Q Factor (Quality Factor) measures how sharp and selective a resonance is β how precisely a system locks onto one specific frequency and resists energy loss to adjacent frequencies.
The formula is simple: Q = fβ / Ξf β the resonant frequency divided by the bandwidth at the β3dB point (where peak amplitude drops to 70.7% of its maximum).
How to read Q values:
Why it matters for resonance research: A higher Q means your prototype is storing more energy per cycle relative to what it loses. A Q that increases as you adjust geometry or coupling is a direct measurement of your device becoming a more efficient resonator. Tracking Q across experiments reveals whether your design changes are moving toward or away from true resonance.
Use β‘ Auto-fill from peaks to populate fβ automatically from your strongest detected peak, then click βΏ Estimate Ξf to measure the bandwidth directly from your FFT data.
PSD (Power Spectral Density) shows how the power of your signal is distributed across frequencies β not as sharp peaks, but as a continuous density curve. It answers the question: does this signal have more energy at low frequencies, or is it spread evenly?
The spectral slope B tells you the shape of the PSD curve on a log-log chart β how steeply power drops as frequency increases:
Fractal Dimension D is calculated from B as: D = (5 + B) / 2. It describes the self-similarity and complexity of your signal across scales.
- D β 1.5 β white noise. Completely random, no fractal structure.
- D β 1.0 β pink noise. Found in heartbeats, music, natural systems. Scale-invariant.
- D between 1.0β1.5 β your signal has fractal character. It repeats its pattern at multiple scales simultaneously.
RΒ² Fit Quality tells you how reliably the slope B was measured. Above 0.9 is excellent β the power law fits cleanly. Below 0.7 means the slope is not consistent across the selected range and the result should be interpreted with caution.
| Harmonic | Freq (Hz) | Amplitude | Even/Odd | Ο Aligned | Schumann |
|---|---|---|---|---|---|
| β run analysis first β | |||||
THD+N (Total Harmonic Distortion + Noise) measures how much of your signal's total energy is not in the fundamental frequency β it captures all harmonics plus background noise as a single percentage or dB value.
How to read the values:
- THD+N % β percentage of total signal power that is harmonic distortion + noise. Lower = purer signal. Below 1% is excellent for most applications.
- THD+N dBc β same measurement in decibels relative to the fundamental. More negative = purer. β40 dBc means harmonics are 100Γ weaker than the fundamental.
- SFDR (Spurious-Free Dynamic Range) β gap in dB between your fundamental and the strongest unwanted peak. Larger is better. It tells you how much headroom you have before interference becomes a problem.
- Tone Character (Even/Odd ratio) β even harmonics (2nd, 4th) give a warm, musical sound. Odd harmonics (3rd, 5th) give a harsher, more distorted character. This ratio tells you the harmonic personality of your signal.
In resonance research, unexpectedly low THD at a specific geometry or frequency is a meaningful signal β it suggests the system has found a natural, efficient mode. High SFDR means your fundamental dominates cleanly with minimal interference.