# A Review of Sound Field Control
## 1 Introduction  
Sound field control (SFC) technology aims to generate the desired sound field over a target area through secondary sound sources or actuators. It has a wide range of applications and generally includes sound field reproduction, personal audio systems, and active noise control.  
Sound field reproduction technology reconstructs the original sound field using secondary sound sources, so that the listener can obtain an immersive listening experience. Sound field reproduction can be divided into binaural sound field reproduction and large region sound field reproduction according to the size of the control area. Binaural sound field reproduction uses headphones or loudspeakers to reproduce the desired sound field in both ears [1, 2, 3] which can find applications in augmented reality (AR) and virtual reality (VR) products. It is essentially a virtual sound field reproduction method based on the perception characteristics of human ears. Large region sound field reproduction creates the desired sound field in an extended region [5, 6, 7, 8, 9]. This reproduction method has a larger listening area compared with the binaural one but requires a larger number of loudspeakers. Therefore, its practical application in entertainment is limited, and this method is more suitable for laboratory use and demonstration.  
The control area of the sound field reproduction technology is a single listening area, and the personal audio systems require that the original sound field is reproduced in the listening area while unwanted interferences are reduced in other areas [10, 11, 12]. Therefore, the control area for personal audio systems is divided into two kinds of zones: the acoustic bright zone, a listening area where the desired sound field is reproduced; and the acoustic dark zone, a quiet area where the sound pressure level needs to be suppressed. Personal audio systems can be used on TVs and tablet computers to produce directional sound to avoid interference with people around and are used in museums and other occasions to avoid the influence of sound from other sources (e.g., when the audio guides of multiple exhibits operate simultaneously).  
Different from sound field reproduction and personal audio systems which reproduce the desired sound field in a certain area, active noise control technology can suppress the original sound field in the target area to create a quiet environment for the listeners through generating a secondary sound field with the same amplitude as and the opposite phase to the original noise field according to the interference principle of sound waves [13; 14; 15]. Compared with passive control technologies, the active ones are more suitable for low frequency noise. Active noise control can be divided into binaural active noise control, local area active noise control, and global active noise control from the size of the control area. A typical application of binaural active noise control is the active noise control headphones, where the control area is at the eardrum. Local area active noise control generally refers to the reduction in noise in the user's head area, such as an active noise control headrest. Global active noise control is to achieve noise reduction in an entire space, such as the active control of cabin interior noise and aircraft radiated sound.  
This article introduces some of the research progress in sound field reproduction technology, personal audio systems, and active noise control technology in recent years.