What it is
Singing Power Ratio. The ratio of energy in the 2–4 kHz band (the “metal core” band) to the overall spectral energy.
It is the source of a voice’s carrying power — an orchestra’s energy sits below 1 kHz, so a peak at 2–4 kHz lets the voice cut through the orchestra and reach the audience.
Where it comes from
After the FFT, compute the dB difference between the 2–4 kHz peak energy and a mid-low-frequency reference. The Singer’s Formant monitor draws this curve in real time.
How to read it
High SPR = a metal core that carries and stays clear at a distance; low SPR = a voice that sounds big up close and vanishes far away.
In Phonation Balance it is the main reading of the “ring” end; in Dynamic Balance it serves as the vertical axis — as volume changes, SPR should not jump along with it.
Where it is used
Phonation Balance — Shared edge · used here for ring: whether the 2–4 kHz metal core is present and strong enough.
Dynamic Balance — Shared edge · used here as the brightness axis: SPR should not jump as volume sweeps soft to loud.