不常用的一個後綴，比較生僻，來源於希臘語。

[Greek akoustikos, from akouein, to hear.]

The most common example here is hyperacusis (Greek huper, over, beyond), abnormally acute hearing or painful sensitivity to sounds. Others are paracusis (Greek para, amiss or irregular), a general term for an abnormality of hearing; hypoacusis (Greek hupo, under), a reduced sensitivity to sounds; and diplacusis (Greek diplous, double), a defect of the inner ear so that one sound is heard as two.