Directional Sound refers to the notion of using various devices to create fields of sound which spread less than most traditional loudspeakers. Several techniques are available to accomplish this, and each has their benefits and drawbacks.

Systems which guide evacuees during an emergency by the emission of pink noise to the exits are often also called "directional sound" sytems. Pink noise spectrum Pink noise ( ), also known as 1/f noise or flicker noise, is a signal or process with a frequency spectrum such that the power spectral density is proportional to the reciprocal of the frequency. ...

Basic Theory

In all wave producing sources, the directivity of any beam, at maximum, corresponds to the size of the source compared to the wavelengths it is generating. The larger the source is compared to the wavelength of the sound waves, the more directional beam results.

Sound waves have dimensions of inches to many feet, which is approximately the size of most loudspeaker systems. At high frequencies, however, the wavelengths are quite short, which can result in a narrow distribution of sound from the tweeters in a conventional loudspeaker system.

Large Speaker Arrays

One method of creating directivity utilizes very large arrays of loudspeakers, all driven together in-phase. This creates a very large source size compared to wavelength, and the resulting sound field is narrowed. This is often used in arena sound systems, to mitigate noise that would ordinarily travel to adjoining neighborhoods. A loudspeaker is a device which converts an electrical signal into sound. ...

While the technique does work for stadium-size systems, because of the large physical dimensions of the speaker arrays, and the resulting sound field, it is not practical for smaller installations.

See also

• Loudspeaker