Acoustics and physics
Resonance
Also known as resonant frequency, acoustic resonance.
Resonance is the amplification of vibration that occurs when a driving frequency matches a natural mode of a system. It is the mechanism by which a diaphragm horn sustains 140–180 dB output from modest pneumatic input — the diaphragm and bell are tuned so the driving pressure pulse hits their natural frequency.
Two faces in industrial cleaning
Useful resonance. The horn itself; matching certain horn fundamentals to the bulk dimensions of a cleaning target so the sound field fills the vessel uniformly.
Hazardous resonance. Tube banks, fan blades, duct walls and damper assemblies all have their own natural frequencies. If a sonic horn's fundamental or one of its harmonics coincides with a structural mode, sustained vibration can fatigue welds or loosen fixings. Multi-horn installation design routinely includes a vibration check against the equipment's modal map.
Related terms
Related terms
- Fundamental frequencyThe fundamental frequency is the lowest natural resonant frequency of a system. For a sonic horn it is the published nameplate frequency at which the horn delivers maximum cleaning energy.
- HarmonicA harmonic is an integer multiple of the fundamental frequency. A sonic horn radiates energy mainly at its fundamental, with progressively less at higher harmonics.
- Standing waveA standing wave is a stationary interference pattern that creates nodes (zero pressure, low cleaning) and antinodes (peak pressure, high cleaning). Horn placement is designed to minimise dead zones.
- Sonic hornA sonic horn is a pneumatically-driven low-frequency sound emitter (typically 60–400 Hz at 140–180 dB SPL) used to dislodge particulate fouling from boilers, ESPs, baghouses and process vessels.