Standardized noise measurement methods
Fan noise - Noise prediction and reduction methods

Standardized methods for measuring fan sound power have been developed by ISO since the early 2000s, based on the principles of the national standards that had previously applied.

In 2004, ISO/TC 117 Fans published the four-part standard ISO 13347, which presents methods for determining the sound power radiated by fans to the outside. In 2000, ISO/TC 43 Acoustics published standard NF EN ISO 5136 for measuring the sound power of ducted fans. A revision of the standard NF EN ISO 5136 was published in 2009.

The content of these two standards is summarized below.

Standards distinguish four types of fan connection, designated A, B, C and D (figure 26). For each type of connection, there are two or even three different sound power levels:

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