2 to 12V DC Piezo Electronic Buzzer Alarm Electric Security Siren Horn 120dB@12VDC

I cut the connector tip off, and touched the leads to a rechargeable AA battery (1.2V) it was loud enough to be heard. Then I tried an alkaline AA (1.5V). I was surprised that it was noticably louder. The I tried 3.7V 18650 Li-ion battery. That was loud enough to hurt the ears. If I use 5V on it, it just might be too loud for my project!

I don't know how they can get such a loud sound out of such a small package but this thing delivers.Be very careful when testing this, it is loud enough to damage your hearing when close to it. Makes an excellent burglar alarm, should drive them away. Put one of these in every room of your house and they won't be able to tolerate being in there.I almost took off a star because of the plug and no documentation. But simplest is to just cut it off - however that would prevent you from returning it if you decided it wasn't loud enough ha ha. Anyway I found that tip is positive and the sleeve is negative. It survived having the voltage reversed.I only tested it at 12 volts. If it is too loud for your needs then you should be able to reduce the voltage for less volume.

I bought this as part of a DIY FloodLight system that I'm building. This will be the siren that I will be able to trigger, either by motion or remotely. I had no idea what to expect really. I received it and took it out of the box and was impressed with the build quality - I was expecting something much cheaper feeling. For the price it's actually well constructed. Next, being impatient, I just grabbed a used AA battery (maybe it had ~1.2V charge on it) and just connected both ends of the siren to it (after snipping off the 3.5mm jack connector - save it for later if I need it). Even at 1.2V it had decent volume and was good to alert someone indoors in the same vicinity. Probably not going to hear it out doors but I was impressed that even at 1.2V it was a respectable "noise" level. I then got out my power generator and connected it up and started cranking the voltage up - after around 2.2V it became VERY loud. I increased it to 3.3V (which would be the output level of my esp8266 mcu) and it was VERY LOUD, almost to the point where i needed some ear protection. My wife started nodding - yeah, that's definitely going to frighten away anyone nosing around our front porch. I stopped there because I was indoors. I'm shuddering to think (in a good way) how loud this will get at 5V, or even the full 12V. So very pleased with this unit, so pleased that right after this review I'm going to buy another 1-2 units. It's nice to know I could potentially power it from a single AA battery all the way up to a full 12V. Highly recommend!

As I stated above, I found some of the comments funny but most of them appear to be spot on. I am using this little thing as an added sound effect to my pipe organ (yes, pipe organ!) For that reason I need to limit the power to 5v dc. Yes it's plenty loud if not annoying at 5v never mind 12 which I do not plan on ever using. Again all depends on where it gets situated and installed.

We love these! We had family friends experience a water leak and a great deal of damage to their house. We bought these along with a adapter to convert to a traditional outlet plug. We use them with Wyze leak sensors and Wyze smart plugs. Now if there is a detected leak under the kids sinks, sump pump, toilet, kitchen sink, hot water heater, etc the a Wyze app rule turns on the plug for one minute and activates this very loud siren to alert us to the leak! I’m sure there are many other uses too that you can think of! If it is too loud you can dampen with a washcloth, or about five Kleenex or a few paper towels over the top secured with rubber-band!