Measures Against Ventilation Noise – which tone frequencies are least and most annoying?

20 subjects were exposed to a tonal ventilaton noise, with the information to adjust the tone frequency at 40 dBA, to the lowest and highest annoying experiences. The adjusted frequencies were 58 and 380 Hz. The higher frequency was correlated to significant higher annoyance, discomfort and lower performance. The rated effort was higher but below the significant level of 5%. According to the investigation, lower tone frequencies are less annoying than higher. The dBA ratings thus may result in an overestimation of the annoying reactions in cases of low frequency tone components.