native ear/s

Both are acceptable.

I agree, but prefer "ear".

You do see both.

"He has the ear of the president"

"Friends, Romans, countrymen, lend me your ears"

I like "ear" because in this sense it is a figurative, not a literal use, meaning "mind" or "understanding".

I prefer the singular as well because it makes the phrase more consistent with other "anatomical" phrases:

going on foot
invisible to the eye
lend me a hand

Thanks, fellow members, for your reply.