<![CDATA[Ïã¸ÛÁùºÏ²Ê¿ª½± 389-4:1994]]> /cms/render/live/en/sites/isoorg/contents/data/standard/02/24/22496.html Ïã¸ÛÁùºÏ²Ê¿ª½± standards and projects Ïã¸ÛÁùºÏ²Ê¿ª½±.org 60 /modules/isoorg-template/img/iso/favicon/red/favicon1.ico http://www.iso.org/ <![CDATA[Ïã¸ÛÁùºÏ²Ê¿ª½± 389-4:1994]]> <![CDATA[Ïã¸ÛÁùºÏ²Ê¿ª½± 389-4:1994 - Acoustics — Reference zero for the calibration of audiometric equipment — Part 4: Reference levels for narrow-band masking noise]]> /cms/render/live/en/sites/isoorg/contents/data/standard/02/24/22496.html /cms/render/live/en/sites/isoorg/contents/data/standard/02/24/22496.html 2021-01-29