An estimated 360 million people around the world suffer from hearing loss, yet relatively few people seek treatment.

Hearing aids can cost thousands of dollars, but there are cheaper alternatives. Over-the-counter sound amplifiers can be bought online or in drug stores for a much cheaper price. But beware: new tests have shown some may do more harm than good.

Experts at Consumer Reports looked at some of these affordable, over-the-counter sound amplifiers. Most were a fraction of the price of prescription hearing aids, with some costing less than $75.

But the researchers say be careful with these penny-saver models.

"So, we found that actually the really cheap ones aren't that effective at helping people with hearing loss and more importantly, they could actually potentially damage people's hearing further by over-amplifying loud sounds, like a siren, for instance," said Julia Calderone of Consumer Reports.

Another pricier amplifier, the $300 Etymotic bean, did a little bit better, but it's complicated.

When tested in a lab by a professional, hearing aid researcher it showed promise for people with mild to moderate hearing loss while also protecting against over amplification. Plus, panelists who tried it said it was comfortable and easy to use.

But in real-life situations, reactions to all the amplifiers were mixed.

"They seemed to help with things like TV watching, but they weren't so great at deciphering conversations in a noisy environment," added Calderone.

Which means if you do decide to try an amplifier, be sure to check the return policy before you buy.

And while the over-the-counter solutions may be worth a try, the best thing to do is to see a hearing specialist first, to see if these devices are right for your needs.