Contralateral suppression of DPOAE measured in real time.

The aim of this study was to measure contralateral suppression of distortion product otoacoustic emissions (DPOAE) in real time. A total of 10 human subjects were studied with a novel device to record DPOAE without signal time averaging, using digital narrow band pass filtering. Real time DPOAE levels were recorded at 2f1-f2 using primary tone settings of f2/f1 = 1.22 and L1 = 70 dB SPL, L2 = 65 dB SPL, at five values of f2 between 2.2 and 7.7 kHz. An acoustic stimulus was applied intermittently to the contralateral ear to cause DPOAE suppression. Characteristic features of contralateral suppression were identified and distinguished from small spontaneous variations in the real time DPOAE signal. Magnitude of suppression increased with contralateral stimulus intensity. Onset latency of suppression was around 43 ms (31-95 ms). Potential clinical applications are discussed in the light of these findings, including a role in improving the specificity of neonatal hearing screening.