H1 & H2: Two Peaks on the Spectral Lines
H1 is the strength of the first harmonic, H2 the second. The height difference between them hides the secret of vocal fold thickness.
The height of a spectral line = how strong that harmonic is. Let's single out H1 (at F0) and H2 (at 2×F0): strong H1 → round, thick waveform (like male voices and chest voice); strong H2 → sharp, bright waveform (like female voices and head voice). On the spectrum it simply comes down to which of the two lines is taller.
Experiment 7 · Drag the H1/H2 Heights
Drag the heights of the two spectral lines (or use the sliders below) and watch the waveform change shape. Try raising H1 while lowering H2, then the reverse — the "thick/thin" feel of the sound changes accordingly.
H1 and H2 are two neighboring lines on the spectrum. They are not just any two lines — their "height difference" is a dedicated acoustic metric, coming up in the next chapter.