Challenge 1: Normalizing Before Noise Reduction — Solution Walkthrough

The answer:

Normalizing first raises the recording's overall volume to hit a
target level — but normalization can't tell the difference between
the wanted voice signal and the unwanted background hum. It reads the
waveform as a whole and raises everything in it together, so the hum
gets amplified right along with the voice.

Why applying noise reduction afterward didn't fully fix it:

By the time noise reduction ran, the hum was already boosted to a
louder level than it started at. The noise profile still gets sampled
and applied correctly, but it's now removing a louder version of the
same noise, which is a less clean result than removing the noise
before it was ever amplified in the first place.

What should have happened instead:

Per this chapter's own ordering, noise reduction should run first, on
the original, unboosted recording — removing the hum while it's still
at its original, lower level — and normalization should come last, so
the target volume is being set based on the already-cleaned signal.

WHY THIS WORKS AS AN ANSWER
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This exercise checks that the reason order matters is correctly
traced back to normalization amplifying noise and signal equally,
confirming why noise reduction has to happen first.