Basically the story was how in the future consciousness is transported from system to system by series of relays, and one man who went the furthest/spent the most time out of body came back to find that he saw sound and could hear light. At first he was terrified, but began to embrace it, even prefer it over normal sensation. After being told by all his colleagues that it could be fixable, he refuses and keeps his new forms of sensation. It was a Soviet era short story that may have been titled something akin to “mixed up”, but every search with that title comes up with nothing.
Looking for Soviet era sci-fi short story about a man's sight and hearing being switched
The crossover of stimuli from one sense to another is called synaesthesia or synesthesia. Lists of works are given in Wikipedia's "Synesthesia in fiction" and "Synesthesia in literature"; is your story there?– Invisible TrihedronMay 12, 2020 at 14:29
This sounds like "Mixed Up", a short story by the Ukrainian sci-fi writer Vladimir Savchenko. I read it in a compilation of Soviet science fiction short stories called Red Star Tales.
A synopsis is available here:
When an alien race beamed their personalities across space to Earth, mankind learned the secret of interstellar travel; not everyone, however, was able to sustain the transfer, as evidence by the death of several so-called psychonauts. When M. A. Kolotilin returns from his beamed journey, his eyes sense sound while his ears register color. Initially perplexed by this mental cross-wiring, he soon begins to accept and adapt to the uniqueness of his state even while his wife leaves him and his fellow scientists urge treatment and experimentation.