A noise reducing device includes: an acoustic-to-electric conversion section for collecting noise and outputting an analog noise signal; an analog-to-digital conversion section for converting the analog noise signal into a digital noise signal; and a digital processing section for generating a digital noise reducing signal on a basis of the digital noise signal and a desired parameter. The device further includes: a retaining section for retaining a plurality of parameters corresponding to a plurality of kinds of noise characteristics; a setting section for setting one of the plurality of parameters as the desired parameter of the digital processing section; a digital-to-analog conversion section for converting the digital noise reducing signal into an analog noise reducing signal; and an electric-to-acoustic conversion section for outputting noise reducing sound on a basis of the analog noise reducing signal.

A noise reducing device includes: an acoustic-to-electric conversion section for collecting noise and outputting an analog noise signal; an analog-to-digital conversion section for converting the analog noise signal into a digital noise signal; and a digital processing section for generating a digital noise reducing signal on a basis of the digital noise signal and a desired parameter. The device further includes: a retaining section for retaining a plurality of parameters corresponding to a plurality of kinds of noise characteristics; a setting section for setting one of the plurality of parameters as the desired parameter of the digital processing section; a digital-to-analog conversion section for converting the digital noise reducing signal into an analog noise reducing signal; and an electric-to-acoustic conversion section for outputting noise reducing sound on a basis of the analog noise reducing signal.

From a first microphone, first microphone signals are received that represent first sound waves. From a second microphone, second microphone signals are received that represent second sound waves. In response to the first microphone signals, analog processing is performed to estimate noise in the first sound waves, and first analog signals are generated for cancelling at least some of the estimated noise in the first sound waves. In response to the second microphone signals, digital processing is performed to estimate noise in the second sound waves, and digital information is generated for cancelling at least some of the estimated noise in the second sound waves. The digital information is converted into second analog signals that represent the digital information. The first and second analog signals are combined into third analog signals for cancelling at least some of the estimated noise in the first and second sound waves.