In acoustic distortion products (ADP) recording, bitonal acoustic stimulation is applied (simultaneous sending of two pure tones).
These two primary stimuli, with repective f1 and f2 frequencies, will generate a human physiological characteristic distortion product at frequency of 2f1-f2.
On healthy subjects as for subjects with endolymphatic hydrops, a postural test (transition form standing up to lying down) causes an increase of intra-cochlear pressure (exaggerated in the context of Menière’s disease).