This part om ISO 11546 specifies laboratory methods for the determination of the sound insulation performance (insertion loss) of small machine enclosures.It applies to a total enclosure only and not to the individual panels from which the enclosure is made.NOTES1 Sound insulation for enclosure panels such as wall elements, doors, windows, silencers, etc should be measured in accordance with other relevant standards.2 Related standards concern noise-attenuation measurements of enclosures insitu (ISO 11546-2) and cabins (ISO 11957).The measurement methods specified in this part of ISO 11546 are based on International Standards in the series ISO 3740, ISO 9614 and ISO 11200 (see table 1). Depending on the method chosen, the sound insulation performance (insertion loss) of the enclosure is determined in terms of the reduction of sound power level or sound pressure level. Methods are given for measurements where the enclosure surrounds the actual sound source (machine). Where these methods are not practicable, alternative measurements can be performed using a reciprocity method (see defintion 3.11 and subclause 7.2) or an artificial sound source.This part of ISO 11546 is applicable without any restrictions to freestanding enclosures with volumes less that 2m3. If the actual sound source is used, the sound insulation performance of enclosures with volumes exeeding 2m3 can be determined provided that the requirements concerning maximum permissible volume in the standard used are fulfilled. The actual sound source method is applicable for any kind of enclosure design, for example enclosures fixed to the machine.When the reciprocity method or the artificial sound source method is used, the maximum volume of the enclosure is limited to 2m3. These methods are not applicable to close-fitting enclosures.