Emitter line

In acoustics, a radiator line is an equidistant arrangement of N point-shaped individual sound sources ( monopoles ). Due to the superposition of individual waves , the origin of which lies in the individual sources, a directional characteristic is created . In practice, this is used for targeted sound reinforcement or, in the case of microphones, for directed recording. Examples are the sound reinforcement of churches or train stations.

With the same sound flow for all monopoles, three cases can be distinguished for the directional characteristic of the radiator row:

1. The entire length of the radiator line is smaller than the wavelength of the emitted sound. This results in an undirected radiation (see breathing sphere ).
2. The distance d between two individual sources is smaller than the wavelength . There is a maximum. ${\displaystyle \lambda }$
3. The sources are more distant than one wavelength from one another, which leads to several maxima.

Mathematically, the directional characteristic can be determined as follows:

${\displaystyle R(\alpha )={\frac {1}{N}}\cdot {\frac {\sin(\pi {\frac {d}{\lambda }}N\cos(\alpha ))}{\sin(\pi {\frac {d}{\lambda }}\cos(\alpha ))}}}$

Furthermore, the directional characteristic can be pivoted relative to one another by delays in the individual sound sources. By decreasing the sound flux towards the outside, side lobes can be suppressed with a lower directivity of the main lobe .

literature

• Heinrich Kuttruff: Acoustics, an introduction. Hirzel Verlag, Stuttgart, 2004, ISBN 3-7776-1244-8