The Noise (ノイズ) are an unknown race that has appeared throughout series' times.
13 Years ago at the United Nations General Assembly, the Noise were officially recognized under the classification of "special disaster." The Noise have been observed to take form in various shapes and sizes, but all of them are equipped with a means of attack. Each form shares certain attributes specific for the purpose of functioning as a weapon: They only target human beings. Any person who comes in direct contact with them immediately turns into carbon and dissolves, as does the Noise itself. The general laws of nature regarding energy loss and consumption do not apply to them.
They typically appear without warning, leaking out of thin air and multiplying instantly. There are no valid means of repelling their attacks. Aside from sacrificing an equal number of human bodies that would reduce the Noise to lumps of carbon, the only other option is to wait and stall for a period of time after their emergence, until the Noise self-destruct on their own. Because they look similar to other living creatures, past experiments had attempted to communicate with them, but these were unable to proceed due to numerous failures. Ultimately, communicating and controlling the Noise is impossible because they likely have no capacity for free thought. This is the data that has been recorded thus far. Because there are still many mysteries surrounding the Noise, all the nations of the world are currently working on further research in order to gain a better understanding of them.
Enormous quantities of Noise exist within the Treasury of Babylonia, an extradimensional space from which they can be drawn forth and controlled using the complete relic Solomon's Cane. It is unknown if this is their home dimension.
In Episode 13, Finé reveals that humans created Noise to fight against each other once the Curse of Balal separated their languages and sparked widespread war.
The Alca-Noise (アルカ・ノイズ) is a variation of Noise, created by alchemy. Unlike common Noise, they have the ability to destroy Symphogear, making them more dangerous than common Noise. The parts that can destroy Symphogear are the parts that are glowing with green light located at the center of their frontal body. However, unlike regular Noise, they can be destroyed by means other than Symphogear, such as firearms. Their name is derived from Alkahest.
Karma Noise (カルマノイズ) are another variants of Noise. Karma Noise are Noise from a parallel Earth. They first appear during the Zwei Wing concert, where Tsubasa Kazanari sacrifices herself by singing her superb song to destroy them.
They only appear in places with high concentration of humanity or Phonic Gain. A single Karma Noise is powerful enough to kill several people at once. But their greatest threat comes from disintegrating people without they themselves disintegrating. Also their ability to dematerialize and rematerialize themselves makes them harder to catch. For all their toughness however, Karma Noise will eventually disappear if there are no people around to target. Essentially, Karma Noise are an automated weapon designed to kill, vanish, appear and kill again in a cycle.
Musha Noise (武者ノイズ) are Noise that absorbed shattered fragments of the relic named Muramasa, a cursed/possessed legendary Japanese sword, sometime after high ranking power hungry Japanese officials attempted to activate the relic and failed.Its ability to induce bad lucks is apparent in the Musha Noise, making them fearsome foes.
- Their ability to not be affected by conventional weapons due to the effects of their Phase Contrast Barrier, and yet remain able to affect the world around them, is similar to that of the Gnosis from Xenosaga.
- Another similarity is that just like the Noise, the Gnosis have the ability to kill people by transmuting their bodies into another substance (salt for the Gnosis, carbon for the Noise) just by touching them.
- Also like the Noise, mythical creatures such as fairies and other creatures said to be of the imagination were most likely the Gnosis.