    From working with audio equipment, being able to hear the noise usually becomes more of an issue if you’re amplifying any input sounds. In other words, if your input picks up the noise and you amplify it to a speaker, you’ll be more likely to hear it.

    I agree with the above post. It’s most likely induction from the wiring to the Horn in the Horn/Strobe. I hear it all the time in voice evac systems when you’re at the Amp panel. Most times you can faintly hear the evacuation code from the panel itself.