He was in the middle of his third attempt at deliberately combining Noise Suppression and Acoustic Mapping when someone knocked on his door.
The combination wasn't working the way he wanted it to. The theory was sound enough, both skills operated in the same sensory register, one dampening sound output and one reading sound input, and they should have been talking to each other the way Cartographer's Eye and Surface Reading talked to each other. But deliberate synthesis was proving harder than the accidental version. The understanding that had arrived on the wet street had come from necessity and momentum, from a fight happening around him with no time to be analytical about it. Sitting cross-legged on his apartment floor, trying to think his way into the same state was producing nothing
