I have a challenge for you all

The shadowlight challenge
1. find an old oil-based radiator, or a fence, or a grid that produces linear shadows
2. create an area where light is weak due to lack of coherence
3. attempt to hear the shadow by measuring the audible variance in friction where light is strong vs weak
4. good luck! I used a brush on carpet but my ears are not QUITE ready for that level of detail?