This compaction of dynamic range leads to recruitment, an abnormal growth in loudness as sound intensity increases. What sounds normal for someone with normal hearing may be too soft for someone with recruitment, and what is too loud for someone with normal hearing is also too loud for the patient with recruitment. In effect, the range of sound intensity that a patient with recruitment can tolerate is much narrower. Further adding to the difficulty, recruitment is observed in those frequencies that are most impaired—in the high frequencies, which also carry critical information for speech understanding.
