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.
A basic speaker is functionally a copper coil next to a permanent magnet. A hard drive head (although I guess more specifically read arm?) is also a copper coil next to a permanent magnet. So if you push an audio signal through the coil, it vibrates and makes sound. It’s missing the diaphram/cone part of the speaker, so it’ll be very tinny.
If you want to make one yourself, get a broken hard drive, and an old pair of headphones, and connect the wires to the coil and play some music.
https://www.instructables.com/Hard-Drive-Speaker-More-Instructive-Version/