I'd imagine it might be getting a little bit gummed up which is reducing the sound. Have you tried taking it apart and cleaning it?
I wasn't aware these were user serviceable like the White Industries ones?
I've tried cleaning best I can but probably does need to come off for a deep clean
@Maxice started
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I'd imagine it might be getting a little bit gummed up which is reducing the sound. Have you tried taking it apart and cleaning it?