The Impact of Cochlear Implants on Voice and Speech Production – Interview with Simin Soleimanifar

cochlear implants voice speech quality
June 13, 2023

This week, Andrew Bellavia is joined by Simin Soleimanifar, a research scientist and product specialist at the University of Illinois Urbana-Champaign. They explore Simin’s research on voice perception and speech production in cochlear implant (CI) users.

The study involved recording the voices of 13 individuals with bilateral CI devices and analyzing their ability to control volume variations during sustained vowel vocalizations. The findings revealed that CI users experienced higher voice variation compared to normal hearing individuals, indicating a disrupted vocalization auditory feedback loop. The interview highlights the implications of these findings for CI users’ communication and vocal health, emphasizing the importance of audiologists, speech language pathologists (SLPs), and interdisciplinary collaboration.

Full Episode Transcript

Hello everyone,

and welcome to this episode.

of This Week in Hearing,

I have with me

Simin Soleimanifar

She’s a research scientist and

product specialist at the

University of Illinois at


and she’s going to share her

search that she’s done on

cochlear implants and how it

affects the way people speak.


please introduce yourself and

share more. Hi, Andrew. And hi,


Thank you for having me here

today. My name is Simin.

I’m thrilled to be here as a

guest on this amazing podcast.

A little background about me is

that I got my Bachelor’s and

Master’s degree in audiology and

then I started my PhD program

and speech and hearing

science at U of I.

Now I’m approaching the end of

my program and I’m working

on my dissertation,

which I’m excited to

talk about it today

I’ve dedicated the

research my research area

focused on hearing impaired


specifically those with

cochlear implants.

And today I’m excited to share

insights and conclusions

from my research.

And thank you again for

having me today.

And I’m ready to jump right in

and explore the fascinating world

of hearing care and cochlear

implants. Well,

it’s a pleasure to have you.

It was my good fortune to hear

some of this research at the

Project Voice conference


And so I’m really excited

for listeners,

especially hearing care


to understand more about

what you did.

Let’s start by explaining what

was the problem that you were

looking to investigate when you

embarked on this research.

Sure. So as I said,

my research focuses on

cochlear implants.

So for people who are not

familiar with this technology,

I’m going to just give you

a brief description.

So cochlear implants are like

tiny medical devices that are

implanted into our inner ears to

provide a sense of sound and to

restore the hearing to normal

level for people with severe

to profound hearing loss.

And these devices consist of an

external part, an internal part.

They convert like acoustic

signal to digital version and

they can be implanted

on both ears.

We call it bilateral or just one

ear that we call it unilateral

implantation. Well,

so far the majority of research

has been focused on evaluating

the impact of these devices

on speech perception or on

localization or other perceptual

abilities in cochlear

implant users.

And these studies have

constantly showed a significant

improvement of cochlear implants

on speech perception,

either in quiet or noise or

localization or these

types of areas.

And also they show that the use

of using both devices

cochlear implants


Has greater benefits compared to

just having one ear

and one device.

Because bilateral devices,

they can give you more natural

and enhanced listening


They can resemble binaural

hearing abilities that normal

hearing listener has.

But the question here is that

how about their voice?

Voice in hearing impaired and

specifically those with cochlear

plants is an area that received

less attention.

So that was the first question

that brought me to

this research.

I’m going to go a little

bit into details.

So we know that we perceive,

and then what we perceive that

it can change what we produce.

You could hear yourself and then

monitor yourself and then you

can correct the errors in your

speech production real time

while you are hearing yourself.

So this is called speech

perception and production loop

and it can be activated by

different types of feedbacks.

And the most important one

is auditory feedback.

So we know that CI users have

access to auditory feedback even

to a limited extent

after CI surgery.

So compared to before

getting CI,

they’re going to be better in

monitoring their voice.

But the problem is that they

still show some struggles and

problems with certain type of

vocal task or certain types

of their voice features.

So they could have robotic

or monotonic voice,

making it difficult for others

to understand them.

They may have difficulty

regulating their speech,

their speech level,

their loudness level,

and it leads to further

communication barriers for them.

And these challenges,

they can have impact affecting

their social interactions,

job opportunities and overall

quality of their life.

So if you have worked with them,

you might notice that they may

complain about the level of

their voice and they’re not sure

that how loud or soft they’re

speaking. Right?

So I was wondering that what is

the effect of using these

devices specifically both

together on their voice and on

their ability to control the

volume of their voice?

So that was the big picture of

what I did in my research,

their specific goal.

It’s interesting,

when I first heard you say

that at the conference,

I had to think a little

bit about

internalize what you said.

And I realized a good example of

that for people to consider

is when you wear occluding

earphones or even if you wear

I’ve tried lots and lots of

hearing assistance devices

and what now became.

over the counter hearing aids.

And if they’re occluding


you tend to speak more quietly.

And so I would take these to a

loud restaurant and wear

them and try them out,

and my spouse would be on the

other side of the table,

and she’s like,

you have to talk louder.

You have to talk louder,

because the perception of my

voice was different than

what she was hearing.

And so that makes

a lot of sense.

And I know even hearing aid

people have to work feeding a

natural amount of voice into

people’s ears so that their self

perception is accurate.

But I understand with

cochlear implants,

because you’re not necessarily

100% mitigating really severe

profound hearing loss,

because that’s the state of

cochlear implant technology.

This could become a

real problem. Now,

you had some collaborators when

you did this research too,

who was involved in it?


I’m working in Binaural

hearing lab at U of I,

and my supervisor is Dr.

Justin Aronoff.

We’re together running

this project.

There are some other students

involved in the lab,

and we recently are


We are using Cochlear Americas

brand in our research,

and we’re looking forward to do

the same research with

other brands.

Everything is going

on in our lab.


got it.

And so then how actually did

you conduct the research?

What was the structure

of the research?

And how did you go about

determining people’s self voice

perception and its effects?

Yeah, that’s a great question.

So we recorded the voices of 13

individuals with bilateral

cochlear implants. As I said,

they all had the same brand,

Cochlear Americas,

and they performed a sustained

vowel vocalization test.

So I recorded their voice while

producing twelve American

English vowels

in three different conditions.

And they were randomly chosen.

So the conditions were using

both devices together while

producing the vowel,

and then using each ear

individually and alone,

right ear alone,

and then left ear alone.

And to see how good they are at

controlling the variation

of their voice volume,

we use a metric that is called

variation of peak amplitude

or VAM.

That is a measurement of long

term control of amplitude


And it actually shows the

stability of loudness,

or volume over a waveform.

And having higher value

of this metric,

it means having greater

variations or less ability,

poorer ability to control the

volume of your voice.

So actually,

we were looking for

smaller values.

A smaller values means

better control.

Okay, yeah,

that was the method that we

used for our research.

And so then did you find

that people spoke

with a consistently different

volume or their volume was

actually wavering as they spoke.

Yeah, exactly.

So what we saw was that the

results of this study showed

when CI users,

they use their devices

to vocalize,

they show a high amount of

variation in their voice in

their waveform. So, for example,

like a normal hearing listeners,

they easily can keep their voice

at a fixed level and produce

a long vowel

for like 5 seconds

or maybe longer.

And you can see a smooth and

flat waveform in their voice.

They’re just like, say,

without any going up and back.

But what we saw for CI users,

either bilateral CI users

or unilateral ones,

we saw a lot of variation in

their voices compared to normal

hearing listeners.

They couldn’t fix their voice

at the same level.

They were a lot of


going up and down peaks

and valleys.

But that wasn’t the only fact

or finding of this study.

The most interesting one was

that as soon as bilateral CI

users switched to use

just one device,

they got better at controlling

their voice.

We could see

lower amount of variation,

loudness and volume variation in

their voice as soon as they turn

off one of the devices.

So it’s kind of like,

contrary to popular belief

that we’re saying,

having two devices is kind of

like resembling having two ears.

And you can get better

at speech perception,

but when it comes to

speech production,

it’s kind of like we

can see conflicts.

We can see that


when they use just one device,

they can get better at

controlling their voice.

And this is not just on level.

So we previously did a research

in our lab and we saw kind of

the same effect for the

pitch of their voice,

how they can be accurate

at singing,

how they can keep the pitch of

their voice at a specific level.

And again,

we saw that they’re pretty good

with using just one device

compared to both device

in voice test.

So the general conclusion of

this research was that it seems

that using both devices,

although it has its own benefit

in perceptual tests,

but it seems that it’s

negatively affect their

voice in CI user.

So that seems to imply that the

vocalization auditory feedback

loop is actually broken. Right.

So, like,

I use the example of occluding

earphones – okay,

it caused me to speak

at a lower volume.

It was consistent volume,

just lower,

and with a little

bit of practice,

so I could raise my voice and

speak so other people could hear

me wearing an occluded earphone.

But, you

are implying really that the

whole feedback loop is broken

if both volume and pitch are

wavering all over the place,

would you draw that conclusion?

And if so,

are there actually any remedies

for that? Yeah, absolutely.

The reason is not clear

enough yet,

but what we assume is that there

might be a mismatch in loudness

cues that they can get from each

ear. And as I mentioned before,

what you perceive can reflect

on your production.

So if you get mismatched

cues from each ear,

it makes a confusion when you

want to produce like a vowel or

a word or like long sentence.

It could be because of auditory

mismatch, as you mentioned,

between ears.

It could be even like

neural health.

You might have a better neural

health in one of your ears.

This is not something that

can get easily fixed.

But for remedies,

what we can do firstly is

that CI manufacturer,

they can work on syncing to two

devices at the maximum rate.

So if we can get the same

cues from each year,

I assume that it kind of solves

the problem to a great extent.

But then when it comes to voice

experts or speech language


I kind of have some takeaways

for them that I can mention

later in our discussion. Right,


So the immediate takeaway is

that it’s more about the

mismatch than it is the function

of the CI itself. Right.


are there things that hearing

care professionals can do in the

adjustments in the settings of

the CIs in order to get the

perception of the voice more

matched on one side

versus the other?

Or is that really an issue

for the manufacturers?


it depends on CI manufacturer.

But voice expert and speech

language pathologist,

they can work to train CI users

to constantly monitor their

voice consciously.

So I’m going to briefly first

talk about a little bit about

impact of this issue on their

communication life.

So having problem with

volume control,

it can impact their

communication. For CI users,

for example,

speaking too loudly

or too softly,

it can make it difficult for

others to understand them.

It can also make fatigue or

discomfort for listeners

or speaker.

And I had some CI users that

saying they assume they’re

talking like normally by

reading other people,

like facial expression,

they realize that they’re too

loud and they lost their

interest in conversation.

You know, and also like in,

in consistent like volume,

it can make it harder for

listener to follow the follow

up conversation.

And it becomes very important

when you are in a group setting

or when you are talking

about a complex topic.

But more important thing is that

CI users are at a risk of

developing voice disorders.

So these disorders can happen

because of increased strain

placed on their vocal cord when

they speak with high volume

variation and these strain,

they can lead to hoarseness,

vocal fatigue or other vocal

problems and disorders.

So CI users,

they may experience discomfort

or even pain when they speak.

So that’s why that I wanted to

mention this before talking

about takeaway for hearing care

professionals because it’s

really important to diagnose

their voice disorders from the

earliest stages and avoid

leading to further disorder

and disabilities for them.

Here are a few takeaways

that I have.

Hearing care professionals,

they should evaluate and monitor

their patients voice quality as

part of their regular

and overall care.

And by incorporating voice

evaluation into a routine


they can identify difficulties

in their patient’s voice

quality. Also audiologists,

they can tailor CI reading to

change the settings

to the way that

they can maximize matches

between the cues that

participants get from each year.

So part of it on our

audiologists in the hearing care

team and then education and

counseling also is

very important.

Professionals could educate

their patients about the

potential changes in their voice

quality and the importance

of vocal health.

I had some CI users in the lab

that they had history of

alcoholism or smoking and their

voice got worse than their other

peers in the same group of

hearing impaired community.

So they should care about their

vocal health and also hearing

care professional,

they can provide strategies

and some exercises to help

patients improve their vocal

health and change the overall

of their communication.

And also collaboration and

interdisciplinary approaches

is very important.

Hearing care professional can

work closely with speech

language pathologists,

with vocal therapists and they

can develop some treatment plans

that it can both address the

auditory need and the

vocal aspect of.

Communication for CI users.

So they were some takeaways

from this research. Okay,

that’s really interesting.

And what I asked earlier that if

the feedback loop was broken

isn’t really true.

It’s only that when you

have the mismatch,

you don’t know how to

interpret that.

And so you’re going to waiver

all over the place.

But it sounds like then with

appropriate training,

say from a speech language


you can actually work within

the new feedback signals,

if you will,

and learn how to modulate and

control the pitch of your voice,

even so, is that correct?


So as we talked in Voice AI

Conference, so professionals,

they can explore the integration

of voice AI technology

into their practice.

So voice AI systems can provide

real time feedback on various

aspects of a speech,

like speech loudness intonation.

So by using these tools,

like hearing care professionals,

they can empower their patients

to self monitor and to make

adjustment to their speech.

And it will ultimately improve

their voice quality. So,

for example,

if the voice AI can just monitor

their voice for a long time,

for a long, late period,


the voice expert,

speech language pathologist

and the hearing care team,

they can monitor the changes

in CI users voice,

and they can teach them how they

can make adjustment to make

their voice fixed in

the same level.

So there are some training

methods that they can absolutely

use to improve their voice

quality and communication

skills. Okay,

so in addition to in person

training and rehab from an SLP,

you’re saying there are also

these sort of AI based tools.

Are they already available or is

that something that

would be possible?

I think both. So as I heard,

I’m not very familiar with the

technology, but as I heard,

there are some technologies

that they’re launched,

but they are planning to just

get it better and better,

become better and better.

So I think it’s not ready to

use like in a larger scale,

but I’m hoping that very soon

they can just be very useful.


Which is really interesting

because I know at least one of

the CI manufacturers has an aural

rehab program already that can

be used to complement in person

rehab and training.

And so what you’re saying is if

these sorts of AI based tools

are built into those,

people can do additional kind of

like physical rehab, right?

Do additional rehab at home with

the tools in addition to having

in person rehab with an SLP,

and therefore improve the way

they vocalize. Is that correct?

Yeah, exactly. Because voice AI,

they can provide feedback

and they can be like a kind of

like personal coach for our CI.

users. Many of my subjects,

they have desires to sing

or play in a band.

So just imagine such

a monitor system.

They can help them to sing or

play in tune. So, yeah,

besides having or participating

in rehabilitation programs,

they can have their own personal

coach at their home,

which is really interesting,

because in thinking of the

greater lifestyle and well being

of a person is more than just

listening one on one with a

hearing aid or a cochlear


It’s all the other things they

do in their life, too.


A full life. Yeah.

They really have desires

to sing.

I have a lot of subjects

in the lab that,

before getting CI or before

becoming deaf,

they were playing they were

playing some instruments

or they were singing,

but they couldn’t after that.

So they really would like to

enjoy different aspects

of their lives,

and I think they deserve it.

So I’m very looking forward to

see how technology can be

integrated in their lives and

improve the quality of

their life. Well,

this is a really fascinating

line of research,

and I can really see how

it will, in the end,

help CI users lead a fuller

and more enjoyable life.

And all the different

things that they do,

whether it’s music,

the way they interact


and how important it is to be

able to hear and speak

well professionally,

lots of different parts of a

person’s lifestyle that this

research has the potential to

affect in a positive way.

It’s terrific,

and I look forward to seeing how

this all plays out in terms of

the therapies and the

tools you named.

So I appreciate you coming

on to explain that to us.

Do you have any closing

thoughts for people?

No. Thank you so much, Andrew,

for having me on This Week in

Hearing today.

It’s been a pleasure to share my

research and decide with your

audience and yeah, that’s it.

Thank you.

And if people want to engage

with you after hearing this

podcast, how do they reach you?

They can check my LinkedIn page.

All of my contact information

is on my LinkedIn account.

And yeah,

actually so we’re recruiting

for CI users in the lab.

So if any of these people are

watching this podcast,

I would love to invite them

to come to our lab.

We’re doing a lot of different

experiments and for hearing

care professionals, teams,

they can reach out to me sure,


On my LinkedIn account. Well,

thank you, Simin.

I appreciate you coming on

and everybody watching.

Thanks for tuning in. Thank you.

It’s been a pleasure.

Have a great day, Andrew.

Same to you.


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About the Panel

Andrew Bellavia is the Founder of AuraFuturity. He has experience in international sales, marketing, product management, and general management. Audio has been both of abiding interest and a market he served professionally in these roles. Andrew has been deeply embedded in the hearables space since the beginning and is recognized as a thought leader in the convergence of hearables and hearing health. He has been a strong advocate for hearing care innovation and accessibility, work made more personal when he faced his own hearing loss and sought treatment All these skills and experiences are brought to bear at AuraFuturity, providing go-to-market, branding, and content services to the dynamic and growing hearables and hearing health spaces.

Simin Soleimanifar is a researcher in Speech and Hearing Science, specializing in research and development of hearing medical devices. Her work ranges from conducting feasibility studies to integrity testing and human studies. She also focuses on high-quality audio systems and voice-assistant technologies, with the goal of connecting people to the beautiful world of sound.




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