ORTF Stereo Microphone Technique
From WikiRecording
What is ORTF
ORTF stands for Office de Radiodiffusion-Télévision Française. It was first adopted by french radio.
The result is a realistic stereo field that has reasonable compatibility with mono playback (little phase cancelation. Since the cardioid polar pattern rejects off-axis sound, less of the ambient room characteristics are picked up. This means that the mics can be set back further from the sound sources, resulting in a blend that may be more appealing. Further, ORTF is easy to achieve, as purpose-built microphone mounts are available.
Setup
ORTF combines both the volume difference provided as sound arrives on- and off-axis at two cardioid microphones spread to a 110º angle, as well as the timing difference provided as sound arrives at two the microphones spaced approximately 17 cm apart.
As with all microphone arrangements the distance and angle can be manually adjusted slightly by ear for the best sound, which may vary depending on room acoustics, source characteristics, and so on. But this arrangement is defined as it is because it was the result of considerable research and experimentation, and its results are predictable and repeatable.
These interchannel differences have nothing to do with interaural differences, which come only from artificial head recordings. Even the spacing of 17 cm has nothing to do with interaural ear spacing. The recording angle for this microphone system is ±48° = 96° (http://www.sengpielaudio.com/RichtungslokalisationBeiStereo2.pdf).
Sources
Parts of this article are copied from this Wikpedia article: Wikipedia contributors (2006). ORTF stereo technique. Wikipedia, The Free Encyclopedia. Retrieved 15:16, April 20, 2006 from http://en.wikipedia.org/w/index.php?title=ORTF_stereo_technique&oldid=49038742.
