Great now you tell me. Anyway.
So 3 mm White LEDs light sources those are characterized by temperature
in Kelvins.
Warm white(2600K to 3700 K ), neutral white (3700k to 5000 K ) & cool white (5000K to 8300 K) + Diffuser, which is your laser cut lightguide pattern of 45°
angle of incidence reflecting prism surface,typical in light guide designs (Top) + Your 3mm thick Light Guide Plate which is more than likely a (PET) or
Polyethylene terephthalate substrate (Middle) + White reflector which goes by the manufacture name of Decotex.
A canvas or Sheer white Voile Transparent Window Panel Curtain Drape. Which would be transparent to audio frequencies (Bottom layer).
Yeah! It is very ambitious and creative. I would go with the thousand grit sandpaper make sure not to deform the shape of the LEDs themselves…and your panels backwards turn it around .