---
title: "Sonic horn"
description: "A sonic horn is a pneumatically-driven sound emitter that produces high-intensity, low-frequency sound waves — typically between 60 and 400 Hz at sound pressure levels of 140 to 180 dB — used to dislodge particulate fouling from inside industrial process equipment. Sonic horns are the most common form of acoustic cleaner and the default specification for cleaning ESPs, baghouses, SCR catalysts, boiler heat-transfer surfaces and hoppers and silos."
canonical_url: "https://sylio.co/glossary/sonic-horn"
last_updated: "2026-06-28T02:29:29.890Z"
---

A **sonic horn** is a pneumatically-driven sound emitter that produces high-intensity, low-frequency sound waves — typically between 60 and 400 Hz at sound pressure levels of 140 to 180 dB — used to dislodge particulate fouling from inside industrial process equipment. Sonic horns are the most common form of [acoustic cleaner](/glossary/acoustic-cleaner) and the default specification for cleaning [ESPs](/glossary/electrostatic-precipitator), [baghouses](/glossary/fabric-filter), [SCR catalysts](/glossary/selective-catalytic-reduction), [boiler heat-transfer surfaces](/glossary/superheater) and [hoppers and silos](/glossary/hopper).

## How a sonic horn works

Compressed plant air admitted through a [solenoid valve](/glossary/solenoid-valve) drives a metal diaphragm — typically titanium or 316 stainless — into resonant oscillation at the horn's fundamental frequency. The oscillating pressure field is amplified by an exponential bell horn and projected into the vessel as a near-spherical sound wave. Particulate already deposited on internal surfaces receives an oscillating acceleration that overcomes adhesion; loosened material is then carried out with the gas flow before it can sinter, bridge or bond. Because the cleaning is acoustic and non-contact, the horn can fire while the plant is online without tube erosion, refractory damage or thermal shock.

## Key parameters

<table>
<thead>
  <tr>
    <th>
      Parameter
    </th>
    
    <th>
      Typical range
    </th>
  </tr>
</thead>

<tbody>
  <tr>
    <td>
      Fundamental frequency
    </td>
    
    <td>
      60–400 Hz
    </td>
  </tr>
  
  <tr>
    <td>
      Sound pressure level
    </td>
    
    <td>
      140–180 dB
    </td>
  </tr>
  
  <tr>
    <td>
      Compressed-air consumption
    </td>
    
    <td>
      8–14 Nm³/min at 4–7 bar
    </td>
  </tr>
  
  <tr>
    <td>
      Operating temperature (with appropriate materials)
    </td>
    
    <td>
      −40 °C to +500 °C
    </td>
  </tr>
  
  <tr>
    <td>
      Firing cycle
    </td>
    
    <td>
      5–15 s burst, repeated every 3–15 minutes
    </td>
  </tr>
  
  <tr>
    <td>
      Mass
    </td>
    
    <td>
      15–60 kg depending on horn size
    </td>
  </tr>
</tbody>
</table>

## Frequency selection

Lower frequencies (60–125 Hz) project longer wavelengths and penetrate further into large open vessels — [preheater cyclones](/glossary/preheater-cyclone), [recovery-boiler superheaters](/glossary/recovery-boiler), large [ESP fields](/glossary/esp-field-bus-section), [silos](/glossary/silo). Higher frequencies (230–400 Hz) carry more energy per unit volume and suit finer dust loads in [fabric-filter compartments](/glossary/fabric-filter), [catalyst layers](/glossary/honeycomb-catalyst) and smaller hopper geometries. See [low-frequency acoustic cleaner](/glossary/low-frequency-acoustic-cleaner) and [high-frequency acoustic cleaner](/glossary/high-frequency-acoustic-cleaner).

## Sonic horn vs steam sootblower

Sonic horns are increasingly specified alongside or in place of [steam sootblowers](/glossary/steam-sootblower) because they consume no boiler-grade steam, cause no tube erosion, require almost no moving parts and can fire every few minutes without operator intervention. They are less effective on hard, fused slag than retractable steam lances, so on furnace waterwalls and high-temperature superheaters they typically complement rather than replace mechanical cleaning.

## Related terms

- [Acoustic cleaner](/glossary/acoustic-cleaner)
- [Sonic sootblower](/glossary/sonic-sootblower)
- [Bell horn](/glossary/bell-horn)
- [Diaphragm horn](/glossary/diaphragm-horn)
- [Low-frequency acoustic cleaner](/glossary/low-frequency-acoustic-cleaner)