Bilateral / Unilateral

Bilateral means hearing loss in both ears. Unilateral means hearing loss in one ear, with normal hearing sensitvity in the other ear.

For example, the audiogram on the left depicts a bilateral hearing loss, whereas the audiogram on the right depicts a unilateral hearing loss. 

Symmetrical / Asymmetrical

Symmetrical means the degree and configuration of hearing loss are the same in each ear. Asymmetrical means the degree and configuration of hearing loss are different between ears.

For example, the audiogram on the left depicts a symmetrical hearing loss and the audiogram on the right depicts an assymetrical hearing loss.

Progressive Hearing Loss / Sudden Hearing Loss

Progressive refers to a hearing loss that becomes worse over time. Sudden refers to a hearing loss that occurs quickly; such a hearing loss requires immediate medical attention to determine its cause and treatment.

Fluctuating Hearing Loss / Stable Hearing Loss

Fluctuating means hearing loss that changes over time—sometimes getting better, sometimes getting worse.  Stable hearing loss does not change over time; it remains the same.