User blog comment:Xilinoc/Ch. 561 - THE VILLAN/@comment-28861328-20131211160420/@comment-1268838-20131211195643

You can still hear, yes, but even a small rupture can impair your ability to do so. Going so far as to destroy them completely won't exactly render you deaf, but it would certainly damage your hearing. Or at least, your ability to appreciate music, which seems to be the point of Rose's Bankai. Compare to other series, where characters sometimes tear off their outer ears to avoid sound-based abilities.

Of course, Kubo is the guy who puts the heart in the left side of the chest, so I'm not exactly praising his knowledge of anatomy or anything.