Binaural recording

Binaural recording is a method of recording sound that uses two microphones, arranged with the intent to create a 3D 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 fitted 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", due in part to systematic use 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 interaural time differences (ITDs) and interaural level differences (ILDs) specific to their listening position.

The history of binaural recording goes back to 1881. The first binaural unit, the théâtrophone, was invented by Clément Ader. It consisted of an array of spaced pairs of carbon pencil microphones installed along the front edge of the Opera Garnier. The signal was sent to subscribers through the telephone system, and required that they hold a headset up to each ear.

In the early 1930's, several binaural heads were developed. One, referred to as "Oscar" was made by Bell Labs, using 1.4 in (36 mm) microphones inserted into the cheeks of a mannequin's head, and was demonstrated at the World Fair in Chicago, in 1933. The Dutch firm, Philips, also developed a binaural head, with the microphones located at the ears, which produced a better result. These early adaptations of the mannequins used in shops to model clothes led to the moniker "dummy head".

Over the course of the 20th century, advancements in microphone design and an understanding of the significance that the anatomy of the human ear played in the localization of sound led to further developments in the design of binaural heads. Their use ranged from acoustic analysis, such as to record word scoring for speech intelligibility measurement, hearing aid design, for music reproduction, and radio drama.

Demolition (1973) was the first radio drama recorded using a dummy head.

In 1974, Virgin Records issued the first solo album by Tangerine Dream's leader Edgar Froese, titled Aqua. The sleeve notes inform listeners that the tracks NGC 891 and Upland were recorded using a binaural head system developed by Gunther Brunschen. Listeners were advised to listen with stereo headphones. Although Edgar was keen to continue to use this system for subsequent recordings, it was abandoned because although it worked well through headphones, the improved sound quality did not translate adequately to a hi-fi speaker system.

In 1972, Neumann released the KU80 binaural head, which would eventually lead to the KU100 binaural head, which is widely used today.^{[citation needed]}