I cannot offer you references you seek, I am not aware that any exist in the form you seem to be looking for however, I have been wearing specs with helmets for over 17 years now. My experience is: I have not noticed or detected any effect upon noise attenuation. I use bifocals but have tried the varifocal which are completely useless. Even with the modern wide focal parameters offered by pentax, they reduce your peripheral vision by a considerable amount. As for Sunglasses, well I suppose its personal preference and circumstances. Sometimes I do, sometimes I do not. If I am into sun on a cloudless day then I do and have the tinted visor down as well its very calming. My advice is to go for titanium frames. I have discovered that constant on/off with the specs [not sensible to don helmet with then on] does reduce the frame life dramatically. HTH