I earn a living explaining tech to people, but I have a rather soft voice. That can create some challenges, especially when I want to talk for several hours at a mini maker faire. I did some research on Amazon.com and opted for this portable voice amplifier. It worked very well for my needs at a recent mini maker faire. I was able to speak for several hours without going hoarse. It has rechargeable lithium batteries.
The limitations of this device? Sometimes it squeaks with feedback if you turn up the volume to the highest settings. The device is loud enough for my needs without turning it up all the way.
Another useful purpose for this device is for use at CoderDojo meetings — where children sometimes make presentations about computer programming. At one such meeting I attended, a very bright 2nd grader was explaining about the Python program she is working on. If I had owned this device before her presentation, I would have loaned it to her — and her voice would have carried further back into the room.
I’d strongly recommend this device as a purchase for school and public libraries, as some community members might need to use such a device just once or twice a year — and it might not make sense to purchase the device to own privately for such sparing use.