What is another word for "surd"?

Roget's Thesaurus (1911) lists these synonyms for "surd": adder, beetle, close, deaf, deaf-mute, deafen, deafness, dull, ear, earless, evil, hard, hardness, have, hear, hearing, inaudibility, inaudible, out, post, render, shut, stone, stop, stun, surdity, turn.