Alarm without circuit? Possible?

[ClouDxv1]

Hi, i need some help asap.
I wanna know izzit possible for me to do an alarm without designing a circuit to it?
I mean if i just provide power to the speaker it will sound.
A friend of mine suggest i use 1 thing called 'buffer' but i cant seem to find it in the net.

 

[GrandAlf]

A speaker will only make noise with low voltage AC. If you want to use DC, e.g batteries, you need a piezo buzzer, they usually work on 3-12v and are very commonly available.

 

[roykyn]

use a low power audio amplifier lm386 its cheap and has a single power supply(u can use battery).......and efficient too (cmos).....see the datasheet and use the one tat says Amplifier with Gain = 50.....
https://pdf1.alldatasheet.com/datasheet-pdf/view/8887/NSC/LM386.html

 

[carlosftm]

the simplest circuit that came to my mind is a piezo buzzer, resitor, batery and a switch. If you what to do something like an alarm to detect when a door is opened or closed that is the easiest way.

https://www.futurlec.com/Buzzers.shtml
Some buzzer shown in the futurlec's catalog work within 3 to 28 volts.