A 2 khz dip in an audiogram?

My father recently showed me his audiogram (I attached the file) and he has a 2khz dip, it goes back up at 4khz and drops down again at 8khz (although not as far as the 2khz dip). This doesn’t seem to match either age-related hearing loss or noise-induced hearing loss.

Anyone have any ideas about what type of hearing loss it does match? I even checked to see if any of his medications were ototoxic, but they do not seem to be…and I don’t know if you would see this type of loss with ototoxicity anyway.

Sometimes noise induced hearing losses will occur with dips at 2 or 3KHz instead of the typical 4KHz depending on the type/pitch of the noise. Does he have a history of noise exposure. It looks like a noise induced hearing loss with a shifted dip at 2Khz insead of 4KHz to me.

The dip at 8KHz is most likely due to age-related hearing loss. Eventually the frequencies between 2 and 8KHz will most likely level out.

This may be dumb but I’ll mention it anyway> Check for a small bit of hard wax tight against the ear drum. From personal experience, a loaded tympanic membrane can under unusual conditions cause drop outs at certain frequencies.

Possibly related to this too: http://www.audiologyonline.com/askexpert/display_question.asp?question_id=293

I know its a S/n loss, not just bone conduction, but the profile is right.