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Just so I have this straight, I believe you're asking if a damaging, loud noise will still be damaging if it has already caused the damage on the hearing hair cells.

Two things factor into permanent hearing loss from noise: volume and time sustained. As long as there are hair cells left to damage (partial hearing loss), using the same original volume and amount of time will also damage additional cells. So raising the volume above a safe level will continue to damage your hearing whether you can hear it well or not.

The CDC recommends that people with hearing loss keep the volume down to a safe level even with hearing loss and recommends techniques like reading lips for help if it's a person speaking. This will help prevent it from getting worse. https://www.cdc.gov/nceh/hearing_loss/what_if_i_already_have_hearing_loss.html

Thanks, i was indeed thinking about hair cells! I have to admit that the exact mechanism underlying hair cell damage is still somewhat elusive to me^^

Thanks for sharing your experience!

Another CDC page uses an analogy of grass being like your hair cells. If you walk over grass and bend the grass (listening to a loud concert) they'll return to normal after a short while. But if many people walk over the grass, it will die.

Also, besides the hair cells, loud sound can also damage the auditory nerve.

https://www.cdc.gov/nceh/hearing_loss/how_does_loud_noise_cause_hearing_loss.html#:~:text=Listening%20to%20loud%20noise%20for,neural%20system%20is%20generally%20permanent.

I can't find any specific experiments that address your question directly. But I can present some evidence on related topics.

First, let's look at age-related hearing loss (ARHL), otherwise known as presbycusis. It is, as you might guess, hearing loss that is associated with aging and no other specific cause (i.e. no previously known noise-induced hearing loss (NIHL)). ARHL is complex and likely has many causes. But one hypothesis (of many) is that ARHL is often an accumulation of a lifetime of noise exposures, leading to a hearing loss in old age (Van Eyken et al., 2007).

This leads us to the concept of hidden hearing loss, which occurs when neurological or cellular damage occurs after intense noise exposures, but does not register a permanent hearing loss on typical audiometric tests. This is thought to especially occur after noise exposures that cause a temporary threshold shift (TTS), which you may have experienced after a loud concert (Kujawa & Liberman, 2009). Furthermore, exposure to damaging noise at a young age increases the likelihood and severity of age-related hearing loss (Kujawa & Liberman, 2006).

Taken together, this shows that exposures to damaging noise increases your susceptibility to hearing loss as you age.

But, you might ask, what about sound conditioning and toughening? These paradigms are both used to try and use noise exposures to protect against future noise exposures. However, sound conditioning is the use of low-level, non-damaging noise, either continuously or intermittently, to protect again future acoustic trauma (very intense noise exposure). Toughening is the use of an intermittent noise that causes a TTS. The degree of TTS is often reduced after repeated exposures, sometimes eventually resulting in no measurable TTS at all (Niu & Canlon, 2002).

Recall that there is evidence to suggest that incurring a TTS may cause an increase in susceptibility to NIHL or ARHL, so you may not want to try toughening your cochlea. Sound conditioning, on the other hand, may be a promising way to reduce susceptibility to additional noise exposures, however, it has primarily been tested as a protective method against acoustic trauma, specifically (Harrison et al., 2021).

With this information about cochlear pre-conditioning, there is some evidence to suggest that certain noise exposures can have a protective effect.

Finally, circling back to your original point, the selection of an appropriate noise exposure paradigm for sound conditioning is essential. Choosing too intense a noise exposure as a pre-conditioning agent, is associated with an increased hearing loss after acoustic trauma (Fowler et al., 1995).

So in conclusion, based on the above information, it would be my hypothesis, that someone with hearing loss, is equally susceptible or more susceptible to subsequent hearing losses, compared to someone with normal hearing. Note that, again, I do not have any specific evidence for your exact question.

There is evidence that consuming antioxidants such as those in chocolate before or slightly after hearing something above safe thresholds can help prevent hearing loss. It supports the theory that damage to the hair cells of the ear are at least partially from oxidative stress.

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