Acoustic Perception of Irregularly Spaced Blades Fan

Psychoacoustics

For acousticians, noise reduction is not the unique issue considering fan noise. In applications where human beings are involved (work, domestic, medical), annoyance has to be considered when evaluating the impact of fan.
Blade passing frequency is well known to be a characteristic of fan noise. It is often considered as unpleasant because of its tonal characteristics. But what happens if blades are irregularly spaced?
Measurements have been performed on a test bench and on an earthmoving machine to compare noise levels and psychoacoustics criteria of fans with regularly or irregularly spaced blades. The paper presents the results obtained for these measurements.