Here is a portion of the 500 Hz data.  To help separate out the appearance of the rarefaction and condensation elicited responses, I put a yellow highlight under one of the waves.  (If you click on the image, you can see it in large scale.)

Do you see how V is delayed by about the same period as the stimulus?  And if you look at the “yellow” wave, if we tentatively mark III and I, we have a problem – there is an extra wave even earlier.  So, we are likely seeing the stimulus artifact and the physiologic response merging.  When summated, all we see is wave V, but that doesn’t prove that the other waves WERE artifact, it only says that they were out of phase by 1 ms from each other!  Fortunately the trough that follows V is broad and large and “slower”, so it doesn’t cancel.  We may not be able to tell exactly which wave is what, but we can see an evoked response. The problem is when you don’t see a clear V. Then you are left wondering if you are seeing a combination of stimulus artifact and/or ringing cochlear microphonic.

To get rid of the physiologic response, you can gently take the tube off the insert earphone. What remains in your trace is then stimulus artifact, not cochlear microphonic and not ABR (since the sound didn’t reach the ear to be heard).  Unfortunately I don’t have that to show you.

Now that we’ve seen why the responses are ugly, let’s move on to interpreting the threshold of the evoked response.  Next page please!