Where is Portal 2's excursion funnel sound?

Where is Portal 2's excursion funnel sound? - Back view of unrecognizable man walking towards ancient monument Great Sphinx of Giza

I am looking for Portal 2's excursion funnel sounds. Where could I find them? I need them (if multiple) for a little project I am making. I already used the steps from this post and I cannot seem to find what I need. I just got bumped into some strange HL2(?) sounds.

portal-2

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Where is Portal 2's excursion funnel sound? - Back view of anonymous female traveler standing near ancient wall with Egyptian engraving

Where is Portal 2's excursion funnel sound? - Man in Blue Jacket Walking on Pathway

Where is Portal 2's excursion funnel sound? - Black Crossover Car Standing Off Road

Portal 2 - Full Walkthrough

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