Prior to having a hearing test I decided to do one myself so that I could, out of curiosity, compare my results with the professional one.
The first two photographs show my set-up; an oscillator, an attenuator and a pair of 'phones.
The second two pictures are of my results.
Since I had no way of calibrating the 'phones, I determined what frequency I found to be loudest, it turned out to be 1kHz, in my best ear at a comfortable, but fairly high, volume and used that signal level as the reference (0dB)
I carried out the test several times and found that the curves were very similar, with my right ear being 10dB down with reference to my left. It was satisfying to discover that, except for the reference levels, my curves and that of the professional were, for all intents and purposes, identical.