David Liu a professor at Harvard University led a work where using CRISPR-Cas9 they alter a faulty gene associated with a form of inherited, progressive hearing loss in the tiny ears of newborn mice. Using the breakthrough technology of CRISPR-Cas9 there were able to edit the gene sequence and replace the mutation with the correct DNA sequence. As a consequence, the mice recover the capability to hear again, reducing the deafness.
In general, genetic mutations are responsible for 50% of all cases of deafness, and in particular, the same mutation they were able to correct in mice, also cause hearing loss in humans. So on, they are expecting the same approach could be use in humans in near future.
The scientific work was recently published in the prestigious journal Nature. You can find the whole scientific manuscript in the next link, although if you are not in a university or research centre subscribe to the journal it will ask you to pay for it.