Spatial sound is the scientific name for surround sound, the natural process by which humans hear. Spatial sound or surround sound can be achieved through the use of multiple speakers ranging in number from two to twenty-four. Using three surround or back channels in association with three front or 2D channels home audio surround sound is possible through the use of a tuner or amplifier for daily use. Spatial sound is based on timing; human hearing uses this property of sound to locate aurally any sound they hear. Delays in the reflection and reverberation allow for the direction and distance to the sound to be heard. Developing this concept into spatial sound at home is achieved through audio engineering and mixing principles used by the master engineer and audio technician during the production phase of a video, movie or television program.
Three dimensional sound is an extension of spatial and surround sound and is used in everything from DVD production to audio CDs at this time in its technological history. Three dimensional recordings use a virtual environment controlled by computer parameters that mimic natural hearing in particular environments such as a forest or a train station. Think of this as a simulated surround sound system where the viewer or listener feels as if they are in the middle of the sound or audio. Effects noticed by people using or listening to three dimensional sound recordings report a better personal connection to the event or image they are watching like feeling as if they are in the band.
Binaural set ups pick up the audio in the same fashion as the human ears creating the best possible recording technique for headphone listening. The "dummy" head helps to alleviate additional engineering and mixing to achieve the natural hearing effect, as it is built form materials with the same auditory properties as the human head. This include sound absorption, deflection, reflection, and diffraction. This principles of head shadowing and natural ear spacing in binaural recording is not employed in standard stereo recordings and the effect is not possible in stereo. Similar effects can be attained through the use of advanced engineering and digital effects processors but at an increased cost.
Ambisonics is an audio technology term that deals with the velocity and pressure of a sound wave or waves to represent a sound field in its natural state. In other words it is the recorded ambient sound of an environment. The recorded ambient sound is then reproduced over a loud speaker system for auditory effects. In reality, upwards of forty thousand speakers would be needed to reproduce the environment accurately so engineers and audio specialists use a scaled down version and represent the sound in a representational format using limited speakers and channels. Ambisonics was the beginning of, and an alternative, to surround sound and its roots can be traced back to the nineteenth century. Binaural recording is an adaptation of these principles. The secret in ambisonics is the placement of approximately nine microphones in varying angles and positions to capture the most of an environment's sound image.
