Sound quality aspects of small computer fans

Paper in proceeding, 2006

The noise from personal computers is generally characterized by their fan noises. These may operate at a constant speed or have speed control based on component or ambient temperature. In domestic environments, any noise is of concern if it is attention-grabbing enough to cause annoyance. With this in mind, two listening experiments were conducted. The first test was conducted as an investigation into the threshold of audibility for hearing the tonal component of a fan in its normal running mode in the presence of background noise. The second test determined the limen of perception for a tone ramping in frequency and level as a fan increases its speed. Surprisingly, the results indicate that, in the tested octave, reduced ramp rates decreased the threshold of perception. The experiments further show the limen of perception of the tones to be the same for slowly ramped and stationary tones, and response times seem relatively shorter for lower ramp rates.