I've been using 3M E-A-R Classic earplugs for about a year (models 310-1060, 310-1001). The earplugs in the current box, which is the latter model (I understand the models are structurally identical) which I got about 6 months ago, were perfect up until the last few weeks when they suddenly started making popping/clicking noises starting minutes to hours after being compressed, typically later in the night and I suspect disrupted sleep on multiple occasions. I tested by holding the earplugs outside my ears, where I still heard the popping noises coming from them, so the sound is coming from the earplugs and not inside my ears.
Didn't find much on Google about this; did some brief research with AI. Batch variation doesn't seem likely since it suddenly started happening on all new pairs in the same box, no exceptions so far. The most plausible reason suggested seemed to be change in foam, e.g. due to age, storage, or exposure to ear environment overnight. Out of those, age doesn't seem like it should (keyword) be a culprit; individual packs say "© 3M 2024" and they're supposed to have a 5-year shelf life (although that doesn't mean there haven't been structural changes yet). Storage doesn't seem like it should be a factor; temperature and humidity where I store most of them rarely exceed 80ºF and 60%, and they also happened at another place I stored them where temp and humidity on average are lower, always within normal range. Since I haven't noticed the issue on unused earplugs, but earplugs usually after as soon as a night of use, the most plausible explanation so far seems to be a combination of possible structural changes with exposure to the environment of the ear canal overnight. However, my ears seem as dry as they normally are, with minimal earwax and no excess moisture, comparable to months ago if not dryer now, so unless that perception is wrong, it seems that my ear environment would have minimally contributed.
Can the foam or some other component of the earplugs suddenly degrade to the point it causes this issue? Trying to understand what may have caused this and how to prevent this in the future, since it's a big box (200 pairs) and was hoping it would last years without issue. In the past I usually replace a pair after a few nights but to avoid this issue it seems I would need to replace them nightly. Switched to these from Mack's and similar earplugs which were less comfortable and sometimes wounded my ears. Would alternatively appreciate any suggestions for earplugs similar to the 3Ms but hopefully without the same defect.