A Noise Canceller is a device created by Kokonoe that allows the usage of the Azure Grimoire while under the effects of seithr nullification. It was built specially for Ragna the Bloodedge.
At the end of the Continuum Shift that occurred in January, 2200AD, Kokonoe installed this into an artificial left arm that she fashioned for Ragna. However, it was not active, and she instead waited for when she had him close with Celica A. Mercury. When the two were finally close to one another, she lied to the Grim Reaper, telling him that she had instead installed a Multi-Dimension Bomb within him, forcing Celica and Ragna to stay close. This gave Kokonoe enough time to synchronize the wavelengths between Celica's seithr nullification ability and the Noise Canceller.
Kokonoe activated the Canceller after she acquired enough data, allowing Ragna to use the Grimoire in Celica's presence. This ability also extended to when the Kushinada's Lynchpin was activated, meaning that Ragna could activate the Azure Grimoire and use Ars Magus even in a world devoid of seithr. Even within the Embryo, the Canceller still worked.