As you all know, I love music. I wish I loved visual art or sports more, but I don’t. I love music and with my verkakte ears, its not an easy task. I decided to review the literature and see what the research tells us about music perception in cochlear implants (CI’s).
If you look at some of the earlier research prior to 2000, you barely see much reference to music perception in CI’s. I think the researchers, and engineers were busy working on getting good speech perception. Makes sense. And as the speech perception abilities of CI users began to improve, interest began to shift to other important listening abilities such as musical perception.
One researcher who has done a lot of work in this area is Dr. Kate Gfeller. In a 2000 article (J Am Acad Audiol. 2000 Jul-Aug;11(7):390-406), Gfeller et al found that 83% of adult CI users reported diminished music enjoyment post-implantation. In fact one third of the CI users even avoided music altogether as they found it to be an aversive sound. These are not encouraging results. But do remember that these folks received their implants in the 1990’s. This technology is now 20 years old.
Looi et al, 2007 (Ear & Hearing: April 2007 – Volume 28 – Issue 2 – pp 59S-61S) did a study comparing the music perception of CI users compared to hearing aid (HA) users. Note that the HA users were all potential CI candidates, so they all had significant hearing loss. This study showed that while neither device (HA or CI) provided satisfactory music perception results, the CI users gave slightly better ratings than the HA users. So now we are actually seeing some data showing music perception getting better with a CI, but still not great.
Another study by Looi et al in 2008 (Ear & Hearing: June 2008 – Volume 29 – Issue 3 – pp 421-434) looked again at CI users and HA users who were potential CI candidates. So again these HA users also had significant hearing loss. On a rhythm recognition task, both groups did about the same. On the pitch perception task, the HA users outperformed the CI users (oh oh, not good). In fact many of the CI users needed two pitches to be at more than a quarter of an octave apart before the notes sounded any different. Not good. In western music you need to be able to hear a one semitone difference.
After reading this article, I checked what my skills were like using a CI only. I had my brother play a bunch of two note pairs on a piano keyboard. My task was to say if the two notes were the same or different and then secondly which note was higher in pitch. For the notes above middle C, I was able to reliably report if the two notes were same or different even if they were only one semi-tone apart. I was about 80-90% accurate at identifying which note was higher or lower. For notes below middle C, I needed notes to be at least one full tone apart to get the same level of accuracy, but performance deteriorated as the pitches got lower.
So here’s the thing now. Looks like I am not getting good low frequency pitch perception with the CI which is so critical for music. Low pitches may not be that important for speech as the consonants are mainly high pitched and consonants give you speech intelligibility.
I therefore personally decided to use a hearing aid in my non-implanted ear. I hear music much better whilst using a combination of a HA and a CI. But is it just me? No. A study be El Fata et al (Audiol Neurootol. 2009;14 Suppl 1:14-21. Epub 2009 Apr 22) looked at 14 adults who continued to use a hearing aid in their non-implanted ear after getting a CI. Subjects were asked to identify excerpts from 15 popular songs, which were familiar to them. The presentations were done bimodally, with the CI alone and then HA alone. Musical excerpts were presented in each condition with and then without lyrics. Those subjects who had more low frequency residual hearing (> 85 dB HL in the lows) did much better on all the tasks with both a CI and an HA than either the CI only condition or HA alone.
Another study by Gfeller et al in 2007 (Ear & Hearing: June 2007 – Volume 28 – Issue 3 – pp 412-423) also confirms the need for better low frequency hearing for music perception. In this study, CI users which electrical only stimulation (the regular type of CI) were compared to subjects with a hybrid implant. The hybrid implant uses a shorter electrode array for giving you the high pitches whilst still using a hearing aid type of air conduction for the low pitches. Usesing low frequecny acoustic hearing significantly improved pitch perception compared with elctric only CI’s. But before you go rushing off asking for a hybrid implant, you need to know that not everyone can get one of those. You need to still have sufficient low frequency hearing.
So here’s what I can conclude from these articles:
1. The newer studies seem to show better music perception in CI users than older studies. This is most likely due to improvements in technology in which the newer implants give a richer sound than the older devices.
2. Music perception with a CI via electrical stimulation could still be improved. It seems to be related to the poor perception of the low frequencies.
3. If you still have some usable residual hearing in your non-implanted ear, use a hearing aid in that ear.
4. Help your ears by making music easier to hear. Use some of the techniques I use by adding FM technology to your CI and hearing aid for either live music or with an iPod.