Calamus

The calamus is an aquatic plant similar to water lilies that grows in warm, humid climates on the surface of waters such as lakes or ponds. Its maceration, which among other ingredients includes several small insects, is a sought-after preparation because it helps to recover hearing.
A creature who temporarily suffers the deafened condition immediately recovers their hearing. In addition, a creature permanently deaf for natural reasons has a 50% chance of recovering hearing equivalent to approximately 25% of normal hearing for 1 hour.