Core technology
Bell horn
Also known as bell-shaped horn, exponential bell horn, exponential horn.
A bell horn is the conical or exponential flare bolted to the driver of an industrial sonic horn. Its job is to transform the high-impedance, small-area pressure pulse from the diaphragm or piston-whistle into a lower-impedance, larger-area sound wave that couples efficiently into the gas inside the vessel.
Why the geometry matters
The bell is not decorative. Its flare profile — usually exponential, sometimes catenoidal or tractrix — sets the horn's cut-off frequency: below the cut-off, the bell stops behaving as a horn and the radiated sound power collapses. A 60 Hz low-frequency acoustic cleaner therefore needs a physically larger bell than a 230 Hz unit, which is why low-frequency horns are noticeably bulkier and heavier. Mounting orientation, flange standard (DN or ANSI 150) and the bell's projection distance into the vessel are all selected to match the cleaning target geometry.
Materials
- Carbon steel for ambient-temperature mounting on cool-side ducts, silos and hoppers
- 316 stainless steel for corrosive or food-grade environments
- Inconel 625 or 718 for hot-side service above 350 °C, including SCR reactors, air heater penthouses and recovery-boiler flue paths
Related terms
Related terms
- 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.
- Diaphragm hornA diaphragm horn is a sonic horn whose sound is generated by a vibrating titanium or stainless-steel diaphragm driven by pulsed compressed air. The dominant form-factor for low-frequency industrial cleaning.
- Piston-whistle hornA piston-whistle horn generates sound through a moving piston or rotating disc rather than a vibrating diaphragm. Best suited to high-frequency cleaning duty on fabric filters and catalyst layers.
- Acoustic hornAn acoustic horn is the broader term for any low-frequency horn-shaped sound emitter used in industrial cleaning. In commercial practice it is interchangeable with sonic horn.