Chladni Resonance Lab — Sound into Patterns

What this does

Chladni Resonance Lab simulates sand accumulating in relatively quiet regions of a vibrating plate. The animation begins with scattered grains; as the model evolves, they drift, scatter and settle into visible nodal structures. Change a resonance, excitation position or plate model and watch the existing grains reorganise rather than jump to a newly drawn figure.

Key features:

• Native Praat Demo visualisation; no Python or external graphics engine.
• Individual sand-grain motion, progressive settling and continuity across parameter changes.
• Two idealised plate models, frequency-selective modal excitation and adjustable excitation position.
• Ten defined presets, including dual-mode interference, mode sweeps and multi-tone excitation.
• Optional Sound analysis with resonance-based and explicitly artistic spectral mapping.
• Three graphical quality settings, optional nodal overlay and vibration-field display.

Quick start

1. Run Chladni_Resonance_Lab.praat from Praat. A selected mono or stereo Sound is optional.
2. Choose Quality: Balanced is a practical starting point.
3. Choose a Start preset; try Fundamental Resonance to observe simple node formation or Modal Morphing to see continuous reorganisation.
4. If a Sound is selected, choose Sound mapping: Resonance-based excitation or Creative spectral mapping.
5. Leave Plate lowest resonance Hz at 0 for automatic/default tuning, or enter a positive reference frequency.
6. Use Start / Pause or Space. Explore the frequency and plate controls as grains settle.
7. Click the plate to move the exciter; click the frequency/response strip in Explore mode to retune the drive.

Diagnostic self-test runs numerical checks instead of opening the visual demonstration; leave it disabled for normal use.

Core concept

A nodal region is a location where the chosen vibration field has little motion. Grain motion responds to the local field rather than to an arbitrary drawing. The particles have memory: changing a preset, frequency, exciter or plate does not directly teleport their positions.

Vibrating-plate model

The program uses a finite bank of modal shapes with resonant frequencies and frequency-dependent excitation weights. A virtual exciter at a chosen plate position favours modes that have appreciable displacement at that point. Moving the excitation point can therefore change the visible response even when the drive frequency stays constant.

The modal response depends on drive frequency, distance from resonant frequencies, quality factor Q, excitation point and relative tone amplitudes. Simultaneously excited tones contribute to a mean-square vibration measure: different excitation frequencies are treated incoherently, while same-frequency modal contributions can combine coherently.

How the sand moves

Each grain retains its own coordinates. At each simulation step, the script evaluates modal displacement and analytical spatial derivatives near the grains. A directional transport component encourages migration away from strongly vibrating regions, while stochastic motion, damping, mobility and excitation level control the visible agitation and settling.

This is a phenomenological grain-transport model, not a collision-resolved simulation of real sand. High noise produces broad moving clouds; stronger directed drift and damping can create sharper patterns. The Reset sand control redistributes grains, while ordinary mode and preset changes preserve their positions.

Ten resonance presets

Each preset specifies a concrete combination of model, modal indices, excitation amplitudes and movement parameters. Presets differ in the way they create spatial structure, not merely in colour or drawing style.

Explore and Sound-driven modes

With a valid selected Sound, the Source button or O cycles through Explore, resonance-based Sound and creative Sound. Without a suitable Sound, the lab remains usable in Explore mode. In Sound modes the analysed timeline drives changing spatial excitation; the control keys , and . change its traversal rate.

The script analyses the recording before the visual simulation. It does not provide live microphone input or synchronized Sound playback from within the Demo interface. Short or silent files may be rejected by the analysis safeguards.

On-screen controls

Some controls are context-sensitive: mode stepping and frequency changes act in Explore mode, while selected-Sound modes follow the analysed recording.

Keyboard shortcuts

Click the Demo window to give it keyboard focus before using the shortcuts.

Display and mouse interaction

Requirements and initial settings

Limitations & performance

• Model approximations: the free-square model is an illustrative modal approximation; the supported-plate model is exact only for its idealised boundary assumptions.
• Particle physics: grains follow a phenomenological drift/noise/damping rule, without full granular collisions or real-world calibration.
• Sound interpretation: resonance-based mapping estimates modal excitation from spectral bands; creative mapping is explicitly artistic. Neither reconstructs an actual plate experiment from arbitrary audio.
• Not live sound processing: Sound analysis is offline, and the lab does not play back the selected recording during visualisation.
• Rendering cost: higher grain counts, dense fields and overlays increase computation. Choose Fast when redraw becomes sluggish.
• Demo interaction: on newer Praat builds, running is divided into short takes followed by a safe input pause; use Start / Pause to continue.
• Display shape: the layout is optimised for a widescreen Demo window; other proportions can visually stretch the plate.

Musical and educational explorations

Learn how a node forms

Choose Fundamental Resonance, reset the sand and observe how an initially random cloud concentrates along quiet pathways. Toggle Nodal lines to compare the computed field with the visible accumulation.

Compose transitions rather than static forms

Start with Symmetric Cross and advance to Diagonal Interference without resetting. The original grains must travel toward the new equilibrium, making the transition itself the subject.

Observe competing resonances

Compare Dual-Mode Interference with Experimental Resonance to see how several tones can generate quiet regions that differ from any one isolated mode.

Explore timbre as spatial excitation

Select a voice, instrument or electronic texture and compare resonance-based Sound mapping with creative spectral mapping. The two interpretations can create very different spatial histories from the same recording.