ECMA-425

This Standard describes a statistical background noise correction by which background noise contributions may be removed from measured noise levels.

The statistical background noise correction is an alternative to the legacy background noise correction found in ECMA-74 and ISO 7779, ISO 3741, ISO 3744, ISO 3745, and ISO 11201.

Background noise corrections are used to obtain the background corrected source level, which is an estimate of the level radiated by the source or device under test. The background corrected source level is obtained by subtracting the background noise correction from the measured noise emission or source level, which contains both source and background contributions.

The statistical background correction (SBC) is independent of and unaffected by measurement grade. No present or future standard should link the SBC to measurement grade since the SBC is applied in the same manner regardless of measurement grade, unlike the legacy background correction (LBC) whose caps vary by measurement grade according to the standard calling the LBC.

Relative to the legacy background correction , the SBC is often larger and provides lower background corrected measured source levels when steady backgrounds are close in level to the measured source. The SBC advantage applies to both low and high background levels for steady backgrounds, since the SBC depends on the measured source-background level difference and not absolute background noise level.

While the application of the SBC is independent of measurement grade, the SBC advantage over  often depends on measurement grade because  depends on measurement grade for background levels approaching the measured source.

The measurement of noise emissions generated by Information Technology and Telecommunications Equipment (ITT) is described in ECMA-74 and ISO 7779.