In the present study, mild impairment of cochlear function in patients with 
King-Kopetzky syndrome was investigated using DPOAEs. A significant decrease in 
DPOAE levels in both ears was found in patients with King-Kopetzky syndrome 
compared with the controls after considering the thresholds as a co-variable. It 
is noteworthy that the global mean levels of DPOAEs were still significantly 
greater in controls than in patients with matched thresholds. Further frequency 
analyses showed a significant decrease in DPOAE levels over the mid- and 
high-frequency range in patients with better hearing thresholds when compared 
with those in the control group. Moreover, significantly smaller DPOAEs were 
found in the ears of patients with King-Kopetzky syndrome and without SOAEs, 
than in such ears of control subjects after considering the thresholds as a 
co-variable. However, when SOAEs were present there was no difference. Decreases 
in DPOAE level appear to represent evidence of minor cochlear pathology, and 
provide a pathological basis for the difficulty of hearing speech in the 
presence of background noise, which characterizes King-Kopetzky syndrome.