I imagine it would be like if there were Rosetta Stones of text, written with a language you could read and a language you couldn't. For your purposes, discarding the text you can't read would be fine and you wouldn't lose anything. But if you were ingesting a bunch into an LLM, the additional text would give the LLM more context and help it make connections and relate words more accurately, even if you never were going to have it output anything in the language you don't understand.

The inaudible sounds add context and additional datapoints on how the audible sounds are related.