Binaural recording

Binaural recording is a method of recording sound that uses two microphones, arranged with the intent to create a 3-D stereo sound sensation for the listener of actually being in the room with the performers or instruments. This effect is often created using a technique known as 'dummy head recording', wherein a mannequin head is outfitted with a microphone in each ear. Binaural recording is intended for replay using headphones and will not translate properly over stereo speakers. This idea of a three dimensional or 'internal' form of sound has also translated into useful advancement of technology in many things such as stethoscopes creating 'in-head' acoustics and IMAX movies being able to create a three dimensional acoustic experience. Binaural recording is a method of recording sound that uses two microphones, arranged with the intent to create a 3-D stereo sound sensation for the listener of actually being in the room with the performers or instruments. This effect is often created using a technique known as 'dummy head recording', wherein a mannequin head is outfitted with a microphone in each ear. Binaural recording is intended for replay using headphones and will not translate properly over stereo speakers. This idea of a three dimensional or 'internal' form of sound has also translated into useful advancement of technology in many things such as stethoscopes creating 'in-head' acoustics and IMAX movies being able to create a three dimensional acoustic experience. The term 'binaural' has frequently been confused as a synonym for the word 'stereo', and this is partially due to a large amount of misuse in the mid-1950s by the recording industry, as a marketing buzzword. Conventional stereo recordings do not factor in natural ear spacing or 'head shadow' of the head and ears, since these things happen naturally as a person listens, generating their own ITDs (interaural time differences) and ILDs (interaural level differences). Because loudspeaker-crosstalk of conventional stereo interferes with binaural reproduction, either headphones are required, or crosstalk cancellation of signals intended for loudspeakers such as Ambiophonics is required. For listening using conventional speaker-stereo, or mp3 players, a pinna-less dummy head may be preferable for quasi-binaural recording, such as the sphere microphone or Ambiophone. As a general rule, for true binaural results, an audio recording and reproduction system chain, from microphone to the listener's brain, should contain one and only one set of pinnae (preferably the listener's own) and one head-shadow. With a simple recording method, two microphones are placed 18 cm (7') apart facing away from each other. This method will not create a real binaural recording. The distance and placement roughly approximates the position of an average human's ear canals, but that is not all that is needed. More elaborate techniques exist in pre-packaged forms. A typical binaural recording unit has two high-fidelity microphones mounted in a dummy head, inset in ear-shaped molds to fully capture all of the audio frequency adjustments (known as head-related transfer functions (HRTFs) in the psychoacoustic research community) that happen naturally as sound wraps around the human head and is 'shaped' by the form of the outer and inner ear. The Neumann KU-81, and KU-100 are the most commonly used binaural packages, especially by musicians. A simplified version of binaural recordings can be achieved using microphones with a separating element, like the Jecklin Disk. Not all cues required for exact localization of the sound sources can be preserved this way, but it also works well for loudspeaker reproduction. In the late 1960s, Aiwa and Sony offered headphones with a pair of microphones mounted on the headband around two inches above the ears. These allowed pseudo-binaural recordings to be made. Miniature binaural 'in-ear' or 'near-ear' microphones can be linked to a portable Digital Audio Tape (DAT) or MiniDisc recorder, bypassing the need for a dummy head by using the recordist's own head. The first clip-in binaural microphones using the recordist's own head were offered by Sennheiser in 1974. The first clip-on binaural microphones using the recordist's own head were offered by Core Sound LLC in 1989. The first completely 'in-ear' binaural microphones using the recordist's own head were offered by Sound Professionals in 1999. Roland Corporation also offers its CS-10EM in-ear binaural microphone set. The technique of binaural re-recording is simple, but has not been well established. It follows the same principles of Worldizing, a technique used by film sound designers in which sound is played over loud speaker in a real world location and then re-recorded, taking along all the aspects and characteristics of the real world environment with it. Using space to manipulate a sound and then being re-recorded is also nothing new as it is something that has been done through the use of echo-chambers in recording studios for many years. In 1959, an echo-chamber was famously used by Irving Townsend during the post production process of Miles Davis's 1959 album 'Kind of Blue'. ' just a bit of sweetening. At 30th Street, a line was run from the mixing console down into a low-ceilinged, concrete basement room - about twelve by fifteen feet in size - where we set up a speaker and a good omnidirectional microphone.' In binaural re-recording, a binaural microphone is used to record content being played over a multi-channel speaker set-up. The binaural head, or microphone, is therefore theoretically making a recording of how humans will hear multi-channel content. The soundtrack to a film for example will be recorded by the binaural microphone with all the environmental cues of the given location, as well as reverberations, including those commonly created by our own torso (assuming a HATS model is used). This method, like certain binaural recordings made with a Neumann KU100 or HATS model for example, can produce convincing 3D sound.