---
title: "Frequency (Hz)"
description: "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."
canonical_url: "https://sylio.co/glossary/frequency"
last_updated: "2026-06-28T02:29:22.877Z"
---

**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](/glossary/sound-pressure-level): frequency determines [wavelength](/glossary/wavelength), which in turn governs how the sound wave penetrates the vessel.

## Industrial cleaning bands

<table>
<thead>
  <tr>
    <th>
      Band
    </th>
    
    <th>
      Range
    </th>
    
    <th>
      Wavelength in air
    </th>
    
    <th>
      Typical use
    </th>
  </tr>
</thead>

<tbody>
  <tr>
    <td>
      Infrasonic
    </td>
    
    <td>
      12–30 Hz
    </td>
    
    <td>
      11–28 m
    </td>
    
    <td>
      <a href="/glossary/recovery-boiler">
        Recovery boilers
      </a>
      
      , <a href="/glossary/waste-to-energy">
        WtE
      </a>
      
       flue paths
    </td>
  </tr>
  
  <tr>
    <td>
      Low frequency
    </td>
    
    <td>
      60–250 Hz
    </td>
    
    <td>
      1.4–5.7 m
    </td>
    
    <td>
      <a href="/glossary/electrostatic-precipitator">
        ESPs
      </a>
      
      , <a href="/glossary/preheater-cyclone">
        preheater cyclones
      </a>
      
      , <a href="/glossary/silo">
        silos
      </a>
    </td>
  </tr>
  
  <tr>
    <td>
      High frequency
    </td>
    
    <td>
      250–450 Hz
    </td>
    
    <td>
      0.75–1.4 m
    </td>
    
    <td>
      <a href="/glossary/fabric-filter">
        Fabric filters
      </a>
      
      , <a href="/glossary/selective-catalytic-reduction">
        SCR catalysts
      </a>
    </td>
  </tr>
</tbody>
</table>

## 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

- [Wavelength](/glossary/wavelength)
- [Sound pressure level](/glossary/sound-pressure-level)
- [Fundamental frequency](/glossary/fundamental-frequency)
- [Low-frequency acoustic cleaner](/glossary/low-frequency-acoustic-cleaner)
- [High-frequency acoustic cleaner](/glossary/high-frequency-acoustic-cleaner)
- [Infrasonic cleaner](/glossary/infrasonic-cleaner)