Yesterday I learned what's causing the ticking sound that sometimes occurs in meditation and that coarises with subtler and more effortless breathing: sudden and brief outlets of air through the ears, as if a hatch opens up and closes, which creates a vacuum that makes air come in through the nose automatically. The reason I noticed this was bathtub meditation with ears under water (bubbles!).

I thought maybe someone else might find this interesting, unless you all already knew this.