O/T medical mystery - hearing same tone different in each ear

this one kind of freaked me out yesterday.

i put a tuning fork up to my right ear and i get one tone. i put the same fork up to my left ear and get a lower tone. these two tones are one and a half steps(three frets) apart on the guitar. i can hit the tone i hear with my voice and grace said that yes, they are different notes. the tone i hear in my left ear matches the tone grace hears, both from the fork and from my voice when i match what i hear with the left.

what is this?