Welcome to Cochlear Concepts, LLC.
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Eric L. Carmichel, owner, can be reached at

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1534 N Dorsey Ln
Tempe, AZ 85281





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ELC Audio Engineering (click on image)

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The rotating head figure (above) was unashamedly borrowed from Jérôme Daniel's Ambisonics and 3D Research website. His website, doctoral thesis, and highly informative PowerPoint presentation (in French) on high-order Ambisonics can be accessed here: gyronymo.free.fr/index.html

We will be adding a comprehensive bibliography on Ambisonics, to include direct web links to articles when possible. A number of sites are quite good, but I avoid providing direct links to sites that have pop-up ads (the ads may be benign, but I don't want to alienate anyone because of dubious ads). For readers who are new to Ambisonics, a good place to start is ambisonic.net (noting that it's ambisonic, not ambisonics). Another highly recommended source of information on Ambisonics is the Audio Engineering Society (aes.org); in particular, the AES anthologies on Spatial Sound Techniques (Parts I and II). I am currently reviewing a number of web sites regarding Ambisonics in addition to reading a long list of journal articles on 3D recording and playback techniques.

Ambisonics is an appropriate technology for researching the effects of noise using normal- and hearing-impaired listeners. Controlled, real-world listening tests will enhance the external validity of research and claims regarding hearing aids, cochlear implants and EAS, as well as assistive communication devices. Many knowledgeable authors have attempted to explain Ambisonics terms. Their explanations generally make it clear that the Ambisonic W, X, Y, and Z signals are NOT speaker feeds (i.e., they're not the same as the signals ultimately routed to the loudspeakers). What most authors fail to explain, however, is that the W, X, Y, and Z signals aren't the signals originating from the microphone capsules either. If one attempts to make Ambisonics recordings using separate microphones, the unprocessed microphone signals, as with the speaker feeds, are not the same as the often-referenced Ambisonic W, X, Y, and Z signals.

Ambisonic B-format signals are not speaker feeds. Neither are these power lines (egad!).


Brief note regarding Ambisonic microphone techniques: Michael Gerzon, Peter Craven et al expanded upon the stereo concepts pioneered by Alan Blumlein to develop the concept of a microphone system that could reproduce a full three-dimensional soundfield. Both Blumlein and Gerzon realized that only when a sound wave is captured at a single point in space can it be reproduced faithfully and without the phase distortion anomalies inherent in spaced microphone techniques. Microphones designed for first-order Ambisonic recordings use four carefully-matched sub-cardiod microphone elements situated on a tetrahedral mount. The Soundfield DSF-1 is one such microphone, as is the Core Sound TetraMic. Higher-order recordings can be made using mh acoustics' 32-element em32 Eigenmike® microphone array.

Keith Howard's audiosignal.co.uk website is a nice resource for Michael Gerzon's early writings on audio-related topics. This resource includes articles that appeared in Hi-Fi News, Studio Sound, and Wireless World (please note that a lot of these articles are not related to Ambisonics). Keith Howard's "Gerzon archive" can be accessed directly here: Gerzon archive.


An Ambisonic microphone: Core Sound's TetraMic