Pure sine tones. The plate only answers strongly near its own resonances, so some tones form clean patterns and others form weak mixes.

Plate: 30 × 30 cm steel, 1 mm, driven at the centre. Mode n×m rings at 26.65 × (n² + m²) Hz. Only even n, m move at the centre, so patterns run from 107 Hz (0×2) to 6.8 kHz. Sound between modes gives a weak or mixed pattern.