this post was submitted on 23 Feb 2026
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I'm asking not specifically about smoke detectors but any device that beeps but does not make any other, non-beeping sounds. Examples include microwaves, the timers on ovens, the fare system on a bus when you give it your fare, the little beepy heart monitor things in hospitals and old-school digital watches. These things beep but they seem to only beep; they do not make any other, non-beeping sounds.

So my question is: how do these things beep? It must be a speaker right (?), and if it is a speaker then why do these devices never make any other sounds other than beeping? (Because presumably speakers have a greater range than just a few beeps.) Or do these devices have specialized speakers that can only make a few sounds? If so, how do these speakers work?

I'm not sure if I articulated this very well but hopefully that makes sense.

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[–] gedaliyah@lemmy.world 24 points 2 days ago (2 children)

Usually it's not exactly a speaker, but it does involve a controlled moving diaphragm. In a piezoelectric buzzer, a current applied to the diaphragm causes it to oscillate, and the size and shape of the diaphragm determines the tone AFAIK.

It may be theoretically possible to engineer such a device into a rudimentary speaker. I mean, people have done it with Tesla coils and player pianos, so hey, anything is possible?

[–] ageedizzle@piefed.ca 2 points 1 day ago

Interesting. I’ve never heard of a piezoelectric buzzer before. This is the answer I was looking for. Thanks! 

[–] CameronDev@programming.dev 5 points 2 days ago (2 children)

You can also make hard drive heads play music. Poor quality music, but music.

Multiple piezoelectric buzzers could probably play a tune if you tune them to individual notes. Not sure how to tune them, but probably cutting them, or putting bluetak on them would alter their note.

[–] ageedizzle@piefed.ca 2 points 1 day ago

You can also make hard drive heads play music.

How does this work?

[–] slazer2au@lemmy.world 2 points 2 days ago (1 children)

Don't forget floppy drives

[–] CameronDev@programming.dev 1 points 2 days ago (1 children)

Never tried floopy drives, good acoustics?

[–] slazer2au@lemmy.world 3 points 2 days ago

Have you not seen Flopatron?

Apologies for the YouTube link but I don't think he posts things anywhere else.

https://www.youtube.com/@PaweZadrozniak

[–] Fermion@mander.xyz 14 points 2 days ago (4 children)

https://www.labdarna.com/en/understanding-piezo-buzzers-how-they-work-and-how-to-use-them-in-electronics-projects

They use piezo buzzers which work differently to most speakers. I would guess that the units used in smoke alarms and microwaves generally have integrated drivers that only operate at a single frequency. However, it is possible to drive piezo discs at different frequencies. Their ouput will always approximate a sound wave though, so don't expect to be able to use them like a normal electrodynamic/ voice coil speaker to play arbitrary sounds.

[–] Ephera@lemmy.ml 3 points 2 days ago

I would guess that the units used in smoke alarms and microwaves generally have integrated drivers that only operate at a single frequency.

Yeah, you could more easily create a rhythm than a full melody. If you get a few devices, which beep at different frequencies each, you could do a lot more by having them beep in succession and in intervals.

Of course, this requires that they're roughly in tune, which may not be the case at all. 🥴

[–] Beacon@fedia.io 2 points 2 days ago (1 children)

Depending on how briefly they can be triggered i wonder if it could be fired in a controlled enough temporal pattern to create recognizable notes. Human hearing goes down to 40 cycles per second, so if it can fire in burst of less than a 40th of a second then that could work

[–] Fermion@mander.xyz 2 points 2 days ago* (last edited 2 days ago)

The link I included in my comment goes over driving one in recognizeable notes to play the nokia tune. It's worth a read if this concept interests you.

[–] ChaoticNeutralCzech@feddit.org 1 points 2 days ago (1 children)

Piezo buzzers have a resonant frequency they're strongest at. Two-pin piezo disks need driving at the desired frequency. Three-pin provide a phase-shifted feedback to the driving transistor to keep oscillating at the resonant frequency. Some include that whole circuit inside their housing so they have just 2 pins but those are for DC power, only the volume can be somewhat adjusted by changing the input voltage.

[–] Creat@discuss.tchncs.de 1 points 2 days ago

The only ones I've ever used myself area is the DC variety. Apply power: beeeeep; stop applying power:

I don't know why idea are more commonly used in consumer electronics.

[–] db2@lemmy.world 1 points 2 days ago (1 children)

You can if the buzzer signal is only used to trigger a secondary circuit that does what op is looking for.

[–] dddontshoot@lemmy.world 2 points 2 days ago

That's what I would do. Hook jumpers from the buzzer to the play button of an mp3 player. That way if the music system fails, the buzzer still wakes you up.

[–] lovely_reader@lemmy.world 3 points 1 day ago (1 children)

Beeps don't usually come from a speaker, no. You might find this old ELI5 about electronic sound interesting.

[–] ageedizzle@piefed.ca 1 points 1 day ago

Linking to Reddit on Lemmy is blasphemy. (But thanks for the link lol its informative) 

[–] Otherbarry@lemmy.frozeninferno.xyz 4 points 2 days ago (1 children)

I don't have any answers - but now I wonder if your idea would be easier when working with one of the fancier smoke detectors with voice alerts. Those have pre-recorded voice alerts that "speak" when an alert occurs, rather than beeping. Those pre-recorded messages must be stored somewhere in the smoke detector.

[–] thesohoriots@lemmy.world 2 points 2 days ago

Putting in a request now for the intro noises from Korn’s “Twist.”