Spatial Audio Processing: MPEG Surround and Other Applications

1.1 The human auditory system

The human auditory system serves several important purposes in daily life. One of the most prominent features is to understand spoken words, which allows people to communicate in an efficient and interactive manner. In case of potential danger, the auditory system may provide means to detect dangerous events, such as an approaching car, at an early stage and react accordingly. In such cases, the great advantage of the auditory system compared with the visual system is that it allows us to monitor all directions simultaneously, including positions behind, above and below. In fact, besides a 360-degree ‘view’ in terms of both elevation and azimuth, the auditory system also provides an estimate of the distance of sound sources. This capability is remarkable, given the fact that humans have only two ears and yet are capable of analyzing an auditory scene in multiple dimensions: elevation, azimuth, and distance, while recognition of a sound source might be considered as a fourth dimension.

But besides being a necessary means for communication and to provide warning signals, the human hearing system also provides a lot of excitement and fun. Listening to music is a very common activity for relaxation and entertainment. Movies rely on a dedicated sound track to be exciting and thrilling. Computer games become more lifelike with the inclusion of dedicated sound tracks and effects.

In order to enjoy music or other audio material, a sound scene has to be recorded, ...