The term omnidirectional is used in radio engineering and acoustics. In radio engineering, it refers to the radiation and reception of radio waves from antennas, and in acoustics, it refers to the directionally insensitive sound radiation from loudspeakers, as well as sound reception from microphones.
As far as antenna technology is concerned, omnidirectional antennas have a radiation characteristic in which the electromagnetic waves are radiated spherically in all directions. Antennas with such a radiation characteristic are omnidirectional or omnidirectional radiators. Their radiation in the horizontal plane is 360 degrees. It does not matter whether the antenna is a transmitting antenna or a receiving antenna. As a receiving antenna, an omnidirectional antenna receives the radio signals from all directions.
Radio waves and sound waves
There are directional differences between radio technology and sound technology with regard to the radiation and reception of radio waves and sound waves. For radio waves, the radiation characteristics of the antennas are important, while sound waves are concerned with the directional characteristics of loudspeakers and microphones. If the radiation occurs in only one direction, it is called unidirectional radiation. A bidirectional radiation is given, if the radiation takes place in two directions. Omnidirectional radiation of a loudspeaker is when the radiation occurs evenly in all directions and none is preferred.
Such omnidirectional radiating loudspeakers are radial radiators or spherical loudspeakers. However, the direction and characteristics of the radiation depend on the sound frequency. Woofer radiate tones from under 150 Hz approximately spherical. The situation is different with tweeters and midrange drivers, which radiate sound unidirectionally.
Microphones with omnidirectional polar patterns receive sound spherically from all directions with equal sensitivity. Corresponding microphones are used for orchestra and choir recordings and also in home studios.