Horn Directivity

Author: N.H. Crowhurst

Like the original megaphone, horns tend to be directional in their radiation of sound. The strongest part of the wave is the section formed by the horn development. Radiation outside this angle is due to a kind of spill-over.

Directivity of a megaphone

The directivity of a horn is dependent on its precise shaping. For example, a shape called the tractrix, which is nearly identical with the exponential shape, except at the mouth, is designed to produce hemispherical waves; in other words, to cover the entire 180° in front of its mouth. This ideal distribution from the tractrix only exists at the lower frequencies it radiates. At higher frequencies, the bell has progressively less effect.

Difference in bell shape affects radiation