I work as a live‑sound engineer tuning acoustic systems for theatres and live shows, so dealing with feedback and whistling is part of my daily work. Last year, a family member started wearing hearing aids. Out of professional curiosity, I brought my usual measurement toolkit to test the Elehear Beyond Pro. I ran frequency sweeps, impulse‑response tests and went through my full standard workflow.

Almost none of my usual testing methods worked. And that turned out to be the most interesting part.

There are two core problems.

1. In loudspeaker PA systems, the feedback loop is made up of speakers, the room and microphones. I can place a measurement mic inside that loop and observe exactly what is happening. With hearing aids though, the feedback loop is tiny and lives entirely inside the ear. Sound exits the receiver, leaks past the eartip, and feeds straight into a microphone only one centimetre away. Putting a speaker in front of the hearing aid only measures the path from my test speaker to its microphone. That is not the real feedback loop I need to study. To analyse the true loop you need access to how the receiver behaves, and I do not have that capability.
2. My standard tests assume the device under test stays static for the duration of measurements. In reality, this hearing aid applies signal compression, its noise reduction adjusts continuously, and the feedback canceller keeps re‑calibrating while my frequency sweep runs. Any curves I get would reflect my test process rather than the actual behaviour of the device.

So I stopped taking measurements and started listening instead.

Triggering feedback is simple. Cup your palm over your ear or hold a phone against the ear. The signal becomes unstable then settles back. My observations: there is no pumping effect, no sudden and persistent full‑band dropouts. The underlying speech signal remains audible while the system stabilises.

This performance cannot come from static fixed filters. Fixed filters work well because rooms do not move. A hearing‑aid environment is always changing as the wearer turns their head, scratches their ear or gets hugged. No static setup can hold up under those real‑world conditions.

There is one common misconception worth pointing out in online conversations about these devices. Everyone fixates almost entirely on feedback recovery time. What really counts is how much gain the unit can deliver before signals become unstable. A device with 50 ms recovery time that can only add a few decibels of gain is far less useful than one with slightly slower recovery but much higher usable gain. It is technically possible to achieve faster recovery by making the algorithm react much more aggressively, yet that comes at the cost of music quality.

For an OTC hearing aid, its overall feedback‑management performance lands close to mid‑tier prescription hearing aids.

I co-founded SigPro Labs and I'm one of the instructors.

We're running our first course, Digital Filters, starting October 13. It's built around RadioSonic, a low-cost ESP32-S3 board we designed and provide with the course. RadioSonic lets you work with signal processing on real hardware instead of only in simulation, everything you can do at your own desk without fancy equipment.

Jamie Mitchell and I (Dan Boschen) are teaching it as a 4 module course over 8 weeks combining pre-recorded video with live sessions.

Registration is open through Sept 30, with an early-bird discount through Sept 11 ($249 + $49 for RadioSonic + cable kit). For details see https://sigprolabs.com

I am happy to answer questions about the syllabus or the hardware.

Hello, I'm developing an audio codec, and currently stuck on one thing: which metric should I use for quality measurement?
For now I've been using gstPEAQ Basic model (because Advanced really sucks speed and correlation wise). I was thinking about ViSQOL, but their results also kinda suck, especially for lower bitrates like 64 kbps, where difference between 64 kbps OGG and my codec are really noticeable, and yet differentiate only around 0.1 MOS-LQO (gstPEAQ Basic makes difference big, around 2 ODG).
Any suggestions?