Equivalent noise level

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About the equivalent noise level , the noise floor of microphones is given.

There are various evaluation methods for self-noise that are designed to simulate the properties of hearing . There is what is known as the A-weighting according to DIN IEC 651. The values ​​appear to be a good 10 dB more favorable than the more critical measurement according to ITU-R (CCIR) 468-3.

Condenser microphones typically have higher output voltages; if the impedance converter is correctly designed (in the microphone body), the inherent noise has less of an effect. This intrinsic interference voltage is evaluated as noise voltage using standardized filters. The measurement result can be converted into the equivalent noise level using the microphone sensitivity.

For example, 15 dB equivalent noise level means that the inherent noise of the microphone is as strong as a noise with 15 dB SPL (Sound Pressure Level); see sound pressure level . The information must always contain a reference to the measurement method (such as CCIR or 'A'), see below.

A lower value for the equivalent noise level shows a lower level of inherent noise from the microphone. Today only the term equivalent noise level is in use and the earlier term "equivalent volume" is considered out of date. According to the standards IEC 268-1, DIN 45405 and DIN 45412, the intrinsic interference voltage is measured either with the filter in accordance with ITU-R 468-3 (CCIR, DIN 45405) with specification of the "quasi peak value" (QP) or with the filter in accordance with IEC 651 (DIN 45412) evaluated according to the A-weighting curve with indication of the effective value (RMS).

In the recording studio area, this evaluation is carried out according to CCIR, because the A-RMS evaluation with its approximately 11 dB lower value is not really considered to be correct in terms of hearing physiology. In the USA the easier to determine 'A' RMS values ​​are given, which also have a more favorable effect in marketing. The QP CCIR values ​​are more difficult to measure, also because the measuring devices according to this standard are rarer.

literature

  • Thomas Görne: Microphones in theory and practice. 8th, new, revised and expanded edition. Elektor-Verlag, Aachen 2007, ISBN 978-3-89576-189-8 .
  • Norbert Pawera: Microphone Practice . Tips and tricks for stage and studio. Technology, acoustics and recording practice for instruments and vocals. 4th, completely revised and expanded edition. PPV-Medien, Bergkirchen 2003, ISBN 3-932275-54-3 .
  • Stefan Weinzierl (Ed.): Handbook of audio technology. Springer Verlag, Berlin 2008, ISBN 978-3-540-34300-4 .
  • Hans Jörg Friedrich: Sound technology for media designers. Hear sounds - understand technology - design media. Springer Verlag, Berlin / Heidelberg 2008, ISBN 978-3-540-71869-7 .

Web links