20. Harmonics

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Harmonics

ND320 C4 L1 18 Harmonics

Harmonics recap

Summary

Real periodic signals are rarely sinusoidal. Still, we like to use the Fourier transform to learn about the periodicity of these signals. All periodic signals are composed of a fundamental frequency, which is the lowest frequency of the periodic signal, and integer multiples of this frequency called harmonics. In this lesson, we see this for ourselves and how the fundamental frequency relates to the signal in time-domain.

Notebook Review

If you wanted to interact with the notebook in the video, you can access it here in the repo /intro-to-dsp/walkthroughs/harmonics/ or in the workspace below.

Code

If you need a code on the https://github.com/udacity.

Harmonics Quiz

An FFT reveals that a signal is comprised of the following frequency components (all in Hz):

[1.5, 2.1, 3.0, 4.3, 4.5, 6.0, 6.3]

What fundamental frequencies are present in this signal?
SOLUTION: 1.5 Hz and 2.1 Hz

Harmonics Further Research

Further Resources

Harmonics explain why different instruments sound different despite playing the same note. Check out 12tone's video on Why Don't All Instruments Sound The Same? for a more in-depth explanation.
You can also watch 3Blue1Brown's video Music And Measure Theory explaining why certain notes sound good together by looking at multiples of their frequencies.

New Vocabulary

  • Harmonics: the fundamental frequency and integer multiples of the fundamental frequency of periodic signals.

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