Your Audiology Tutorial: Recruitment

The term "recruitment" in the world of audiology refers to a rapid growth of loudness at a pitch (or pitches) where hearing loss occurs.  You may recall the cilia or hair cells that line the cochlea (snail shell organ in the inner ear).  Each are coded for different pitches.  Damage occurs to them due to aging, noise exposure, or otoxicity (among other reasons).  When a sound enters the ear at a certain decibel level, the adjacent hair cells that are undamaged (normal) are "recruited" by the damaged ones to create the perception of sound much louder than it actually is.

Someone with recruitment may not hear you speaking, but if you raise your voice even a bit it may be uncomfortably loud for them.  Thus, the range between what is barely heard and what is painful may be narrow.   Programming hearing aids for these patients can be challenging, requiring the use of compression to assist in severe cases.