I’ve heard clips of hot water being poured vs cold water, and if you heard the examples, you would probably guess right too.

Time of day seems almost easy. Are there animals noises? Those won’t sound the same all day. And traffic too. Even things like the sound of wind may generally be different in the morning vs night.

This is not to suggest the researchers are not leaking data, or that the examples were cherry picked, it seems probable they are doing one or the other. But it is to say, if you were trained on a particular intersection, and heard a sample from it, you could probably train a model to predict time of day reasonably well.