A standard, low-cost protocol for measuring and reporting the audible noise of wearable robots (prostheses, exoskeletons, orthoses).
Users care about how loud their devices are, but there have been many different approaches to measuring sound, so published numbers can't be compared directly. UESL is the A-weighted equivalent continuous sound level (Leq,A) measured at the user's ear, during real use. You need a Class 2 sound level meter, a quiet room, and 9 trials.
📋 Read the full protocol checklist → · 🖨️ Printable PDF
- Mic at the ear: Class 2 SLM (A-weighted, FAST 125 ms, ≥ 8 Hz) at the back of the head, or a binaural headset.
- Quiet, absorptive room: ambient < 35 dBA or ≥ 6 dB below the device; carpet or mat.
- Each trial: 10 s ambient (still & silent), then 20 s of steady-state use.
- 9 trials: 3 slow · 3 normal · 3 fast self-selected speeds.
- Energy-average each trial to Leq; subtract ambient if within 6 dB.
- Report mean ± SD over all trials & users, n trials, user mass/height, and device settings.
| Device | Category | UESL (dBA) | SD (dBA) | Trials |
|---|---|---|---|---|
| No device | baseline | 35.5 | 2.3 | 72 |
| VSO – off | passive | 37.4 | 3.0 | 72 |
| MBLUE ankle exoskeleton | powered | 37.6 | 2.7 | 72 |
| Proteor Kinnex 2.0 | quasi-passive | 38.2 | 3.4 | 54 |
| Fillauer AllPro | passive | 38.6 | 2.6 | 18 |
| Ottobock Genium X4 | quasi-passive | 40.1 | 2.0 | 18 |
| Nylon pants | baseline | 41.5 | 2.8 | 72 |
| Ottobock Empower | powered | 43.6 | 2.3 | 18 |
| VSO – on | quasi-passive | 43.9 | 1.7 | 72 |
| DESR VSO | passive | 44.0 | 3.0 | 72 |
| Dephy Sidekick | powered | 44.6 | 3.4 | 72 |
| Open-Source Leg v2 – ankle | powered | 47.7 | 4.4 | 54 |
| Össur Power Knee | powered | 49.5 | 2.6 | 36 |
| Open-Source Leg v2 – knee + ankle | powered | 50.6 | 2.2 | 18 |
7 participants (4 able-bodied, 2 transtibial, 1 transfemoral). Machine-readable version: benchmarks.csv.
Preliminary design targets: in our (small, N = 7) cohort, the sound of a device began to have a moderate impact on users' willingness to wear it daily at ≈ 44.4 dBA UESL, 12.5 sone loudness (N5), and 1.95 acum sharpness (S10).
Measured a device with this protocol? Please share it. Open an issue or pull request with a filled-in row of reporting_template.csv so the benchmark can grow.
Paper in preparation. Until it's published, please cite this repository (see CITATION.cff or the "Cite this repository" button on GitHub):
Z. Bons, S. Thiede, and E. J. Rouse, "Sound Matters: Standardizing Audible Noise Reporting for Wearable Robots," in preparation.
Zachary Bons · zbons@umich.edu · Neurobionics Lab, University of Michigan Supported by the NSF Graduate Research Fellowship Program (DGE-2241144).
See CHANGELOG.md for protocol version history.