Behind the scenes of competitive hearing aid comparisons- Detectives in research audiology

As a hearing aid researcher, I am often asked about my favorite studies we’ve completed at the Phonak Audiology Research Center (PARC). Although I try to love all my projects equally, my true answer would be competitive hearing aid comparisons. I find it fascinating to look ‘under the hood’ of the hearing aids from various manufacturers. When studying Phonak devices, we have research tools and research software, which makes understanding how our hearing aids ‘think’ relatively straight-forward. Hearing aids from other manufacturers, however, are essentially ‘black boxes’. As we study these competitive products, we are detectives putting the pieces together. Each manufacturer has made decisions— areas of innovation in which they’ve specifically invested time and energy.

As we study hearing aids from various manufacturers, certain patterns stand out. It becomes clear what manufacturers have invested time and energy into connectivity, versus perhaps sound quality or performance aspects of hearing. At the Phonak Audiology Research Center, we realize that the most effective hearing instruments are the ones that provide connectivity, sound quality, AND performance. Yes, certain manufacturers may ‘excel’ in one of these areas, but hearing aid users don’t ‘live’ in one type of listening environment. More than ever, seamless, effortless listening is key.

Our priorities at PARC

The first question I am asked when speaking about competitive comparisons is, “Well, aren’t you biased towards Phonak devices?” My answer is, “What good would that do us?” On the contrary, it’s a priority at PARC to gather unbiased opinions of hearing instruments. This means programming all hearing aids the same way, with the same coupling, same hearing loss — keeping as many aspects equivalent as possible. To further eliminate bias, we’ll often do listening comparisons that are blinded so we don’t know which manufacturer is which when determining who is ‘best’. For example, you’ll frequently hear the researchers at PARC asking each other, “Can you listen to this and tell me which one you think is best? I won’t tell you which manufacturer is which.” Spend too much time around PARC, and you will inevitably be roped into an impromptu, blinded listening test.

So how do we typically assess three key areas of hearing performance across competitors?

Performance (Listening in complex environments): An essential aspect to hearing aid performance, listening in background noise, is a common area of investigation for us at PARC. We have several, specialized research tools that were developed by our research colleagues in Switzerland, specifically designed to provide objective measures of hearing aid performance. Signal-to-Noise Ratio Analysis, for example, is performed by putting each manufacturer’s devices on KEMAR (our acoustic mannequin) and comparing the ‘input’ SNR delivered through an array of sound field speakers to the SNR at the output of the hearing aids to determine hearing aid benefit. This, along with listening to the hearing aids while in complex scenes, give us a great idea of how each hearing aid performs in complex environments.

Sound quality: We have found that the best way to assess sound quality is through a very sophisticated research tool: Listening. Significant differences now exist between manufacturers in the ‘fullness’ and ’naturalness’ of sound. Although some aspects of sound quality may be hardware-related, much of it also has to do with the frequency shape each manufacturer has chosen. Some emphasize high frequencies, mid-frequencies, or low frequencies. We always include media and movies that span a variety of genres, with priorities shifting between music, sound effects, and dialogue. Does the hearing aid sound like it came out of a plastic toy radio that a three-year old would own, or does it sound like you’re in an actual orchestral hall? Recordings from the hearing aids are used in blinded listening tests (“Hearing is Believing”) that help us understand the sound quality preferences of large groups of listeners.

Connectivity: In addition to technical specifications related to connectivity, we have found key differences in the functional range, ease of connectivity, streaming sound quality, and consistency of the streamed signal. Testing these solutions from various distances between streamer and hearing aids, and recording the streaming sound quality, has revealed notable artifact, ’warbling’, dropouts, and other distracting sounds that accompany the intended signal.

So together, these three aspects of hearing comprise the foundation of our competitive comparisons. Filling in these gaps and gathering clues is certainly a challenge, but make our jobs interesting and exciting.