- In this video, I'm talking about how speech
and noise hearing aid programs help you hear your best
in background noise. Coming up. (upbeat music) 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. So if you're into that, make sure you hit that subscribe button. And don't forget to click the
bell to receive a notification every time I post a new video. 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. Hey, guys, sorry to interrupt the video, but I have a huge favor to ask. If you could click the
like button on this video, it really helps the YouTube algorithm recommend this video to more individuals. All that being said, I
really appreciate it. 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. If you liked the video, please share it. And if you want to see other
videos just like this one, go ahead and hit that subscribe button. Also feel free to check out
my website, drcliffaud.com. (upbeat music)
