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Clinical Definition:

• Normal human hearing sounds: 20 - 20,000 Hz
• Hearing Test (Audiologist) Pure Tone < 25 db </aside>

1. Definition: lowest level (in dB) where the patient can hear something 50% of the time
   1. Below 25 db = Hearing Loss (<25 db)
   2. AC > BC (air-bone gap, 20 db +) = CHL
   3. AC = BC (no air-bone gap) = SNHL
      • loss 4000 Hz = Noice-indcued SNJL
      • loss higher Hz = old dage
      • Unilateral lower Hz = Ménière’s Disease (Labyrinthitis)

CHL

SNHL