Hi,
This is what I have found with the Apple earpods specifically. I've had two pairs and both have stopped working properly over time. Both pairs have had the volume in the left side go quiet. It appears like the large opening has very low or muffled sound but the smaller grille on the side of the earpods has sound coming out.
I use my earpods a lot at night in bed, often falling asleep with them in. This results in a warming of the wax in the ears and a thin almost imperceptible film, builds up on the grille, effectively muting the sound. I was very sceptical that this was causing the issue as my earpods looked very clean, even on extremely close inspection.
I have found this procedure works best if you wear the earpods for a while, to warm up the wax film and then remove them from your ears and brush the main grille repeatedly with firm but gentle pressure using a toothbrush ( I used an old one, but if you love the flavour of earwax, feel free to use your current one! ). You're not trying to force the bristles through the grille, just to brush the wax off. You should find that 'bits' will form on the grille itself and then they will be brushed off.
You will be surprised how much difference a small amount of wax removal will make.
Hope this helps!
S
