An audio signal processing device comprising: a first microphone configured to pick up audio and output a first audio signal; a second microphone configured to pick up said audio and output a second audio signal; a first frequency converter configured to convert said first audio signal to a first audio spectrum signal; a second frequency converter configured to convert said second audio signal to a second audio spectrum signal; and an operating sound estimating unit configured to estimate, based on the relative positions of a sound emitting member that emits an operating sound and said first and second microphones, an operating sound spectrum signal indicating said operating sound, by filtering said first and second audio spectrum signals using predefined filter coefficients determined from the fixed relative positions of the sound emitting member and the first and second microphones; wherein said sound emitting member is a driving device; said operating sound is a mechanical sound emitted at the time of operation of said driving device; said operating sound estimating unit is configured to estimate a mechanical sound spectrum signal that indicates said mechanical sound as said operating sound spectrum signal; said operating sound estimating unit is configured to filter said first and second audio spectrum signals so as to attenuate audio components arriving to said first and second microphones from a direction other than said driving device, thereby dynamically estimating said mechanical sound spectrum signal during operation of said driving device; and said audio signal processing device comprising: a mechanical sound correcting unit configured to correct said estimated operating sound spectrum signal for each frequency component of said first or second audio spectrum signal, based on the difference in frequency features of said first or second audio spectrum signal before and after the start of operation of said driving device; and an operating sound reducing unit configured to reduce said estimated operating sound spectrum signal from said first and second audio spectrum signals. a first microphone configured to pick up audio and output a first audio signal; a second microphone configured to pick up said audio and output a second audio signal; a first frequency converter configured to convert said first audio signal to a first audio spectrum signal; a second frequency converter configured to convert said second audio signal to a second audio spectrum signal; and an operating sound estimating unit configured to estimate, based on the relative positions of a sound emitting member that emits an operating sound and said first and second microphones, an operating sound spectrum signal indicating said operating sound, by filtering said first and second audio spectrum signals using predefined filter coefficients determined from the fixed relative positions of the sound emitting member and the first and second microphones; wherein said sound emitting member is a driving device; said operating sound is a mechanical sound emitted at the time of operation of said driving device; said operating sound estimating unit is configured to estimate a mechanical sound spectrum signal that indicates said mechanical sound as said operating sound spectrum signal; said operating sound estimating unit is configured to filter said first and second audio spectrum signals so as to attenuate audio components arriving to said first and second microphones from a direction other than said driving device, thereby dynamically estimating said mechanical sound spectrum signal during operation of said driving device; and said audio signal processing device comprising: a mechanical sound correcting unit configured to correct said estimated operating sound spectrum signal for each frequency component of said first or second audio spectrum signal, based on the difference in frequency features of said first or second audio spectrum signal before and after the start of operation of said driving device; and an operating sound reducing unit configured to reduce said estimated operating sound spectrum signal from said first and second audio spectrum signals.