Active noise reduction system

An active noise reduction system of an IMC type, comprising:

• a canceling sound output device configured to output a canceling sound for canceling a noise;
• an error microphone configured to generate an error signal based on the noise and the canceling sound;
• and
• a controller configured to control the canceling sound output device based on the error signal,
• wherein the controller includes:
• a control filter configured to generate a control signal for controlling the canceling sound output device;
• and
• a secondary path filter that represents an estimation value of a transfer function from the canceling sound output device to the error microphone,
• the secondary path filter is configured to generate a canceling sound estimation signal based on the control signal,
• the control filter is configured to generate the control signal based on a reference signal generated based on both the error signal and the canceling sound estimation signal,
• the controller further includes a primary path filter that represents an estimation value of a transfer function from a noise source to the error microphone,
• the primary path filter is configured to generate a noise estimation signal based on the reference signal, and
• the secondary path filter and the primary path filter are configured to be adaptively updated based on a virtual error signal generated based on both the reference signal and the noise estimation signal.