One of your questions asks about mosquitoes, so "human ear" would be inappropriate. In the other question claims to be about animals in general, but uses humans as an example. It doesn't seem like "human ear" would be appropriate for either of these questions.
In general, we have human-anatomy and sensation tags, I think asking for every human body part to have its own tag is a bit overkill. I also agree that sound belongs in physics, but if it were introduced here I'd favor that it be called something like sensation-hearing so as to make the superset clear.
I agree with the tag human-ear.
It is in line with StackOverflow's current guideline about tags.
They are for instance migrating more tags to [category]-[subcategory] like
I agree with Shep that sound is more to Physics. It should be sound-organ or sound-sensation or something similar. What is important is that you write a good wiki page about the tag that the user knows the tag really means in my opinion.