Friday, April 3, 2009

Cochlear implants vs. hearing aids. The math behind this!

Deciding if you should "upgrade" your HAs to CI(s)? My math will give you the odds and perspective and make it easier for you to decide. Do note that there is a risk associated with the surgery required for CI, as well as losing most or all your natural residual hearing. There is also a $50,000 cost that you and/or your insurance must pay.

I will do the math for my unaided/aided audiogram. Note that an average CI result is 40db from 250Hz to 8000Hz. If you are hearing 25db threshold, consider yourself lucky! Looking at my unaided red points on audiogram, some of you might think CI would benefit me. But thanks to today's HA technology, I could be aided up to the blue points on my audiogram.

It used to be standard photocol that a CI candidate had to try at least two brands of the best HAs set to max gains for at least 90 days each brand before he got approval for CI. It also used to be that you needed to be profoundly deaf, now I am seeing moderately HOH people somehow being approved by the surgeon and even insurance for CI!

CI used to be taken seriously and only as a last resort for the profoundly deaf with so little(or no) residual hearing that no HA in the world would be much, if any good. Now there's way too much hype and pressure to force or persuade as many people as possible to "upgrade" to CI.  I am not part of any deaf groups but still agree with much of the controversity surrounding CIs as trying to "fix" deaf people, especially when HAs are giving them decent benefit.

Ive read several CI blogs and it's a recent phenomenon that they are approving CI on the moderately HOH. All the older blogs, they had profound HL for the most part with a few in the very severe(near profound) range in the low frequencies sloping well into profound in the high frequencies. They would have a 75db to 90db HL at 250Hz sloping down to 110db to 120db HL at 1000Hz. Most of them had 120db or NR at 2000Hz and above. In short, their hearing was often worse than even mine.


Speech comphrension seems to be overhyped as the only thing that matters but environmental sounds and music is equally important. Anyone considering CI should not have to trade away a range of their hearing for another range. It's like trading ten(10) dimes for four(4) quarters. Different units of value that both add to the same dollar amount. I will first do the math for speech comphrension then for environmental sounds then finally for music.

A man's voice has a 125Hz fundamental frequency and ranges from 100Hz to 1000Hz. My best aided scores should be 5db at 125Hz, 10db at 250Hz, 20db at 500Hz, 30db at 750Hz and 30db at 1000Hz.  5+10+20+30+30=95/5=19. CIs probably give better quality aided hearing so ill add 5db to the CI score and come up with 24db for CI to equal my 19db for HAs regarding speech comphrension for male voices.

A woman's voice has a 250Hz fundamental frequency and ranges from 300Hz to 3000Hz. My best aided scores should be 10db at 250Hz, 20db at 500Hz, 30db at 750Hz, 30db at 1000Hz, 40db at 1500Hz and 50db at 2000Hz.  10+20+30+30+40+50=180/6=30. CIs probably give better quality aided hearing so ill add 5db to the CI score and come up with 35db for CI to equal my 30db for HAs regarding speech comphrension for female voices.

A young child's voice has a 500Hz fundamental frequency and ranges from 450Hz to 4500Hz. My best aided scores should be 20db at 500Hz, 30db at 750Hz, 30db at 1000Hz, 40db at 1500Hz and 50db at 2000Hz. NR at 3000Hz and 4000Hz so ill put 65db as a finite number that resides just outside the speech banana. 20+30+30+40+50+65+65=300/7=43. CIs probably give better quality aided hearing so ill add 5db to the CI score and come up with 48db for CI to equal my 43db for HAs regarding speech comphrension for children voices.

The conclusion is I will be understanding speech from males at a barely normal hearing level but still better than most CI wearers. Ill understand speech from females better than a little more than half the CI wearers. Most CI wearers will understand speech from children better than me.


Now ill do the math for environmental sounds. I am breaking them down into five frequency ranges: very low, low, mids, highs, very high. Like speech, the sound banana(better known as sound spectrum) would be similar. However, the greatest percentage of sound will be lower frequencies. The decibals in the sound spectrum would range from 20db to 70db. The speech banana generally ranges from 30db to 60db in comparsion.

The very low frequency sounds are at 125Hz and below. My unaided hearing loss is moderate at this frequency range. No audiometer tests below 125Hz(and some don't test below 250Hz), however I should be hearing at normal ranges when aided, especially considering I could be hearing aided as good as 5db at 125Hz. Many CI wearers don't hear below 125Hz and some don't even hear below 250Hz. I know a bunch of CI wearers who miss being able to hear and enjoy bass music.

The low frequency sounds are at 125Hz to 500Hz. My best aided scores should be 5db at 125Hz, 10db at 250Hz and 20db at 500Hz. 5+10+20=35/3=12. I round to the nearest whole number. The CI score would be about the same, maybe 1db better than HAs for environmental sounds. It's highly unlikley today's CI technology will come close to my HA aided scores in low frequencies and even more so in very low frequencies. 75% of environmental sounds are 500Hz and below.

The mid frequency sounds are at 500Hz to 2000Hz. My best aided scores should be 20db at 500Hz, 30db at 750Hz, 30db at 1000Hz, 40db at 1500Hz and 50db at 2000Hz. 20+30+30+40+50=170/5=34. The CI score would be about the same, maybe 1db better than HAs for environmental sounds. It's possible today's CI technology will come close to my HA aided scores in mid frequencies. 20% of environmental sounds are 500Hz to 2000Hz.

The high frequency sounds are at 2000Hz to 8000Hz. I don't even need to do the math to know my HL is infinite in the high frequencies. I have a tone generator where I can test my hearing using my computer speakers. I can hear 2000Hz but it's faint. On a good day I can hear up to 2500Hz at threshold levels regardless of how high my speaker volume is at. The problem is I may have less than 1db dynamic range at 2500Hz, by the time I hear this tone, I have already reached the SPL on my HAs. However I am not missing much as only 5% of environmental sounds are 2000Hz and above. This includes very high frequencies at 8000Hz and above.

The conclusion is I will very likley hear low and very low frequencies worse with CI. This means id be missing much of the huge 75% range. I would hear mid frequency sounds better than a little more than half the CI wearers. The mids account for another 20% range. Most CI wearers will hear high and very high frequencies better than me, they would enjoy that 5% range that I am missing pretty much entirely.


Now on to music math. I will break it down into octives and intervals between octives.

I can hear the lowest piano key with my HAs. That's 27.5Hz. One octive above is 55Hz. Then 110Hz, 220Hz, 440Hz, 880Hz, 1760Hz. A quarter octive above that is 2200Hz. So I hear up to 6.25 octives. However I hear 6 octives easily. With CI, the average result is 250Hz to 8000Hz which is 5 octives. Some CI wearers may have their electrodes inserted deeply enough to properly hear down to 125Hz so they'd still hear the same 6 octives I hear easily. A normal hearing ear's cochlea can hear as low as 16Hz to 20Hz and as high as 16KHz to 20KHz. This is 9.6 to 10.2 octives. I hear about 60% the number of octives which honestly isn't bad for a profoundly deaf person.

The CI would then simply be shifting the same 6 octive range a little more than 2 octives higher than what I hear. My range is 27.5Hz to 1760Hz, a CI's range is 125Hz to 8000Hz. Like environmental sounds, most music is in the low frequency range, although more than 20% of music is in the mid frequencies and more than 5% of music is in the high frequencies. I don't yet know the exact percentages.

The real problem is today's CI has up to 22 electrodes and many people are still getting only 8, 12 or 16 electrodes. A normal hearing person can distinguish as many as 20 different puretones between each octive. I can still distinguish 10 different puretones between each octive. CI wearers may be able to distinguish only 3 different puretones between each octive. It's a limitation of so few electrodes. 16 electrodes means you will only hear 16 different puretones. You really need at least 100 electrodes for music to sound like it does to a normal ear and cochlea. If music is important to you, wait for the 128 electrode CI comming in the near future. It will also help in other avenues besides music.

Today's CI wearers complain how bad music sounds and also that they can't hear bass music(just feel the vibrations) even profoundly deaf people appear to hear and enjoy music more than CI wearers. Music can easily be loud enough for me to hear unaided!


The conclusion is that certainly no one who's moderately hard of hearing will benefit from today's CI technology and probably not ever from any of tomorrow's CI technology for the matter. They would be able to be aided to normal hearing without even comming close to maxing out the gains or needing the best HAs.

The severely "deaf" also is unlikley to benefit from today's CI technology, well unless they get extremely lucky and hear down to 15db aided with CI. They still would lose out on music and environmental sounds and possibly speech comphrension with male voices for the matter. Some of them may still be "candidates" due to unusually lax requirements by surgeons and even insurance companies. Unless all that matters is hearing/understanding your children and wife a little better without lip reading, stick with HAs.

The profoundly deaf accounts for only 0.1% of the population and the worst 1% of the hearing impaired, but that group is the most likley to benefit from CI. As bad as my hearing is, the math I have done above shows I would trade off alot of aspects to hearing in exchange for understanding speech better when listening to children and maybe women as well. Thus I will wait for better CI technology and gradually lose more hearing.

For those of you deciding if you should "upgrade" your HAs to CI, please carefully read the above and plug in your own audiogram into my math numbers. I provided my own example and I can help you by doing the math for you. I can't decide for you, only your insurance(if any) your surgeon and you can decide for you. Do not let anyone pressure you into a CI, alot of people have a monetary reason for doing so. I can give you the numbers, the odds and realistic expectations. The worse your hearing is, the better odds you will have, it's that simple.


  1. Where do you get the idea that 40 db is normal??? This basic idea is the flaw in all of your theories!!!!!!!!!!!

  2. You are wrong about "severe" as well. ALL the research shows that people with severe losses do better with CI's as well. That is why the FDA has expanded the criteria! It is as high as 40 db in the low frequencies because they perform better with CI's! This whole blog is full of unthruths and false statements!

    You are just writing this to convince yourself that you are right!

  3. I'd really like to see professional resources to any research you might have done to back up your theories. I'd also like to ask why you are so fascinated with this one subject... your entire blog is about why your HAs are so much better than a CI in your opinion. Why the fascination with that one single minded train of thought? Personally, I get the idea already... It's called beating a dead horse... you've made your point. Do you plan to discuss anything else at all in your blog? (like who you are... your experiences in life as a deaf person... family... anything???) I'd be interested in reading about you and your life. I'm not really interested in reading more of the same you've already posted repeatedly. I'm sure there's a whole lot more about you to share than this one thing.

  4. Michelle, amazing that you only lost half your hearing in the implanted ear. Have you Googled hybrid CI? I might go that route when/if I end up needing a CI. It's like the best of both worlds, you still wear a HA and hear from it but also get the benefits from a CI :)

    As to your reply in my blog, I got the research from Google, case studies, reading other blogs and talking to other CI wearers. HAs for most people are better than CI, it's those who are so profoundly deaf that there's not enough residual hearing to amplify that they have no choice but go CI if they want to hear more. My blog is about my hearing loss, HAs and CI. I will be happy to chat on instant messenger with you about my life, hobbies and other interests. Thanks for your reply.

    Miss Kat's Parents, If you read further down on my blog, I have provided pictures of CI audiograms and you will notice it's on the 40db line. Some people get down to 30db for some of the frequencies. I have read other CI blogs and the surgeons all say to expect 40db as being realistic but that some people can do better than this. 40db is still great if you have no measurable residual hearing. But for others who are already hearing better than 40db with HAs, stick with HAs.

    No one in their right mind would trade 40db unaided hearing for 40db aided hearing. Even my friend who has a CI thinks it's crazy! I guess it might make a little sense if a person hears 40db at 250Hz, 80db at 500Hz and NR at 1000Hz and above. That person would be far better off with a hybrid CI/HA design and get the best of both worlds, of course it depends on how lucky you get with hearing preservation. I am providing a source:

  5. You are an idiot deaf dude or the so called Hybrid. Not in the deaf and not in the hearing world. In your entire profile, you have yet to mention the specifications of your aids. WHY ARE THEY SO MUCH BETTER for you. Get your vocabulary correct DEAF DUDE. It is Octave not OCTIVE. Like the other gentleman said, you are the only idiot who thinks 40 dB is better. You complete moron, the blue X---X is the response from your left ear. The line marked as CI-CI---CI is your cochlear implant audiogram. The A---A audiogram is complete bullshit. A hearing aid amplifying so much in the low frequencies.... and you love it.... you don't hear all the background noise when you are in a bar... 28 year old geek.