Acoustic Horns Information
Acoustic horns produce vibrations at relatively low frequencies in order to remove soot and other buildups of particulates from chimneys, catalyst beds, or other process vessels. They can reach areas that are inaccessible to slag and ash removal devices such as long soot blowers, wall blowers, and water cannons. Acoustic horns are relatively inexpensive to operate, but must be used frequently in order to prevent the buildup of undesirable particles. Most products achieve sound pressures of approximately 150 dB and work over two ranges of operating frequency. Acoustic horns that work in the infrasonic or near-infrasonic frequency range are used mainly with boilers and selective catalytic reduction (SCR) reactors. Acoustic horns that operate above 75 Hz are designed to avoid resonance with other plant equipment. Acoustic horn suppliers are located across North America and around the world. Some companies refer to their products as sonic horns or acoustic cleaners.
Product specifications for acoustic horns include fundamental frequency, output power level, materials of construction, weight, length, air consumption, and shape. Fundamental frequency, the predominant frequency in a complex waveform, provides the sound with its strongest referential pitch. Weight and length are measured in English units such as pounds (lbs) and inches (in), or metric units such as kilograms (kg) and millimeters (mm). Sonic horns with lower fundamental frequencies are larger in size and provide a larger cleaning area. Smaller acoustic cleaners provide higher fundamental frequencies and a smaller cleaning area. Aluminum, titanium, steel, and stainless steel are common materials of construction for acoustic horns. The fared portion can be square, rectangular or conical in shape. Typically, the acoustic horn is optimized for multiple single frequencies as well as a band of frequencies.
Acoustic horns use compression drivers, transducers that provide relatively high pressure and low displacement. They are designed to provide smoothness of frequency response, smoothness of power response, tonal balance, low distortion, high efficiency and time alignment. Throat area, mouth area, horn length, compression chambers, and expansion contour are important factors to consider.