Please consider removing aria hidden and remove aria title. You can't have hidden because you have labelled by and you don't need a title AND a labelled by. This is present in <i class="icon fa wp-bell fa-fw " title="Toggle notifications menu" aria-label="Toggle notifications menu" aria-hidden="true"></i> Since there is no exposed text, the user must perceive the icon. Remove the aria-hidden, please, and the title is 'extra' but ok since aria-label will be the hierarchical preference. 

This is per an accessibility audit performed by a client. I have verified this appears to be present in 4.1, as well. Audit was on 3.11.