ToneWood · Measurement guide
What affects a wood tap-tone measurement?
Check geometry, mode selection, holding position, microphone recording and repeatability before comparing tonewood measurements.
Start with geometry and units
A calculated acoustic property depends on more than the recorded frequency. Mass and volume determine density, and dimensions enter the vibration model. A thickness error, swapped axes or an incorrect shape choice can change a result even when the recording sounds clean.
Measure the dimensions requested for the actual geometry. A wedge-shaped blank should not be treated as a uniform rectangular bar, and a carved violin plate should not be treated as an uncarved blank. Check millimetres versus metres and grams versus kilograms before investigating the microphone.
A peak is not a mode label
Holding and striking positions change which vibrations are excited and recorded. Multiple resonances, background tones or two nearby modes may compete. Follow the app’s geometry-specific guide and review the spectrum rather than selecting a peak solely because it is the largest.
Avoid importing a node position from a different experiment. The app’s illustrated 0.224L grip and a carved-plate Mode 5 nodal line describe different vibration models.
Inspect the recording and decay
Clipping, sustained background noise, microphone obstruction, touching the blank and overlapping taps can spoil the usable signal. Use a short, gentle strike and leave enough time between taps. Keep the phone position and recording setup consistent between sessions.
Frequency and damping require different evidence. A visible FFT peak does not automatically provide a reliable decay-based quality factor Q. Compare Q only when the selected mode, decay method and signal quality are comparable.
Separate repeatability from accuracy
Repeat the same setup, then reposition the blank and repeat again. Keep the individual recordings and note what changed. A stable result under one setup can still share the same geometry or model error across every repetition.
For comparisons, group similar geometry and material directions and record conditions. Do not report a universal accuracy percentage from a few taps. Use a reference method and enough controlled samples to quantify the uncertainty for a defined scope.
A short checklist before saving
- Geometry, grain direction, dimensions, mass and input units match the sample.
- The microphone is clear, the recording is not clipped and taps do not overlap.
- The selected resonance is consistent across repeated sessions.
- Damping evidence and environmental notes are retained with the record.