Today's hearing aids have the capability of being Auto-Programmed otherwise known as the Manufacturers First-Fit settings. The problem is, these settings are not verifiable because you can only verify a validated hearing aid prescription like NAL or DSL. What is a prescription? Different hearing losses require different levels of amplification at different frequency ranges.
There are a variety of factors that impact this, including severity of hearing loss, age, gender, experience with amplification. Based on years of research, we know that using Real Ear Measurement provides a superior fitting than the settings provided by the Auto-Program button. This was once again confirmed by a study at Washington University: ii. http://www.hearingreview.com/2018/09/...
There are several types of validated prescriptive methods.
1. NAL-R - Used for Linear Hearing Aid Programming
2. NAL-NL1 - Used for Non-Linear Hearing Aid Programming for Adults
3. Nal-NL2 - Updated version for Non-Linear Hearing Aid Programming for Adults
4. DSL - Prescriptive method for children which is now on its 5th version
Ensuring that one of these prescriptions are used and verified inside of hearing aids is critical for performance. These are verified by using a microphone probe tube inserted into the ear canal along with hearing aids to check the amount of amplification coming out of the hearing aid. The problem is, most hearing care professionals do not verify that the prescriptive targets are being met.Hearing Aid Manufacturers aren't stupid. They know providers don't verify fittings. This is why they under-prescribe amplification, particularly in the high frequencies. This creates a situation where patients have improved perceived sound quality but sacrificing speech clarity.
Every time I check to see how close the manufacturer's First-Fit Auto-Settings come to the prescription, they are never close. Example after example in this video clearly indicate poor prescriptive estimates. Even though many people feel that hearing aids can auto-calibrate to a hearing loss, this theory is constantly disproven by verification. Hopefully you now understand why verifying hearing aid programming using Real Ear Measurement is so critical to success with hearing aids. Do not settle for hearing aid fittings that rely on the Auto-Program settings using Manufacturer's First-Fit. This is ultimately setting you up for a sub-par fitting.
This article will look at the difference between hearing aids that are programmed using Real Ear Measurement vs. hearing aids that are programmed using the auto-program button.
This topic might be a little complex for some readers, so if you don’t know what Real Ear Measurement is yet then I highly recommend you check out my primer on the topic before reading this one. https://appliedhearingaz.com/real-ear-measurement/
All hearing aids sold today have the capability to be auto programmed, otherwise known as First Fit. First Fit is when you take the hearing loss of an individual you enter it into the manufacture software and it provides an estimate for how much amplification that individual should receive.
All hearing aid manufacturers have their own proprietary First Fit algorithms to provide a certain amount of amplification that they believe is best from their devices. The problem with this is that you cannot verify a prescription that is proprietary to these manufacturers because third-party verification equipment can only verify certain validated prescriptive methods.
You see, even individuals with identical hearing losses will require different amounts of amplification at different frequency ranges, based on different ear canal size and shapes of those individuals, because no two ears are alike.
To understand why hearing aid verification is so critical, you have to understand what a prescription is. A prescription is basically the amount of amplification that an individual with the hearing loss would require at each individual frequency to ensure that sounds are comfortable and audible for them. Prescriptions take into account a variety of factors from individuals including their age, their gender and how long they’ve been wearing hearing aids.
Based on years of research, we know that verifying hearing aid prescriptions using Real Ear Measurement will improve the way that someone can hear in nearly all situations, including background noise which results in a better overall listening experience for a user. In fact, this research continues to happen, we just had a research study come out not too long ago by Washington University where they did a double-blind study that indicates that users prefer hearing devices that have been fit using Real Ear Verification versus hearing devices that haven’t. If you want to see that research, you can find it here.
The two most common validated hearing aid prescriptive methods are NAL and DSL. NAL is derived from the National Acoustics Laboratory in Australia, and there are three types within this method:
The DSL prescriptive method stands for Desired Sensation Level, this one was derived out of the necessity to have a verifiable prescription for children. Adults and children both require different levels of amplification, and they are now on the fifth generation of the DSL.
Verifying hearing aid programming using one of these validated prescriptive methods will ensure that you’re receiving the proper amount of amplification, for your hearing loss and your individual characteristics like your ear canal size and shape.
Of course, Real Ear Measurement is the gold standard method of verifying these hearing aid prescriptions. With this process, your hearing care provider will place probe microphone tubes inside of your ear canals along with the hearing aids that they are programming. These microphone tubes will record the level of amplification coming out of the hearing aids. By playing a known calibrated signal from a loud speaker in front of you, we can measure to see if the amplification coming out of the hearing aids is meeting your prescriptive targets.
When we look at these measurements in a graph, the prescriptive targets for sound are indicated by a purple hash mark line. Additionally, a solid purple line indicates the sound coming out of the hearing aid after it has been amplified. The goal is to have these two lines overlap as closely as possible.
To compare the accuracy of Real Ear Measurement vs. First Fit, I analyzed at two graphs side by side. One graph showed the two purple lines of a hearing aid that has been fit using manufacturer First Fit settings, and other showed the lines of the same hearing aid after it had been programmed to the prescriptive target using Real Ear Measurement.
When your hearing aid is calibrated to prescriptive targets, that is where you will hear your best. The problem is, the majority of hearing care professionals use manufacturer First Fit method instead of using Real Ear Measurement.
Hearing aid manufacturers are not stupid. They know that two out of every three hearing care providers are not going to use Real Ear Measurement to verify that a hearing aid is fit appropriately to a patient’s hearing loss prescription. So, what do they do? They reduce the amount of amplification particularly in the high frequencies to make that amplification more comfortable for a patient, thereby reducing the likelihood that that patient will return those hearing aids because they don’t like the way that they sound.
I recently did some analysis based on my own work that illustrates what I’m talking about. I produced a graph of the First Fit measures done on hearing aids that were programmed by the manufacturer of software, then I compared this to a graph of how I actually adjusted the hearing aids to, to make sure that they’re meeting a prescription.
The graphs showed that the patient I was working with would have been significantly under amplified in the high frequencies had they stayed with the manufacturer’s recommended settings. Now, there is a chance that this patient would have been somewhat satisfied with this hearing ability, but he wouldn’t perform at his best based on research and he likely wouldn’t perform as well in a background noise situation.
If you don’t have your hearing loss prescription verified using Real Ear Measurement, you really have no idea whether or not you’re meeting your prescription or not. Actually, it’s clear you’re not meeting your prescription. In my experience, I’ve never seen a First Fit estimate even come close to matching a prescriptive target. And this is from some of the most high-tech hearing aids that exist on the market today.
I am not making this stuff up. There are tens of thousands of individuals walking around out there with hearing aids that are not programmed correctly to their hearing loss prescription, because they’ve never had Real Ear Measurement performed on them.
Now, I know that there’s some of you out there that are getting sick of me talking about Real Ear Measurement and how important it is, but the simple fact of the matter is that I’m not going to stop talking about it until 100% of hearing care providers do it on a regular basis.
Hopefully, this article has opened your eyes to the importance of hearing aid verification. Even if it costs you significantly more money, you should demand that Real Ear Measurement be performed at your fitting appointment. If you don’t have Real Ear Measurement performed and you rely on manufacturer First Fit settings, then you are setting yourself up for a poor fit of your hearing devices which will ultimately result in poor performance.