- In this video,
I'm talking about how speech and noise hearing aid programs
help you hear your best in background noise.
Coming up.
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Hi, guys.
Cliff Olson, doctor of audiology,
and founder of Applied Hearing Solutions
in Phoenix, Arizona, and on this channel,
I cover a bunch of hearing-related information
to help make you a better informed consumer.
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make sure you hit that subscribe button.
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It should come as no surprise that the hearing aid programs
that are designed to help you hear better
in a quiet situation are not the best programs
that help you hear your best
in a background noise situation.
It is for this reason
that all major hearing aid manufacturers
have speech in noise programs
that you can manually switch into with your hearing aids,
or they can be switched into automatically
by your hearing aids.
But what do these speech and noise programs actually do
to help you hear your best in background noise?
Well, I'm gonna get into that, but before I do,
there are a few key concepts that you need to understand,
and the first one that we're gonna talk about
is signal-to-noise ratio.
Signal-to-noise ratio, which is abbreviated SNR,
is the ratio of the signal or speech that you want to hear,
versus the noise that you don't want to hear,
and this ratio is often expressed in decibels.
For instance, if you have a signal-to-noise ratio of 1:1,
it means that the signal that you want to hear
is at the exact same level
as the noise that you do not want to hear.
You can also express this in a single digit,
and in this case of a 1:1 ratio, that digit would be zero,
meaning that there is no difference between
the signal and the noise.
If you use the single number SNR value
like you typically see in research studies,
then if you have a signal
that is five decibels louder than the noise,
you have a +5 SNR.
On the other hand, if you have noise
that is five decibels louder than the signal,
then you have a -5 SNR value.
All that being said,
you basically want the highest positive SNR value,
which means that you have significantly more signal
than you do noise.
And for every single decibel of increase of the signal,
it roughly translates into
about 10% improvement in word recognition.
Another concept that you need to understand
is the upward spread of masking.
Upward spread of masking is a phenomenon that occurs
when low frequency sounds drown out
or mask over high frequency sounds.
Since basically all sounds
need to enter the cochlea at the oval window,
low frequency sounds have to pass through
the high frequency ranges of the basilar membrane.
This means that really intense low frequency sounds
can inadvertently mask over high frequency sounds,
preventing you from hearing them optimally.
Since high-frequency speech information
is critical for understanding speech
in a background noise situation,
upward spread of masking can be detrimental
to performance in background noise.
Okay, now that you have a very basic understanding
of these two different concepts,
I'm gonna go ahead and get into
what hearing aid manufacturers do
in these speech and noise programs
to help you hear your best in background noise.
The first thing that speech and noise programs do
to help you hear better in background noise
is something called directionality
to improve your signal-to-noise ratio.
With two microphones on a hearing aid,
one in the front and one on the back,
it helps that hearing aid identify
which direction that sound is originating from.
So if sound is coming from the front,
it will strike the front microphone,
then the rear microphone, and it will tell that hearing aid
that that sound originated from in front of it.
However, if you have sound that comes from the rear,
it strikes the rear microphone
milliseconds before it strikes the front microphone,
telling the hearing aid
that that sound came from behind you.
To take this a step further,
if you have a hearing aid on your other ear as well,
you technically have four microphones,
so now no matter which direction sound is coming from,
the timing difference between
any one of those four microphones
helps those hearing aids determine
which direction sound is coming from.
Why is directionality so important
inside of a speech and noise program?
Well, it allows you to actually face the person
that you want to hear, and amplify their voice,
versus amplifying all of these other sounds around you.
The degree or width of this pickup range
can be specifically programmed
in this speech and noise program
by your hearing care professional
to make sure that they have it dialed in
exactly to your needs.
Directionality could improve your signal-to-noise ratio
typically anywhere between one and four decibels,
which is between a 10 and 40% improvement
in a background noise situation.
And of course, this does depend
on the type of dome that you use on your hearing aid,
or the size of vent that you have
on your custom ear mold on your hearing aid.
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And now, back to the video.
The second thing that speech and noise programs
do to help you hear your best in background noise
is employ noise reduction algorithms.
Noise reduction is simply reducing the amount
of amplification to background noise
by using digital signal processing.
A speech and noise program can typically
identify background noise by its steady state nature.
When you think about it, a lot of noise sources
do not have a lot of peaks and valleys in them.
So when you think about a vehicle running, or a fan running,
or an air conditioner running, or even a noisy restaurant,
there's not a whole lot of fluctuations in that noise.
In contrast to that, you have human speech
that has a lot of different peaks and valleys
when someone's talking to you.
It is this difference between
the peaks and valleys of human speech
versus the steady state nature of noise
that allows noise reduction to work.
Hearing aids will pick up all of these different sounds,
and it has to basically categorize
all of those sounds in channels or buckets.
All of the buckets that have just noise
get reduced in the amount of amplification
that's given to them.
All of these buckets that has speech
or speech and noise are kept elevated.
So what happens here is that you get accentuated speech,
but reduced background noise.
Now, this often makes noisy situations more tolerable.
It does not necessarily improve your ability
to understand speech in those environments.
The level or amount of noise reduction
that is utilized inside of a speech and noise program
can be adjusted by your hearing care professional.
If you do not tolerate noise well,
then you will typically want
a very high amount of noise reduction.
If you do tolerate noise well,
then you typically want to keep this noise reduction low,
as to not interfere with audibility for certain sounds.
The third thing that can be done
in a speech and noise program
to help you hear your best in background noise
is to reduce the amount of low frequency amplification
that you get to prevent the upward spread of masking.
If we were to go into a noisy restaurant
and measure the amount of noise in that restaurant,
we would typically identify that that noise
isolates more in the low frequency ranges.
So if we end up amplifying low frequencies too much,
you guessed it, we can over amplify them,
and actually drown out these high frequency sounds
that your brain uses
to separate speech from background noise.
However, you do not always want to limit
the amount of low frequency amplification
if you have a hearing loss in the low frequencies,
because you may need that low frequency speech information
when you're in more calm, quiet environments.
And this is exactly why we have
these different speech and noise programs
so you can use these features when you need them.
And the fourth thing that can be done
inside of a speech and noise program
to improve how well you hear in background noise
is to make sure that you have
a higher maximum power output setting.
Maximum power output, otherwise known as MPO,
is basically the ceiling of amplification
that you can get from a hearing aid.
And you might think that you want to lower down the MPO
in a noisy environment,
'cause you don't want to subject yourself
to all of that noise, but if you have the MPO set too low,
it can actually restrict
the peaks of amplification for human speech,
which can prevent you from actually understanding
the person you're talking to in a noisy environment.
Sometimes the default MPO settings,
or even lower than the default MPO settings,
are sufficient enough
when you're in a calm, quiet environment.
But when you go into a background noise situation
and you start using a speech and noise program,
if you have MPO settings that are set too low,
it can actually restrict speech information
that prevents you from hearing your best
in those environments.
At the same time,
you do not want your hearing care professional
just to crank up all of the MPO settings
on your hearing aids.
They need to be methodical about this
to make sure that they're not
just completely over amplifying all sounds.
Different hearing aid manufacturers
will utilize these different features in different ways
inside of their speech and noise programs
to make sure that you get
the best speech understanding possible,
and the most auditory comfort possible.
All this being said, something else that should be done
by your hearing care professional
for them to optimize your speech and noise program
for a background noise situation is real ear measurement.
Real ear measurement simply a way to verify
that you're getting the proper amount of amplification
for your hearing loss prescription
during hearing aid programming.
In a 2012 study, it was identified that hearing aids
that were programmed using real ear measurement
resulted in a significant improvement
in the ability to understand speech and noise.
You can also see here
that when real ear measurement is not performed,
even an old analog hearing aid can outperform
even the best digital hearing aids on the market.
So no matter how you set up your speech and noise programs,
with directionality noise reduction,
low-frequency reduction and amplification,
or optimizing your MPO settings,
none of this matters unless real ear measurement
has been performed on your devices.
Now, if you want to learn more about real ear measurement,
then I highly recommend that you check out my video
that I will have linked in the description.
At the end of the day, there is no single setting
that is perfect for any speech and noise program.
You need to make sure that your hearing care professional
is following a person-centered care approach
when setting up your hearing aids
to your specific wants, needs, and preferences.
And if they do,
you'll hear your absolute best in background noise.
That's it for this video.
If you have any questions,
leave them in the comment section below.
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Also feel free to check out my website, drcliffaud.com.
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