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But what is the Fourier Transform? A visual introduction.

A 20-minute video by 3Blue1Brown about transforms and signals, on the Mathematics shelf. It came up in 3 Reddit threads, in r/ElectricalEngineering and r/3Blue1Brown. It is pitched at introductory level.

3Blue1Brown, Video, 20 min, 2018, on the Mathematics shelf

An animated introduction to the Fourier Transform.

Study notes

Introductory, Visual intuition. Step 8 of 13 in The mathematics of change and signals

Helpful first

• Sine waves
• Basic idea of an integral

What it builds

• Decompose a sound into frequency components.
• Wind a signal around a circle at different frequencies.
• Use the centre of mass to detect matching frequencies.

Useful moments

• 0:27Decomposing frequencies from sound
• 3:47Winding a signal around a circle
• 4:49Building a frequency-unmixing machine

Check yourself: Why does testing a matching frequency produce a different result from testing a mismatched one?

Next in the path: But what is a Fourier series? From heat flow to drawing with circles | DE4

Notes are based on metadata, Reddit context and selected English caption passages. They are not a review of every claim in the video.