Standards for noise measurement regarding machines and equipment.

The standards applicable for in situ measurement are:


engineering accuracy

survey accuracy

Emission sound
pressure level

ISO 11201
ISO 11204(always needs power measurement)
ISO 11205(tri-axial intensity measurement)

ISO 11202
ISO 11203(when specific test codes exists)

Sound power level

ISO 3744
ISO 3747(comparison method)

ISO 3746
ISO 3747(comparison method)

  • The emission sound pressure level is the A-weigthed sound pressure level at an operator or a bystander position
  • If a machine-specific harmonized noise test code exists this has priority over the general ones mentioned in the table above. Specific noise test codes refer to the general standards but they contain extra requirements about operating conditions. For large machines they sometimes contain a measurement set up with a reduced number of microphones.
  • For outdoor equipment within the reach of 2000/14/EC, the noise level at workplaces must be determined with harmonized standards. The sound power of this equipment must be determined using the requirements of the 2000/14/EC. This directive contains a set of noise test codes for this purpose.
  • All standards in the table above are EN-ISO (can be preceded by NEN- DIN- etc)
  • Engineering or survey accuracy is not always a free choice; the acoustical condition at hand limits the accuracy. For survey accuracy a K3A or K2A must be below 7 dB, for engineering accuracy K3A or K2A must be below 2 dB. K3A or K2A qualifies the room and depends on the ratio between the enveloping measurement surface and the total acoustic absorption of the room.
  • K3A is used in the ISO 11200 series – K2A is the equivalent in the ISO 3700 series.
  • For determination of the measurement uncertainty in some cases the sound power must be determined, even if only the emission sound pressure level has to be given.
    This can be the case in poor acoustical environments (small hall or a machine too close to a wall).
  • Uncertainty must always be determined or estimated and taken into account in every noise statement or other information to the (potential) client. (EN-ISO 4871). Uncertainty is typically 6 dB for survey accuracy and 4 dB for engineering accuracy. Lower uncertainty ask for higher measurement efforts, with more samples (machines) and in different environments.

List of harmonized standards for machine directive Some standards involving safety may contain noise test codes, without mentioning this in their title.