Equipment noise reporting involves several descriptions of sound: A-weighted sound power for comparing equipment, emission sound pressure at specified user positions, and hearing-model metrics for sound character. The Ecma standards also address the publication and verification of declared values, and corrections for the background contribution within a measured level.
Sound power and sound pressure
The December 2025, 22nd edition of ECMA-74 specifies procedures for measuring and reporting noise emissions from information technology and telecommunications equipment. Its basic emission quantity is the A-weighted sound power level. The standard identifies this quantity for comparing equipment of the same type from different manufacturers, as well as for comparing different equipment.
Sound pressure supplies a position-specific description alongside that comparison quantity. ECMA-74 supplements sound power with A-weighted emission sound pressure determined at the operator’s position or at bystander positions. That pressure determination is based on ISO 11201, the basic noise emission standard named in ECMA-74. Equipment comparison and the operator or bystander position therefore both have a place in the standard’s description of noise emission.
Measurement versus declaration
The June 2025, 11th edition of ECMA-109 applies to information technology and telecommunications equipment. It addresses how acoustical and product information is published in technical documents or other product literature supplied to users. Publication can be electronic or in hard copy, and the information can be supplied by the manufacturer or declarer.
The standard also covers the method for verifying the noise emission values declared by manufacturers or declarers. Publication and verification are therefore both within its scope: the information presented to users, and the method for checking the declared noise values. This gives equipment noise declarations a subject of their own alongside the measurement and reporting procedures described by ECMA-74.
Tonality, roughness and fluctuation
ECMA-418 describes the Sottek Hearing Model and psychoacoustic metrics that depend on it. Part 2 is in its fourth edition, dated June 2025. The hearing model takes sound signals recorded according to ECMA-74 procedures as its input. The standard also lists Part 1 on prominent discrete tones, third edition, December 2024.
The model expresses specific loudness. Psychoacoustic models then use that specific loudness to express the strength of tonalities, roughness or fluctuation strength in the sound generated by information technology and telecommunications equipment. These are descriptions of sound character alongside the emission quantities used in equipment noise reporting.
Allowing for background noise
The December 2025, second edition of ECMA-425 describes a statistical background noise correction. Its purpose is to remove background noise contributions from measured noise levels. The measured noise emission or source level contains contributions from both the source and the background.
The correction is subtracted from that measured level to obtain the background-corrected source level: an estimate of the level radiated by the source or device under test. ECMA-425 presents its statistical approach as an alternative to the background correction in ECMA-74 and several other noise standards. The corrected result is thus a source-level estimate, with the background contribution accounted for by the correction.
How the descriptions fit together
The measured emission level described by ECMA-425 includes source and background contributions. Its estimate of the device’s own level is obtained through background correction. The quantity being described is therefore either the combined measured level or the estimated source level, depending on whether that correction has been applied.
For equipment comparisons, ECMA-74 identifies A-weighted sound power as the basic quantity; its supplementary sound-pressure levels refer to operator or bystander positions. ECMA-418 adds hearing-model descriptions of tonality, roughness and fluctuation strength. Together, these descriptions cover the equipment comparison, the sound at specified positions, the character of the equipment sound and the estimated contribution of the device itself.
The noise declaration concerns publication of acoustical and product information for the user and verification of the declared values. ECMA-109 covers those publication and verification methods for information technology and telecommunications equipment, including publication in electronic or hard-copy technical documents and product literature.