[2] German Institute for Standardization, DIN EN ISO 3741, 2011
[3] German Institute for Standardization, DIN EN ISO 3744, 2010
[4] German Institute for Standardization, DIN EN ISO 3745, 2017
[5] German Institute for Standardization, DIN EN ISO 3746, 2011
[6] Lerch, Technical Acoustics, 2009
[7] Veit, Technical Acoustics, 2018
[8] Wolfram, Analysis of the generation mechanism of rotating tones in houseless centrifugal fans, 2009.