Sunday, November 23, 2014

Cochlear Implants, Music, and Pitch Perception

I wanted to write a bit about music perception, specifically pitch perception with my implants.  I was a classically-trained musician for quite a long time during my youth when my hearing was more-or-less normal.  My pitch perception was relatively perfect, meaning, if you gave me a Middle C, I could re-create the entire 88 pitches in my head with very high accuracy.

When I got my first implant activated and started intensive music therapy on my own, using songs I know very well, the perception was quite inaccurate.  A specific example of this was using a guitar.  I would play various notes, and for the most part it "sounded like" buzzing during the first 2-3 months. After that, pitch started to come through, but a weird thing happened with the actual perception of each pitch:  I would perceive pitches as "different" going up and down a string, but there was also the presence of another pitch.  This is best demonstrated by a picture.

So essentially, the guitar string in reality was playing the "orange" note on the far left, but what I was hearing was a distinct "red" and "yellow" note.

It has now been 8 months since activation, during which I generally listen to about 2 hours of music during my commute.  I believe I am extremely close to the orange note on the far left, if not on it.  Music with which I am intimately familiar sounds more or less like it did when my hearing loss was very mild.

But I'd like to speculate here on causality for a minute.  The high frequencies of my hearing steadily decreased from the time I was very young, until finally disappearing last year.  They have been almost completely shot for at least a decade.  Given this, I have been functionally deaf in those frequencies for a long time.

So what happens when I am suddenly able to hear across the entire spectrum again?  It's like walking from a dark room outside after a fresh snow with full sun.  It's overwhelmingly bright, and details cannot be resolved!

People with normal hearing, even if they are musicians, are generally unaware of just how many harmonics are present in even a single tone from an instrument or a voice.  Also, the timbre that gives the instrument its unique sound.  But having been deaf to most of the spectrum for 10+ years, my brain was unable to "flatten" all those layers and properly perceive it as a single tone, instead perceiving harmonics and timbre as phantom tones and buzzing, respectively.

I find all of this very interesting to think about.  I also wonder how much my previous experience as a musician has aided my rehabilitation using cochlear implants.  I hope someday to be able to leverage my experience to improve the technology and coding algorithms for future generations of implants.