Fan control system and method for noise cancellation

A fan control system applied to N fans inside a computer system, comprising:

• a main microphone for generating a main audio signal;
• a control circuitry coupled to the main microphone and configured to calculate a basic frequency value according to a temperature inside the computer system, and continuously update a parameter by a known optimization algorithm according to the main audio signal;
• a wave generation circuitry for generating N square waves according to the basic frequency value and the parameter;
• and
• a number N of fan controllers coupled between the wave generation circuitry and the N fans for forming and transmitting N modulation signals to the N fans according to the N square waves and N tachometric signals from the N fans;
• wherein the parameter is one of a frequency variation and a set of phase differences;
• wherein the N square waves have the same frequency;
• and
• wherein the known optimization algorithm is Gradient Descent.