Technology, Clinical Practice

Unravelling the custom process

In this interview, Stefan Launer speaks to all things custom – past, present and future. We discuss challenges that have been overcome to create smaller products with greater functionality and we look towards challenges and future potential in this realm.

Interview series

Theory to Practice

Interviewee
Stefan Launer
Senior VP of Science and Technology at Sonova AG

Stefan studied Physics at the University of Würzburg in Germany and conducted a PhD thesis in Hearing Science and Psychoacoustics at the Universities of Göttingen and Oldenburg. During his career at Phonak, now Sonova, Stefan managed various teams including Audiological Engineering, Digital Signal Processing & Microelectronics and Acoustic Design. In his current role, he leads the Audiology and Health Innovation program within the Sonova organization. Stefan Launer also holds an Adjunct Professorship in Audiology & Hearing Instrument technology at the University of Queensland in Brisbane.

Stefan Launer, Senior VP of Science and Technology at Sonova AG, has worked in the hearing aid industry for over 20 years. Hear about his views on custom products in the hearing industry in the past, present and future.

 

Hearing aids come in many shapes and sizes, and some include a custom ear piece to deliver sound into the ear. What are the advantages of a custom ear piece over the more standardized domes?

Most of the time custom ear pieces provide much more comfort while wearing them as it’s customized to the individual ear shape. This means they are more comfortable to wear during the day, sits better in the ear canal and provide a better seal in the ear.

By having a better fit to the ear canal you typically also get a better acoustic and more stable acoustic performance. Acoustic and acoustic coupling is an often forgot but important aspect of sound delivery. By providing individually fit shell, you can improve the performance of the devices quite a bit.

 

How can custom hearing aids prevent wind noise? How do you test for wind noise?

The ear has a natural beautiful design to prevent problems with wind noise and that’s why we hardly ever hear it. If you have devices, like hearing instruments, you pick up turbulence like wind noise. This is more of a problem with behind-the-ear (BTEs) and full shell in-the-ear (ITE). The more you get into the ear canal, typically, the better it [the wind noise] gets. It can be a bit tricky as it depends on the precise location of the microphones within the canal; the tragus can cause eddies and if the microphone sits right behind this point this can create a problem. These points are always a consideration when we are modelling custom hearing aids.

We test for wind noise in various conditions, we actually built a wind tunnel within the organization. We had a full team optimizing wind tunnels and ear canals. On this point, it is interesting to note, we often put a lot of emphasis on our more complex features. However, it is important to mention the amount of work that goes into basic product architecture e.g. the material and designs, to optimize for reliability and acoustic coupling, which is something we don’t often don’t focus on. For example, we had a team of people working for 2-3 years to optimize the domes…we had a team working on developing titanium shells…we had a team developing wind canal and acoustic models.

 

Phonak NZ recently did a survey of around 40 clinicians asking them why they selected domes versus custom shells in the first instance for some clients where shells will probably deliver a more optimal result. About 1/3 of them said that they selected domes in the first instance due to concerns about occlusion. What tools do Phonak offer to prevent occlusion in custom products and how does it work?

In custom products we put in a lot of effort to optimize and reduce the occlusion effect. We started with developing models that helped us explain and model this effect. We use these models to predict and optimize shell form of a custom shell to reduce occlusion effect. Occlusion is an acoustic property that can be reduced by opening up the vent, the vent can be opened in various difference forms and shapes, depending on length, size and placement. We developed these models and built this into our RSM shell prediction or shell modelling software. For example, the AOV prescription is an inbuilt algorithm, that, when supplied with the patients audiogram, the RSM can create a ‘target acoustic mass’ to ensure the vent diameter and length (components of acoustic mass) to minimize risk of occlusion and feedback and improve maximal stable gain. Further, in the fitting software, we developed a structured process on how to reduce occlusion. This can be accessed through the ‘occlusion manager’ as well as the ‘automatic fine tuning’ tab.

Typically what we see now is that we have a significantly reduced return rate…people are accepting the devices much better.”

What is the return on AOV vent selection relative to user ‘user selected vent’?

Typically what we see now is that we have a significantly reduced return rate – both ‘return for credit’ and remake rates are significantly lower when AOV vent selection is chosen. This means people are accepting the devices much better.

 

Hearing in noise is one of the most challenging listening situations for people with hearing loss. Directional microphones are a key technology used to improve SNR to support better speech understanding in noise. Phonak recently released Bio-Metric Calibration in the custom Virto range to further improve the performance of these directional microphones. How does Biometric calibration work and what benefits does it provide?

One of the problems in the design of ITEs is that every individual pinna is acoustically very different and has different characteristics and properties. In order to optimize the performance of directional microphones, it is important to take all these micro-acoustic properties into consideration. In biometric calibration, we take the images we get from an ear canal and pinna, to derive a model of the individual acoustics, compare this to a reference model and calculate how to best position the directional microphones. This provides a significant benefit in SNR. More on this found here.

 …every individual pinna is acoustically very different…it is important to take all these micro-acoustic properties into consideration.”

Real-ear-sound, our omnidirectional microphone mode, in BTE instruments is meant to account for the pinna effect that is lost with having directional microphones behind the ear. Do you think the person’s individual pinna information will eventually be incorporated into this algorithm?

That would be an interesting idea to have, this would probably provide some benefit. One of the big problems with real ear sound (RES) and BTEs is the placement of the BTEs behind the ear and what the angle is. A custom mold on a BTE or RIC instrument can ensure that the hearing aid is sitting optimally on the ear each time. Read more about microphone placement here

 

Custom shells are generally made from either silicon and hard acrylic. Phonak recently introduced a revolutionary new material for custom shells – Titanium. What was the driving reasons for this, some of the challenges that needed to be overcome, and the benefits to end-users?

Robustness, reliability and size. Titanium is a much more stable material with much thinner walls. This enables smaller volumes of the devices and get further into the ear canal. This also enables more real estate in terms of fitting larger components

Further, comfort is a big factor. Subjective reports are that titanium is more comfortable to wear, it feels better and nicer on the skin.

 

Were there any challenges in the development of titanium?

There were huge challenges around 3D printing. We had to optimize metal printing significantly for our requirements. When we started with 3D printing using titanium it was nowhere near mass production application due to the technology being new.

Also, in addition to 3D titanium printing, there was a big amount of post-printing processes that needed to be developed. None of it could be purchased – it was all developed in our digital manufacturing department in close collaboration with the product development team. All of this needed to go hand-in-hand.

 

What do you see as potential next big thing(s) for custom products?

There are a few ‘big things’ for custom products.

  • Integrating sensors into hearing instruments is a big topic. This is a huge interest for custom shells, custom designs, custom products. It would be much more of a challenge to integrate sensors into the custom products compared to BTEs due to their small size.
  • Other big thing for custom will be to do with rechargeability and further expanding on the wireless offering.
  • Another interesting topic is certainly the 3D scanning of the ear canal. We have to see what the benefits are and ensure there is a high level of precision. This will be a new learning for everyone involved and we need to ensure it is precise and reliable.
  • And finally, there is potential for more comfortable shell materials (also multi-material) for even more wearing comfort, since we recognize people wear these devices (custom ITEs and custom earpieces) for up to 16 hours per day.

 

Will there be active occlusion compensation in hearing aids?

It’s coming into reach. An active vent requires some space – you need a motor or mechanism to open and close the vent. The challenges around this are not technical feasibility in the lab, but feasibility in real life where you have a lot of moisture and humidity. To get an active vent working in a sustainable and reliable way, is the challenge. Volume is also a limiting factor.

 

Thank you for a truly insightful interview, Stef. We certainly look forward to see what the future holds for custom products  watch this space.

 


Key takeaways from Stefan Launer on the benefits of custom products:

  1. Despite having very good standard domes, custom ear pieces “still rock” 😉
  2. We can significantly improve wearing comfort and retention.
  3. We can improve the acoustic performance by modeling and designing the acoustic properties of the custom ear pieces.

 

Learn about Phonak Virto Black, the first custom-made hearing aid that looks like an earbud, here.

About

Theory to Practice is a series of interviews with experts in the field of audiology and beyond. Interviewees share their knowledge and insights on relevant topics. The special focus of each interview is to translate theory into key take-aways which can be implemented into daily practice.

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Previous comments
  1. Great article, thank you for exposing all these challenges, and make our readers aware of the complexity of the custom products.

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