Marne, the name he is given in the novelisation
Talk about it here.
Marne was a Mentor and a medical officer on Thoros-Beta. He was charged with assessing the health of Lord Kiv's captives. He had unusually sensitive hearing and found the everyday sounds of underground living distressing. (PROSE: Mindwarp)
In 2379, the Sixth Doctor freed Yrcanos from his cell. Marne attempted to contact Crozier for confirmation, after which Yrcanos's shouting was enough to enable him and the Doctor to escape. (TV: Mindwarp) He did not sound an alarm, not wanting to subject himself to the sound. (PROSE: Mindwarp)