Holophonics is a binaural recording system created by Hugo Zuccarelli, that is based on the claim that the human auditory system acts as an interferometer. It relies on phase variance, just like stereophonic sound. The sound characteristics of holophonics are most clearly heard through headphones; though they can be effectively demonstrated with two-channel stereo speakers, provided that they are phase-coherent. The word "holophonics" is related to "acoustic hologram".
Zuccarelli's company, Acoustic Integrity, also sells loudspeakers under the Holophonics brand.
Holophonics was created by Argentinian inventor, Hugo Zuccarelli, in 1980 during his studies at the Politecnico di Milano university. In 1983, Zuccarelli released a recording entitled Zuccarelli Holophonics (The Matchbox Shaker) in the United Kingdom (UK) that was produced by CBS. The recording consisted entirely of short recordings of sound effects designed to show off the Holophonics system. These included a shaking matchbox, haircut and blower, bees, balloon, plastic bag, birds, airplanes, fireworks, thunder and racing cars. In its early years, Holophonics was used by various artists, including Pink Floyd for The Final Cut (1983), Roger Waters on his solo album, The Pros and Cons of Hitch Hiking (1984) and Psychic TV's Dreams Less Sweet (1983). The system has been used in a film soundtrack, popular music, television and theme parks.
Zuccarelli states that the human auditory system is a sound emitter, producing a reference sound that combines with incoming sound to form an interference pattern inside the ear. The nature of this pattern is sensitive to the direction of the incoming sound. According to the hypothesis, the cochlea detects and analyzes this pattern as if it were an acoustic hologram. The brain then interprets this data and infers the direction of the sound. An article from Zuccarelli presenting this theory was printed in the magazine New Scientist in 1983. This article was soon followed by two letters, casting doubt on Zuccarelli's theory and his scientific abilities.
To date, there has been no evidence provided that any acoustic emissions are used for sound localization. Holophonics, like binaural recording, instead reproduces the interaural differences (arrival time and amplitude between the ears), as well as rudimentary head-related transfer functions (HRTF). These create the illusion that sounds produced in the membrane of a speaker emanate from specific directions.
There has been some controversy over the claims made by Hugo Zuccarelli regarding this recording technique. The effects achieved may be comparable to traditional binaural recording using mannequin heads, or via more traditional 3D audio techniques via HRTFs. There is no evidence, nor studies conducted, to indicate that the holophonic technique is substantially different from or superior to these methods, nor has Zuccarelli ever published his technique, nor has he allowed independent study of the results. The only available publication is a patent, which describes a fairly typical dummy-head binaural recording.
While otoacoustic emissions do exist, there is no evidence to support the assertion that these play a role in sound localization, nor is any mechanism for this "interference" effect claimed by Zuccarelli supported. On the contrary, there is abundant literature proving that properly presented spatial cues via HRTF synthesis (mimicking binaural heads) or binaural recording is adequate to reproduce realistic spatial recordings comparable to real listening, and comparable to the Holophonics demonstrations.
Recordings released using holophonics
- Pink Floyd, "The Final Cut" Harvest/E.M.I, 7243 8 31242 2 0 (1982).
- Roger Waters, "The Pros and Cons of Hitchhiking", Harvest, CDP 7 46029 2 (1984).
- Psychic TV, "Dreams Less Sweet", Some Bizarre (1983).
- Staff (1983–2012). "Hugo Zuccarelli". Acoustic Integrity. Acoustic Integrity, Inc. Retrieved 21 May 2012.
- Zuccarelli, Hugo; "Ears Hear by Making Sounds," New Scientist, 438-440 1983
- Baxter, A.J., and Kemp, David T.; "Zuccarelli's Theory," New Scientist, 606-606 1983
- "Process for forming an acoustic monitoring device", US Patent 4,680,856
- Gilkey & Anderson, "Binaural and Spatial Hearing in Real and Virtual Environments"
- Mabbett, Andy (2010). Pink Floyd - The Music and the Mystery. London: Omnibus,. ISBN 978-1-84938-370-7.