Auditory recruitment is a condition in which certain defective ears are more sensitive to changes in intensity of sound than are normal ears. This characteristic usually manifests itself in at least two ways. One feature of it is a sudden detection and distinct awareness of the threshold of sound in an ear with recruitment as compared with a gradual and uncertain onset of threshold in a normal ear. Another manifestation is that at succeeding levels above threshold the difference in loudness for a tone of given intensity between an ear with recruitment and a normal ear tends to diminish and disappear. For example, a tone of 40 to 50 db. above threshold in an ear with recruitment might seem as loud as the same tone at 100 db. above threshold in a normal ear. In recent years the detection and measurement of auditory recruitment has become an important aspect of