Sound Quality Question

Hi. I received this comment and question on my weekly post so I thought I would provide the most detailed response I can in a separate post.

I am single sided deaf in left ear with very minimal residual hearing on high frequencies. About implant, I still can’t decide if I should go for external CI like Med El or wait for Acclaim to be commercially available. It’s the natural sound quality Med El boasts bs the discreteness of Acclaim. So, can you please throw some light on what’s the overall sound quality both for speech and music? Is it very robotic and only in high frequencies or you can hear a lot lows and basses?

The Short Answer

It is too early in my days as a CIborg (implant recipient) for me to be able to provide a useful answer because the sound quality changes and I have only had my implant turned on for a little over 3 weeks at this point. I believe that, ultimately, once my brain has learned to accommodate the implant, that the sound quality I experience will be at least as good as any other implant, or better, and the reasons I believe so are in the long text below. In reality, even with the way it currently sounds, I’m ecstatic. It is such a vast improvement over what I’ve had for at least a decade, and the convenience is such that I feel like I’ve gone back to non-hearing-aid wearing hearing. OK, I have to recharge the battery every 3 days while I have a morning coffee and read the news for whatever disaster has befallen the world overnight. Compared to having a device attached / hanging off my body somewhere, I’ll take the inconvenience of having to charge the battery every three days and, if I want to get moving, I can just use the harness for the charging induction coils and carry on a normal day.

How Implants Work / The Technology

I am not very familiar with the MedEl device so I cannot answer that directly, nor am I a cochlear engineer so my answer here is based on my research and experience over the past 10 years or so\ and may not be 100% accurate.

When I first starting looking into cochlear implants I was living very close to Advanced Bionics HQ in Santa Clarita, CA. Naturally, I went to a presentation they did, met and spoke to their evangelists and some clients / patients.

It is my understanding that the AB implant has 32 probes which, and this is an assumption, I assume are also referred to by some as electrodes. The AB implant is a “traditional” implant and that means that the electrodes and transducer are under the skin but everything else, battery, processor and microphones are external.

The MedEl device is also a “traditional” device but I have not looked to see how many electrodes it has.

The Envoy Acclaim, from my understanding, has 19 electrodes, also placed, and glued, into the cochlear, like all traditional implants.

I know that all implants require a “retraining of the brain”. I know this for certain due to what I have read and from my research of AB and the Envoy Acclaim. This need apparently arises from the fact that, not only is the implant replacing thousand of stereocilia (hairs) with, in the case of the Acclaim, 19 electrodes or, in the case of the AB device, 32 electrodes, but they are also not placed in a specific location relative to where the brain was previously receiving signals.

This necessitates retraining the brain to recognize the new signals it is receiving, from the wrong location in the cochlear, accurately. Imagine that suddenly the electrodes producing bass signals in the cochlear are producing them in an area from which the brain is used to receiving, say high frequencies, or very high frequencies – like 8k or 15k ? Well, it’s going to think, at least initially, that it’s hearing high signals, not bass.

So the brain has to be retrained. Imagine if the piano keyboard, or your computer keyboard, was suddenly shuffled and everything was misplaced. You’re just not going to be as efficient with that new keyboard for quite a while. That’s why we are stuck with the computer keyboard, for example, and other keyboard layouts have not succeeded.

In the meantime, while your brain is trying to figure out what signals it is receiving, the sound is perceived incorrectly.

So, presently, I have Donald Duck talking to me in my implant ear and, James Earl Jones speaking to me in my hearing aid ear (almost). I am receiving most of the bass I hear in my left ear and pretty much any frequency over about 3K in my right, implanted ear. Fortunately for me, my brain combines them into a single audio input unless I really listen intently to my right ear, which is what I do when I am trying to retrain my brain rather than just communicate.

My sense, therefore, considering the above and assuming I am largely accurate, even the MedEl device is going to sound metallic, or like Donald Duck or Tweety Bird until a persons brain has re-calibrated itself to recognize the sound it is receiving from the implant. Just like all the others.

Natural Sound Quality

As for “natural sound quality”, all of the devices are digitizing the sound in order to produce the very small electrical signals in the brain. Digitizing changes the quality of the sound from the natural by it’s very nature. Everything in the chain, from microphone design and location, to the wire used to connect the micrphone(s) to teh processor, to the processor, firmware (software in the processor), electrode design and placement in the cochlear, number of electrodes and the audio bands they replicate / produce, everything effects the quality of the perceived sound.

One of Envoy’s goals was to use design a device that used as much of the person natural hearing as possible. So they don’t use a “micrphone” in the sense that the traditional implant manufacturers do, and their sound sensor is behind the tympanic membrane, where the sound is originally transformed into movement in the inner ear bones to move the stereocilia to produce electrical impulses to the brain. In this way, the Acclaim uses the individuals natural ear shape and auditory canal which shapes the sound on it’s way to the ear drum. It then uses the ear drum to further shape the sound. The expectation, and hope, then is that using this natural path to the sensor is going to be more accurate for the user than simply placing a microphone above the ear, in the wrong place for what the brain is used to, and / or behind the ear. However, in practice it may not work out that way because the external microphones may be compensated in software, to a large degree, and the internal sensor that Envoy uses may not actually be as good as one, or two, external microphones even if they are in an unnatural location.

Lots of things can be “tweaked” in the firmware, but only the listener really knows what it sounds like relative to what it used to sound like, so “natural” is going to be different for a lot of people.

This may sometimes take tweaks in the implant firmware too. I’m not 100% sure, but I have heard it said that people who are musicians, or listen to a lot of music, do better than those that don’t.

On A Personal Note

My hearing has been deteriorating since I was in my 20s. The deterioration seems to have accelerated over the past 20 years.

I first knew for sure I had a problem when I went to see an otolaryngologist (ENT) in my early 30s because I had ringing in my ears (tinnitus). He checked and said the good news is that I wasn’t going to go deaf.

Well, the noise became a lot worse over the years but I have always been one that has been able to ignore it but, and you will know this if you’ve had hearing tests, the tinnitus interferes with tone recognition.

It is my understanding now, and I believe this to be true but there are disagreements among the professionals, that tinnitus is caused by the brain (nerve ends) generating its own noise. This means that none of those supposed tinnitus “remedies” are likely to work, at least not the chemical ones, only the remedies that help you ignore the tinnitus or drown it out.

I have been told by a number of people to not expect the implant to cure the tinnitus. This is quite possibly true, but I can tell you without doubt, my tinnitus in my head is half what it was before I had the implant. In fact, I cannot hear any of the high pitched ringing I used to hear in my right ear at all while I can still “hear” it on my left side. I am ecstatic.

Summary

I hope this helps anyone who reads it but I do recommend you discuss this more with your own doctors. They have been trained to know what they are talking about.