Challenge 2: Maximum-Strength Noise Reduction Damaging the Voice — Solution Walkthrough

The answer:

The warbly, "underwater" quality is exactly the artifact this
chapter's own warning box describes as the risk of pushing noise
reduction too aggressively. At maximum strength, the tool isn't just
removing the sampled background noise — it starts distorting parts of
the actual voice that happen to resemble that noise fingerprint,
especially quieter or breathier moments where the voice and the noise
profile are closer together in character.

Why "maximum, just to be safe" is the wrong instinct here:

More noise reduction isn't automatically safer or better — it trades
one problem (audible background noise) for a different, often more
noticeable one (a distorted, artificial-sounding voice). A recording
with a faint trace of noise left in usually sounds more natural and
listenable than one that's been aggressively processed to remove
every trace of it.

What to do instead:

Dial the strength back to a moderate setting that meaningfully reduces
the background noise without introducing the warbly artifact, even if
a very faint trace of the original noise remains audible.

WHY THIS WORKS AS AN ANSWER
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This exercise checks that "more noise reduction" is correctly
understood as a trade-off, not a strictly better setting, and that a
moderate setting is the right fix rather than pushing even harder.