The wave artifacts phenomenon is from uneven imaging on the media. This is more noticeable in low relative humidity conditions (less than 15%RH). Experimentally, these phenomena are caused by the developer roller surface condition and the chargeblade condition. These are the two critical components for correct toner development. The function of the developer roller is toner tribo-charging and to supply charged toner to the photoreceptor for image development. The developer roller requires the correct surface roughness and electrical resistance. Low surface roughness of the developer roller causes the wave image. Also, the chargeblade force contributes to this phenomenon.
Tadahiro Kaneko, "Wave Image Artifacts in Monocomponent Development System" in Proc. IS&T Int'l Conf. on Digital Printing Technologies (NIP15), 1999, pp 594 - 597, https://doi.org/10.2352/ISSN.2169-4451.1999.15.1.art00055_2