NOS stereo system

The NOS stereo system describes a special microphone arrangement for recording sound in loudspeaker stereophony .

Microphones in NOS arrangement

This miking was developed around 1960 by sound engineers of the Dutch radio, known as the Nederlandse Omroep Stichting . Hence the name NOS .

Through a series of practical experiments, they found a stereo main microphone system that results in a fairly even distribution of the phantom sound sources on the stereo loudspeaker base as the direction of the auditory event ( sound incidence angle ), with an effective recording range of the microphone system of ± 40.5 ° = 81 °. This system was determined empirically with two small diaphragm microphones with cardioid characteristics. This resulted in a total axis angle which is angled outwards with α = ± 45 ° = 90 ° and has a microphone base of a = 30 cm.

In the formation of the respective frequency Hörereignisrichtung neutral act Inter Channel - level differences Δ L and the same direction Interchannel- time differences Δ t as loudspeaker signals together. This recording technique is called mixed stereophony or equivalent stereophony . Thus the intensity stereophony and the transit time stereophony are used at the same time . Using these signal differences is called equivalence .

Usually this special microphone system has to be put together by the sound engineer from two single small diaphragm microphones. Large diaphragm microphones should not be used for this because of the unbalanced directional characteristics at different frequencies.

It seems advisable to experiment with the two parameters axis angle α for Δ L and microphone base a for Δ t . A sound recording with a main microphone system is often supplemented by support microphones .

See also

• ORTF stereo system
• Distance law
• Decca Tree
• Ear spacing

literature

• Thomas Görne: Microphones in theory and practice. 8th edition, Elektor-Verlag, Aachen, 2007, ISBN 978-3-89576-189-8
• Michael Dickreiter, Volker Dittel, Wolfgang Hoeg, Martin Wöhr (eds.), "Handbuch der Tonstudiotechnik", 8th, revised and expanded edition, 2 volumes, publisher: Walter de Gruyter, Berlin / Boston, 2014, ISBN 978-3- 11-028978-7 or e- ISBN 978-3-11-031650-6

Web links

• The NOS stereo system - Directional localization for stereo loudspeaker reproduction as a function of the angle of sound incidence θ on the NOS microphone system - Nederlandse Omroep Stichting (PDF file; 332 kB)
• Comparison of some equivalent microphone systems - NOS - EBS - RAI - ORTF - DIN (PDF file; 134 kB)
• Comparison of the recording areas from the ORTF system and the NOS system (PDF file; 258 kB)
• Theory basics: Equivalence stereophony (PDF file; 347 kB)
• Visualization of NOS stereo microphone system - cardioid / cardioid - 90 ° 30 cm equivalence stereophony - SRA recording area