Fretting-force model
This calculator estimates static restoring force for an ideal string displaced by h at mid-span: F ≈ 4Th/L under small-angle, constant-tension assumptions. Real fretting also involves fret position, original action, stretch-induced tension changes, friction and finger contact. The result is not measured barre force. Tension input is kgf (kilogram-force): 1 kgf = 9.80665 N. A kg is a mass unit, not a force unit.
Plucking and harmonics
Plucking sets an initial displacement. After release, the string undergoes mainly freely decaying vibration; sustained driving is forced vibration. An ideal linear model decomposes motion into modes, whose amplitudes and phases depend on pluck position. The tools below illustrate this relationship. Integer frequencies represent an ideal flexible string. The pluck baseline comes from triangular initial displacement: aₙ = 2y₀sin(nπb)/[π²n²b(1−b)], where b is pluck position divided by length. Its sign is represented by phase 0 or π. Material and plucking-object presets add illustrative spectral filters, not measured damping or material constants. Audio does not model time-dependent free decay or a complete guitar body.
Buzz and fret adjustment
Buzz can result from low action, uneven frets, unsuitable neck relief or nut slots, or strong plucking. Remedies depend on diagnosis and need not simply raise action. PLEK scans geometry under actual or simulated string tension and assists fret and nut processing. An operator still sets targets for the strings and playing style, followed by inspection and play testing; no setup guarantees freedom from buzz at every playing force.
Text version of this page
Kepma Total Fretting Force Model and Calculator
Kepma Total Fretting Force Model and Calculator
1. Physical principles and model
A barre across all strings must overcome their restoring force from tension. This calculator estimates the total force using a simplified physical model.
2. Animated demonstration
The animation simulates a finger pressing the strings in a barre. Click the button to watch:
3. Interactive calculator
Enter your guitar's parameters to calculate the estimated force for a barre across all strings.
Total fretting force vs. action
Kepma String Vibration Visualisation and Sound Synthesis
Kepma String Vibration Visualisation and Sound Synthesis
- Harmonic number
- Frequency (Hz)
- Amplitude
- Phase (π)
- Relative level (dB)
Parameters and principles
A string's complex vibration can be expressed as a linear sum of simple normal modes (harmonics), each with its own frequency, amplitude and phase.
- y(x, t): instantaneous string displacement at position x and time t .
- An: harmonic n amplitude.
- sin(nπx/L): spatial term describing the standing wave (L is the string length).
- fn: harmonic n frequency (fn = n · f1)。
- φn: harmonic n phase.
Physical parameters and tone
In simulated plucking mode, the amplitude An depends on several physical factors to model tone formation more realistically:
- P(n, b): plucking position factor.P(n, b) = |sin(n · π · b)| This determines which harmonics are excited at b . Plucking at a harmonic's node suppresses that harmonic.
- E(n, object): excitation factor, set by the hardness of the plucking object. A hard pick excites more high harmonics for a brighter tone; a soft fingertip reduces them for a warmer tone.
- D(n, material): damping factor, determined by the string material. Steel retains more high harmonics and sounds crisp; nylon damps them faster for a softer tone.
Audio controls
Global controls
Control mode
Kepma String Vibration Visualization and Sound Synthesis Tools：视频内容
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