1997 Volume 40 Issue 2 Pages 144-149
In recent years, much information is available concerning the relationship between EOAE and DPOAE and the differences in the nature of these emissions, but they have never been compared each other.
The differences between recordings of DPOAE and EOAE are related to factors such as the stimulus tone, recording method, and evaluation method. We presumed that these differences made comparison of the two emissions difficult.
In order to obtain simultaneous recordings of the two otoacoustic emissions and evaluate them by the same method, we developed a new procedure and assessed the effect of stimulus intensity on DPOAE and EOAE.
The subjects were 5 volunteers (10 ears) with normal hearing aged 25 to 43 years. The stimuli were two synchronized short tone bursts (f1 and f2) and their rise, decay, and plateau time duration were 1 msec. EOAE data were collected with stimuli presented at a rate of 4/sec and were averaged for 250 of stimuli. The stimulus frequencies were constant (f1=2.0 and f2=2.4kHz) and the stimulus intensity was varied over the range from 0 to 70dBnHL by 10dB increments. We investigated the EOAE and DPOAE spectra under two conditions of stimulus intensity (L1 and L2), which were 1) L1 equalled L2 and 2) L1 remained constant at 30dBnHL.
The results were as follows:
The DPOAE spectrum was found in the averaged waveform at the same time as EOAE. These spectra were recorded clearly at a stimulus intensity ranging from 30 to 40dBnHL when L1=L2 and over a range of 30 to 40dBnHL when L1=30dBnHL. The DPOAE spectrum had almost the same modality as a function of stimulus intensity as the EOAE spectrum in this study.
