---
title: "Wavelength"
description: "Wavelength is the spatial distance over which one full cycle of a wave repeats. It is calculated as λ = c / f, where c is the speed of sound in the medium (~343 m/s in air at 20 °C) and f is the frequency in hertz. For industrial acoustic cleaning the wavelength is the single most informative dimension because it predicts how the horn's sound field will fill the vessel."
canonical_url: "https://sylio.co/glossary/wavelength"
last_updated: "2026-06-28T02:29:23.210Z"
---

**Wavelength** is the spatial distance over which one full cycle of a wave repeats. It is calculated as λ = c / f, where c is the speed of sound in the medium (~343 m/s in air at 20 °C) and f is the [frequency](/glossary/frequency) in hertz. For industrial acoustic cleaning the wavelength is the single most informative dimension because it predicts how the horn's sound field will fill the vessel.

## Wavelengths for industrial sonic horns

<table>
<thead>
  <tr>
    <th>
      Frequency
    </th>
    
    <th>
      Wavelength in air at 20 °C
    </th>
  </tr>
</thead>

<tbody>
  <tr>
    <td>
      12 Hz
    </td>
    
    <td>
      ~28 m
    </td>
  </tr>
  
  <tr>
    <td>
      30 Hz
    </td>
    
    <td>
      ~11 m
    </td>
  </tr>
  
  <tr>
    <td>
      60 Hz
    </td>
    
    <td>
      ~5.7 m
    </td>
  </tr>
  
  <tr>
    <td>
      75 Hz
    </td>
    
    <td>
      ~4.6 m
    </td>
  </tr>
  
  <tr>
    <td>
      125 Hz
    </td>
    
    <td>
      ~2.7 m
    </td>
  </tr>
  
  <tr>
    <td>
      230 Hz
    </td>
    
    <td>
      ~1.5 m
    </td>
  </tr>
  
  <tr>
    <td>
      400 Hz
    </td>
    
    <td>
      ~0.85 m
    </td>
  </tr>
</tbody>
</table>

Wavelengths in hot flue gas are longer than in cool air because the speed of sound rises with temperature — at 200 °C the speed of sound is about 436 m/s, stretching a 75 Hz wave to roughly 5.8 m.

## Why long wavelengths penetrate further

Acoustic energy diffracts efficiently around obstructions smaller than its wavelength. A 5-metre 60 Hz wave bends around tube rows, electrode spacings and baffles that would scatter or absorb a 1-metre 350 Hz wave. This is the underlying physics of why [low-frequency acoustic cleaners](/glossary/low-frequency-acoustic-cleaner) clean large open vessels better than [high-frequency](/glossary/high-frequency-acoustic-cleaner) units.

## Related terms

- [Frequency](/glossary/frequency)
- [Sound pressure level](/glossary/sound-pressure-level)
- [Standing wave](/glossary/standing-wave)
- [Low-frequency acoustic cleaner](/glossary/low-frequency-acoustic-cleaner)
- [High-frequency acoustic cleaner](/glossary/high-frequency-acoustic-cleaner)