Standard measurements use the A-weighted sound pressure level as a measured variable. In case of difficult measuring conditions@ sound intensity measurements are advantageous. This application is described in annex B. According to this standard@ measurements on transformers are made under no-load. If a transformer has a very low no-load noise@ the noise due to load current can also influence the sound level. Annex C specifies the measurement conditions for determination of the noise due to load current.
IEC 60551/AMD1:1995 history
1970IEC 60551:1987/AMD1:1995 Amendment 1 - Determination of transformer and reactor sound levels
1987IEC 60551:1987 Determination of Transformer and Reactor Sound Levels (Edition 2.0)
1970IEC 60551:1976 Measurement of transformer and reactor sound levels
IEC 60551/AMD1:1995 Determination of transformer and reactor sound levels; Amendment 1 was changed to IEC 60076-10:2005 Power transformers - Part 10: Determination of sound levels.
IEC 60551/AMD1:1995 Determination of transformer and reactor sound levels; Amendment 1 was changed to IEC 60076-10:2001 Power Transformers - Part 10: Determination of Sound Levels (Edition 1.0).