Sound was analysed over frequency, time domain and psychological acoustics. Key parameters to measure were loudness, tonality, roughness, fluctuation, and sharpness.
To meet the above objective meant development of new micro-motor technology, new impellor design and air channel control.
The resultant Sunon Super Silent HA series fan noise is less than 20 phon. 20 phon is the minimal level of sound pressure loudness that is discernible in daily living.
In raw noise level terms this means a 40 x 20mm HA fan has a noise level of just 12.8 dB(A), the 120 x 25mm is 29.6 dB(A).