Much is made of the fact that especially loud noises over a sustained period will cause permanent hearing damage. One way to compensate for this loss is the hearing aid. We all know that it amplifies sounds to compensate for the ear’s diminished hearing. But just how loud do hearing aids get? Wouldn’t that make the deafness even worse? In other words, can a hearing aid cause damage to your hearing?
Mods,
I spaced.
Please move this to “General Questions”
The quick answer is “no, as long as they are properly prescribed, dispensed, and fitted.”
Hearing aids are regulated devices and are fitted with a prescriptive method that is based on the degree of hearing loss, in addition to other measures. Modern hearing aids will give the greatest gain (amplification) for soft inputs with increasingly less gain (amplification) for louder inputs. Research shows that people with sensorineural hearing loss (nerve loss) have difficulty hearing the soft sounds (soft voices, whisper, conversational speech) but they do not need much (if any) amplification for loud sounds (street noise, loud talking, etc.).
Additionally, there are output limiters in hearing aids and these levels are set based on patient UCL (uncomfortable loudness levels) and the maximum output of the aid is capped.
To answer just how loud can a hearing aid get, it is possible to get a peak output as high as 138 dB SPL, but this is a peak value and represents a maximum output value which is not the same as gain, which is usually much lower, and is based on the degree of hearing loss. This type of output is available on certain models of hearing aids designed for severe to profound losses. Not all models can achieve this level.
The audiologist is responsible for the gain and output prescription of the hearing aid fitted to the patient. There are standard clinical protocols that are required, using probe mic measures, that will verify the setting of the instrument as it is seated in the ear (in situ). This is critical when fitting infants and children.
Avoid loud nose for long periods of time. Noise-induced hearing loss is 100% preventable. Turn the volume down or wear hearing protection, or increase distance between you and the noise source. 
Abraca Deborah
Audiologist
Well, maybe 99% of the time. It’s kinda tough to turn down the volume when, say, a jet crashes in your backyard.
So moved.
My friend has hearing aids and he says they shut off if the sound is too loud.
I broke my cochlear implant earpiece when I tried to hear a gunshot without protection.
By “modern” hearing aids, are you referring to digital hearing aids with filters? I got 2 of these last year and I HATE them. They’re horribly expensive and don’t work anything like the way I was told they would. For example, I was told they would amplify voices and soften background noises, and they most certainly do not do this. I much prefer the older style analogue hearing aids (which are still available) and do not have “output limiters” on them.
FWIW the audiologist told me the filters in the digital aids would “help preserve my hearing”, by toning down loud background noises, and they definitely don’t do that.
Antecdotes /= data but my best friend is deaf, so here’s his story.
When he was a child, his hearing was bad, but there, as a result of a birth defect. His audiologist told his mother to make sure he wore his hearing aids - one in each ear - 24/7 and that his hearing could probably be saved. It wouldn’t get any better, but it also wouldn’t get any worse, barring further damage. Their dogs ended up getting ahod of the hearing aids while Mike was in the bathtub, and chewed them beyond repair. Since his family didn’t have the money or insurance to get them replaced, he ended up permanently losing his hearing. He does now have a cochlear implant on one side that helps some, but it’s far worse than it would’ve been had he been able to continue using the hearing aids.
The way he explained it to me was this. By using the hearing aids when his hearing was poor, it ould train his ears to work hard to hear the sounds. (This is similar to a child who has vision trouble in one eye wearing a patch to cover the good eye to train the bad one to work harder and improve vision.) Without that extra push, his ears basically shut down.
Just my two cents. YMMV.