Longtime UK hearing aid user Karen Stockton passionately describes in The Limping Chicken how what looks good on paper, namely that of “enhancing” audibility of sounds with the wide dynamic range compression (WDRC; technically logarithmic gain) found on digital hearing aids, does not work for the profoundly deaf whose broken ears have cochlear dead zones as they rely on speech envelope detection, namely those whose auditory system between their outer hair cells and dorsal cochlear nuclei lack the temporal resolution to resolve the fine structure of speech. The reason: WDRC actually “squashes” the speech envelope, destroying the ability for the auditory cortex to decode that crucial information transmitted from the cochlear nuclei; and when this information is lost, as will be explained below, disastrous results can and will occur.
When you read Karen’s story, you’ll note the condescension, bordering on arrogance, of her audiologists, with their “we know what’s best for you” attitudes. What’s more, we’ve seen these attitudes festering on both sides of the Atlantic, as improperly trained, button-pushing hearing aid professionals are just “chimping it” by plugging the audiogram into the fitting software, clicking Autofit… And then ignoring the patient complaints, because they don’t understand the fundamentals of speech signal synthesis and detection. This is the second article in our series on speech envelope preservation, the first being Speech Envelope Detection vs AGC Attack & Release in Hearing Aids, which both lays out the problem, and more importantly, provides the precise, elegant solution.
Here is Karen’s entire essay in The Limping Chicken, reprinted with permission, with our Editor’s Notes in maroon interspersed:
Every time Andy Palmer (Deputy Editor) asked me to tell the story about my experiences with digital hearing aids I have always turned him down – it was always too difficult to talk about.
About 15 years ago I finally got my letter to start the transition process to move from analogue to digital hearing aids, we were all excited and there had been a lot of positive press. I guess for a lot of people it was a wonderful breakthrough but for me it turned out to be a very long nightmare. [Editor’s Note: If it ain’t broke, keep fixing it `til it is.]
15 years later, I feel like I have been left on a rollercoaster ride that I can’t get off. It hasn’t been a very pleasant experience at all.
I have been left feeling that I haven’t succeeded to adjust because of some unknown psychological reason which has created a barrier in the transition process. [Editor’s Note: As will be explained in a few moments, there is a physiological reason.] That label does not leave you with a nice feeling. I just cannot live with the sound.
I had lived with analogue hearing aids for most of my life, whilst I did have the usual problems that come with being deaf, my hearing aids were just another set of ‘ears.’ I never even thought about them when I wore them; they were just another part of me.
Today, that feeling is but a memory. I am faced with a very uncertain future and so far there is no answer in sight – all is not lost though.
Being of a woman of faith, I see digital hearing aids as my Goliath; another giant in life to face and overcome with God’s help. So I will plod on in the hope that one day I will somehow get there.
So, if you were to ask me ‘are you wearing a pair of digitals now?’ the answer is a big yes.
A wonderful lady at my local hospital, who persevered and gave a lot of time up for me, finally found ones that worked for me. They aren’t perfect, I did have to spend time adjusting and they didn’t give me what I was used to with analogues but the important thing was that I walked out of that room and didn’t even have to come back for any tweaking.
I managed with them, knowing that they were, for me, the best of a bad bunch – as the saying goes!
I was given Phonak Areo 211, apparently, a very simple and basic digital hearing aid. This was some years ago, and sadly, they are not made now and they cannot be repaired.
One has already broken down and thankfully I managed to get hold of a couple of spares to keep me going. Currently, one is beige and the other is blue but hey, who cares as long as I can hear with them? That was all that mattered.
Still, I knew I was on borrowed time with these aids so back I went to try again, but this time, I discovered that the digital hearing aid technology had moved at such a pace that the new ones are all very different, and I was back to square one.
In all the years I have been trying different hearing aids, there has been one thing that has stood out amongst all the problems I had and it was this:
I have been told that it takes a good while for the brain to get used to the digital sounds, and it requires perseverance. I understand this. I also understand that many people give up too easily when they first try them but I sometimes feel like I have to shout from the roof tops that I do try. I have persevered but there is a real physical reaction I get when I hear the sounds of a digital hearing aid and I have no control over it.
I have tried wearing one at a time; I have tried the gradual process; I have tried wearing them at low volume but every time the same thing happens. The longer I wear them the more my brain starts to hurt. [Editor’s Note: Karen’s reaction to the compressed sound is common among the severe-profound wearers, as the patient’s cortex has nothing to “grab” due to the poor temporal resolution.]
It feels like all the nerve endings in my head are firing off electrical pulses. My head then feels like a big tight band is around it and I become very lethargic and very tired, like I am on some kind of a sleeping drug, until I get to the point I cannot function. [Editor’s Note: Hearing loss is very tiring, due to cognitive overload.]
The final straw was last year when I did decide to push on further than before and the result was disastrous.
I ended up in the doctor’s consulting room floor, flooding the room with tears and desperately asking for help just to keep those hearing aids in.
I was so determined not to take them out – I wanted to succeed. I was given anxiety tablets and went home after taking my first one. Soon after, I went into a complete meltdown and started suffering terrible paralysing nervous shivers up and down my body.
I didn’t take any more of the tablets but enough was enough! I took the hearing aids out and put my old digitals back on. For several days I couldn’t get out of bed before dinner and wasn’t able to sleep. I have to thank my God that He has brought me through this awful experience and wonderfully I was able to get back to work two weeks later.
How can I wear digital hearing aids if this is what happens? How can I continue going about my normal life dealing with people, talking on the phone and dealing with a teenage daughter.
Maybe this might seem silly but I am now thinking is these are the sort of symptoms people get with noise torture? Or over exposure to sounds? Is it simply over simulating my auditory nerves with noise it has never experienced before which brings on this anxiety? I just don’t know. [Editor’s Note: Apparently, neither do Karen’s audiologists.]
I have been waiting now for more than six-months for my hospital to come back to me with a suggestion of what to do next. I live in hope that a solution can be found before these old hearing aids finally give up and the rollercoaster begins again. [Editor’s Note: Yes, there is a solution, but some NHS audiologists are not aware of it…]
For severe & profound hearing loss where speech envelope preservation is required due to loss of temporal resolution, the ReSound Sparx (and rebadged Danalogic 6090 for Britain’s NHSA) have the ability to re-flash the firmware to disable WDRC processing to make it fully linear so it will properly emulate analog hearing aids… With the benefit of digital feedback reduction and three program slots. Put another way, for the profoundly deaf whose auditory cortex depends on speech presented in an uncompressed manner, the Sparx — when locked into linear mode — allows for as much as 20dB more gain than an analog aid due to its’ digital feedback suppression.B
Other populations that can benefit from truly linear, “analog-like” hearing aids are those who have auditory neuropathy spectrum disorder, poor temporal resolution from a combination of hearing loss and central auditory processing disorder ((C)APD; as can be measured on the audio gap detection test), and also those who have limited working memory capacity, as posited by Northwestern Professor Pamela Souza PhD.2 Another case where speech envelope preservation due to impaired temporal resolution is required is when amplification is attempted with less-severe cases of auditory neuropathy spectrum disorder (ANSD), put forth by Susan Spirakis.3
For much more on this, including how to program for speech envelope preservation, please see the first article in our series, Speech Envelope Detection vs AGC Attack & Release in Hearing Aids (Update 1). In regard to this, our friends at AudiologyOnline.com have a free, brand-neutral webinar related to this topic by the same Pamela Souza PhD on Understanding and Managing Severe Hearing Loss, on Tuesday, August 12, 2014 at 1600 UCT (12:00 pm EDT)C [Link updated for recorded version of this webinar]. We highly recommend you view this webinar, so you can ask questions (free site registration required).D
- Karen Stockton: Not everyone can adjust to digital hearing aids after a lifetime of analogue, The Limping Chicken, February 24th, 2014
- 20Q: Cognition Measures — They Might Change the Way You Fit Hearing Aids Interview of Pamela Souza PhD by Gus Mueller PhD, Audiology Online, August 6th, 2012
- Auditory Neuropathy Spectrum Disorder and Hearing Aids: Rethinking Fitting Strategies, Susan E Spirakis AuD, Hearing Review, October 2011
A) Tip of the hat goes to Gemma Leadbetter, Senior Audiologist at the Dumfries and Galloway Royal Hospital clinic who alerted us that the Danalogic 6090 hearing aid supplied to their NHS is a rebadged GN ReSound Sparx. She writes on the first article in our series, “What an interesting article: It explains perfectly why my prelingually deafened patients can’t get enough of these aids… Linear all the way!”
B) Oftentimes when describing hearing aids the terms “analog” and “linear” are confused: Although almost all digital hearing aids are non-linear (i.e. have WDRC), in fact some analog hearing aids also have input compression (AGCi) (and the K-AMP from Etymotic Research is a true analog WDRC circuit); and as we pointed out above, the Sparx/6090 digital hearing aids can be configured to operate in a true linear fashion. This is why both users and hearing aid professionals must be careful when using these terms;
C) AudiologyOnline Course #23839 (live) and #24805 (recorded) Abstract:
Among all individuals with hearing loss, patients with severe hearing loss are the most significantly impaired, and the least successful with hearing aids. And there is no “typical” patient – communication ability varies widely, as does hearing-aid success. In this presentation we explore the abilities, challenges and possible solutions for adults with pure-tone thresholds between 60 and 90 dB HL. We will discuss common etiologies, pure-tone sensitivity, dynamic range, assessment of dead regions, and objective and subjective speech-recognition abilities. We will also consider fitting options, including a (sometimes surprising) sample of the technology use by patients in this group;
D) AudiologyOnline.com is perhaps the very best resource for audiologists, hearing aid professionals, and the hearing impaired community in general. Their articles and webinars are all free (free site registration required); and if you need professional CEU’s their $99 annual “all you can eat” price is the best bargain in hearing healthcare. If you haven’t registered with them yet, here’s the link to do it now.