A small absence. A complete perception.
A harmonic sound can contain frequency components at whole-number multiples of a fundamental: f₀, 2f₀, 3f₀, and so on.
Remove f₀ while keeping enough of those harmonics, and a listener can still perceive a pitch corresponding to f₀. This is the missing fundamental, also known as virtual pitch or residue pitch. The perceived pitch does not require energy at that frequency in the original sound.
Why the name fits
For us, this is a useful image for research: understanding the structure of a problem can matter as much as adding more to it.
It is an inspiration for the lab’s approach, rather than a claim about how Rivet works. Our models still need to earn their results through measurement and listening.
The waveform on our homepage
The diagram combines sine waves at 400, 600, 800, 1,000, and 1,200 Hz. These are harmonics two through six of a 200 Hz fundamental. Each harmonic has a different starting phase and an amplitude proportional to the reciprocal of its harmonic number.
A slowly varying amplitude envelope shapes the signal. This introduces nearby frequencies around the retained harmonics without adding a 200 Hz component. The diagram shows 200 milliseconds of this synthetic signal; it is an illustration, not an output from Rivet.