We did noise test with several feet (average db value during 1 minute with Fairphone 3+):
- squash balls feet: 30.7db
- elastomer feet diameter 20mm / height 20mm: 30.5db
- elastomer feet diameter 20mm / height 25mm: 30.1db
- elastomer feet diameter 25mm / height 30mm: 31.5 db
Video: https://youtu.be/ComPi0pY-wg