The Cape4all, Multi-Channel Sound for Hearing Aid Research with BeagleBone

Alasdair Allan
2 min readAug 13, 2018


There’s an increasing amount of work being done in medical research using open hardware. One obvious example of that is of the OpenAPS project, where people with Type 1 diabetes have stopped waiting for official FDA approval and are now building their own overnight closed loop Artificial Pancreas Systems.

However there are others that don’t get quite as much press, and the Cape4all is an interesting open hardware project to build a multi-microphone audio extension cape for the BeagleBone Black. Along with the openMHA hearing aid research software, the cape can be use to perform hearing aid signal processing in real-time.

The Cape4all with two hearing aids connected. (📷: Herzke et al.)

“Part of the work in hearing aid research is to develop novel signal processing algorithms that can be used in hearing aids… Running an algorithm under test on an end-user hearing device is practically infeasible as it requires access to a proprietary system of a hearing aid manufacturer, and a large effort for the down-to-hardware implementation is required on such devices.”

Top down view of the Cape4all. (📷: HörTech gGmbH)

The Cape4all was presented back in June at the Linux Audio Conference in Berlin, Germany. You can find more information as part of their research paper, while the Cape4all hardware design files — including the cape schematic and board layout files, along with the needed ALSA kernel drivers — are also available on the project’s GitHub repo.