Glossary
Acoustics and physics
Frequency
Also known as Hz, acoustic frequency, sonic horn frequency.
Frequency is the number of acoustic cycles per second, measured in hertz (Hz). For industrial acoustic cleaning it is the single most important selection parameter after SPL: frequency determines wavelength, which in turn governs how the sound wave penetrates the vessel.
Industrial cleaning bands
| Band | Range | Wavelength in air | Typical use |
|---|---|---|---|
| Infrasonic | 12–30 Hz | 11–28 m | Recovery boilers, WtE flue paths |
| Low frequency | 60–250 Hz | 1.4–5.7 m | ESPs, preheater cyclones, silos |
| High frequency | 250–450 Hz | 0.75–1.4 m | Fabric filters, SCR catalysts |
Trade-off
Long wavelengths diffract around obstructions and penetrate further; short wavelengths concentrate more energy in a smaller volume. The frequency choice is therefore a trade between reach and energy density. Many real installations combine both bands: low-frequency horns clean the bulk volume; high-frequency horns clean dense bag rows or catalyst faces.
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.
- Sound pressure levelSPL is the logarithmic measure of sound pressure in decibels relative to a 20 µPa reference. Industrial sonic horns operate at 140–180 dB SPL.
- 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.
- Low-frequency acoustic cleanerLow-frequency acoustic cleaners operate at 60–250 Hz. The long wavelength penetrates deep into large open vessels such as ESPs, recovery boilers and cement preheater cyclones.
- High-frequency acoustic cleanerHigh-frequency acoustic cleaners operate at 250–450 Hz. The shorter wavelength carries more energy per unit volume and suits fabric filters, SCR catalysts and small hopper geometries.
- Infrasonic cleanerAn infrasonic cleaner operates below the audible threshold (typically 12–30 Hz). The very long wavelength penetrates further than a conventional sonic horn and is preferred on recovery boilers and WtE flue paths.