near field
- In high- frequency technology, the electromagnetic field in the vicinity of the antenna, which behaves differently from the far field due to interference, is referred to as the near field. The near field lies in a distance range from the antenna that corresponds to the wavelength of the high-frequency source. This field also depends on the antenna and its radiation characteristics. For example, in the case of strongly bundled radiation, the near field is shortened to about one fifth of the wavelength. At 1 MHz, the near field is about 300 m, at 100 MHz between 1 m and 3 m. Near fields are decisive for capacitive and inductive interference.
- Inacoustics, the near field is the area near the sound source in which the sound wave builds up. In the near field, sound wave propagation occurs with spherical waves. In the near field, the distance to the sound source is less than or equal to the wavelength. In this range, which can extend up to ten times the wavelength, the sound pressure and the sound velocity are not proportional to each other.