The Tyranids can effect psychically and Electro-magnetically.

• Devastation of Baal:

"We are attempting to boost our vox gain to break through the tyranid jamming field, but their methods have become more sophisticated since we last fought them,’ said Incarael. ‘They seem to know which frequencies to shut down as soon as we open them up. Only brute force will overcome it, but when we push, they push back harder. Our capacity to overcome their denial broadcast is lessening. They make a priority of our vox and augur arrays."

• Shield of Baal [Exterminatus]:

"The defenders tried to pierce the poison fog with their augurs, but it was if the world ended at its edge. Tiny organisms drifted amongst the mists, their microscopic spines transmitting a wall of electro-magnetic noise, proof against the probing technology."