Acoustics and physics
Standing wave
Also known as stationary wave, acoustic standing wave.
A standing wave is the stationary interference pattern produced when an outgoing sound wave overlaps with its reflection from a vessel boundary. Pressure does not propagate; instead it oscillates in fixed positions of high amplitude (antinodes) separated by positions of zero amplitude (nodes) spaced one half-wavelength apart.
Implications for cleaning
Cleaning energy is delivered at antinodes; nodes do almost nothing. In a vessel small enough for standing waves to form, a single horn can leave predictable dead zones where deposits continue to build. Multi-horn array design, off-axis mounting and dithering the firing sequence are the practical countermeasures.
When standing waves dominate
Standing-wave behaviour is strongest in vessels whose internal dimensions are comparable to the wavelength. A 60 Hz horn (λ ≈ 5.7 m) interacts strongly with vessels of similar size; in much larger vessels the wave is too small to form clean standing patterns and the energy distribution is closer to a free-field projection.
Related terms
Related terms
- WavelengthWavelength is the distance a sound wave travels in one cycle. At 60 Hz in air a wave is 5.7 m long; at 400 Hz it is 0.85 m. Wavelength governs how far a sonic horn's cleaning reach extends.
- ResonanceResonance is the amplification that occurs when a driving frequency matches a natural mode of a system. It is exploited by sonic horns and avoided in tube-bank installation design.
- FrequencyFrequency is the number of acoustic cycles per second, measured in hertz. Industrial acoustic cleaners operate at 12–30 Hz (infrasonic), 60–250 Hz (low) or 250–450 Hz (high).