- In this video, I'm talking about how your hearing aids
reduce 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
on how to make you a better informed consumer.
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make sure you hit that subscribe button.
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By far the biggest concern of individuals with hearing loss,
is being able to hear and understand speech again,
in a background noise situation.
And because this concern is so large,
hearing aid manufacturers spend considerable
time and money developing hearing aid technologies
to reduce background noise as much as possible.
But before I get into how hearing aids
actually reduce background noise,
it's very important that you understand
signal-to-noise ratio loss, otherwise known as SNR Loss.
SNR Loss is calculated by performing a speech and noise test
like the QuickSIN.
This is when you're presented with a list of sentences
and you have to repeat those sentences back
as accurately as possible.
But with each sentence, increases the background noise.
So you're really trying to filter that speech
from all the noise,
simulating like a noisy restaurant.
The scoring of SNR Loss is in decibels.
It goes from zero decibels, up to 26 decibels.
The lower the number, the better you hear
in a background noise situation.
The higher the number, the worse you hear
in a background noise situation.
Now let me give you some context
by giving you a real world example.
Let's say that you go into a restaurant,
and that restaurant has a background noise of 80 decibels.
And let's say that you score
on the QuickSIN test a 10 dB SNR Loss.
What that basically means is that
when you have an 80 decibel background noise,
you need speech to be 10 decibels louder,
than that 80 decibel.
So 90 decibels, in order for you to be able
to understand speech as well as a normal hearing individual.
So it stands to reason that
if you can reduce your SNR Loss score
from a 10 down to something lower than a 10,
that you should be able to understand speech better
in a background noise situation.
And there are several ways to accomplish this.
You could simply just reduce the distance
between you and the person that you're talking to,
in that background noise environment.
This way, the amplitude of their voice increases for you,
which can help you do a better job of separating out
their voice from the background noise.
You could have your hearing aids program
using Real Ear Measurement to verify
that your hearing aids have been programmed appropriately
to your hearing loss prescription.
There have been studies that have been published
that show that when you have real ear measurement
performed on your hearing aids,
that it significantly reduces your SNR Loss score.
You should always be making sure
that you can see the mouth of the person
that you're talking to,
because you obtain visual cues of speech information
that can help you fill in the gaps
of what you're not hearing.
And you could wear hearing aids
that use digital features to help reduce
the negative impact of background noise.
Hearing aids manage background noise in two different ways.
The first way is to use directional microphones.
Directional microphones allow a hearing aid
to pick up sound, an amplified sound,
from a very specific direction.
So imagine that you're in a noisy restaurant,
and you're sitting across the table
from a person that you wanna hear.
Well you have a bunch of noise in there,
so you don't wanna amplify everything.
You only want to try to amplify
the person that you're talking to,
so those directional microphones
focus on that person's voice,
amplify their voice,
without trying to amplify those other sounds
that are around you.
Since directional microphones were developed,
this technology has significantly improved,
to the point now where you don't really have to switch
into a very specific program to utilize them.
Usually, the acoustics environments will tell a hearing aid
to switch over into this directional microphone program,
in order to give you hands-free better hearing
in these noisy environments.
These directional microphones typically improve
your signal-to-noise ratio loss,
by about three to six decibels.
Which might not seem like a lot,
but that is actually a really big deal
when you're in a noisy environment,
and every little bit helps.
So let's imagine again that you have a 10 dB SNR Loss.
Imagine if you could reduce that by six decibels
to get you down to a four.
Now just for some context here,
the range between zero and three is technically normal.
So if you get yourself all the way from a 10 to a four,
that is a significant improvement in your ability
to understand speech in a noisy environment.
Now the second hearing aid feature
is digital noise reduction.
This is when a hearing aid identifies
that you're in a noisy environment,
and tries to allocate less amplification
to that background noise,
whilst trying to preserve speech information
in that same environment.
To understand this, we need to discuss
the frequency response of noise,
versus the frequency response of speech.
Noise tends to be steady state.
Think of when you turn on a fan.
That fan stays at the same steady level of intensity,
the entire time that it's on.
If you were to measure the frequency response
of this fan noise,
you would see a relatively flat response,
like you see in this image
on the left hand side of the screen.
However, the frequency response of human speech,
is much more variable,
and has many more pauses and fluctuations and inflections,
like you see illustrated here,
on the right hand side of your screen.
This is how a hearing aid can determine
which channels it wants to reduce
because they have background noise in them,
and which channels it wants to preserve
because they contain speech information.
Now I know that I just introduced
a new term here called channel.
So let me see if I can simply explain what a channel is.
Anytime that a sound comes into a hearing aid,
that sound needs to be processed.
And that sound would be broken up into little chunks,
across the frequency spectrum of that sound.
So think of like a piano keyboard,
and every key being one of those channels.
So when those sounds come in,
let's just say that you have a hearing aid with 20 channels,
you would have 20 little buckets
that that sound would be categorized into,
when it comes into the hearing aid.
Now let's say that that signal that came in,
has noise in a few of those channels,
and it has speech in a few of those channels.
So what the hearing aid would want to do with that,
with digital noise reduction,
is to remove or reduce the amount of amplification,
given to those little buckets or channels,
that has only noise in it.
This way, you can effectively reduce the noise,
and still leave the speech information available
for the hearing aid wearer to hear and understand.
Now we have the ability to measure
how much digital noise reduction
a hearing aid can actually accomplish.
And we can do this in one of two ways.
We can either use Probe microphone measurement equipment,
the same equipment that we would use
to perform real ear measurement,
or we can use a hearing instrument test box,
to have a little control environment
to run a few experiments on,
to see how much reduction of background noise
that hearing aid is capable of.
When we use a test box to measure noise reduction,
we play a steady state noise like speech babble,
or speech-weighted pink noise.
And we see how much reduction that the device provides.
As you can see, it takes a few seconds
for a noise reduction to activate.
And when it does, you can see the reduction
in the amplification given to that particular noise.
And it gives you a measure of how much
noise reduction occurred in decibels.
The amount of noise reduction
can be manipulated in almost every name brand hearing aid.
Now it's important to understand that
just because you're getting noise reduction here,
it does not mean that you're improving
signal-to-noise ratio loss.
And it also does not mean that
more noise reduction is always better.
You can get into situations
where you can have too much background noise reduction,
or digital noise reduction,
and you can get into situations
where you can have too little.
In fact, most research studies suggests
that digital noise reduction algorithms,
simply improve listening comfort
and perceived sound quality,
they do not necessarily improve speech intelligibility,
or signal-to-noise ratio loss.
So you might be asking yourself,
if you're not going to achieve
better speech intelligibility,
or reduce your signal-to-noise-ratio loss score,
then does digital noise reduction
even make any sense to use?
And the answer to that is, maybe.
Because it depends on how much auditory comfort
you're looking for in that particular situation.
This is why it's so important to have important dialogue
with your hearing care professional,
so they can identify how much noise reduction
makes sense for you.
Now after you've maximized
your performance in background noise
with whatever hearing aids that you have,
if you're still not performing at the level that
you want to perform in in a noisy environment,
then you are left with no other option
than to use an assistive listening device
like a remote microphone.
A remote microphone will significantly improve
your ability to hear and understand speech,
in a background noise environment,
and you will get more signal-to-noise ratio loss improvement
from a remote microphone,
than you will with even the best
hearing aid in the world programmed perfectly.
All right, at this point, hopefully
you have a better understanding
of how hearing aids are actually trying
to remove background noise for you,
so you can ultimately hear better.
All I can say is that I highly recommend
that you consult with your hearing care professional,
to ensure that all of the settings inside
of the programming software for your hearing aids,
have been optimized so you can hear your 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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