A signal feature extraction apparatus for extracting features of an input signal by filter bank analysis including a plurality of band-pass filters, assuming that a superscript H denotes transposition, λ is a positive constant, M denotes a number of the band-pass filters, L denotes an integer which a maximum value of impulse response length of the band-pass filters is 2L+1, m denotes each integer from 1 or more to M or less, k denotes each integer from -2L or more to 2L or less, z k denotes a column vector having |k| zeros as elements, x ( n) = [ x ( n + L),..., x ( n + 1), x ( n), x ( n - 1),..., x ( n - L)] H denotes an input signal vector having an input signal sequence at time n as elements, and h m = [ h m (- L),..., h m (-1), h m, h m (+1),..., h m] H denotes an impulse response vector having an impulse response sequence of an m-th band-pass filter as elements, the signal feature extraction apparatus comprising: an extended impulse response matrix generation part that generates an extended impulse response matrix H e expressed by a following formula H e = h ̅ 1, − 2 L,..., h ̅ 1,2 L,..., h ̅ m, − 2 L,..., h ̅ m, 2 L,..., h ̅ M, − 2 L,..., h ̅ M, 2 L using an impulse response sequence h m,k which is, when k<O, h ̅ m, k = h m − L − k,..., h m − 1, h m 0, h m 1,..., h m L, z k H H, and when k≥0, h ̅ m, k = z k H, h m − L,..., h m − 1, h m 0, h m 1,..., h m L − k H; an expansion coefficient calculation part that obtains an expansion coefficient vector ŷ ( n) by calculating a following formula y ^ n = arg max y ̅ n ‖ x ̅ n − H e y ̅ n ‖ 2 2 + λ ‖ y ̅ n ‖ 1 using the input signal vector x ( n) and the extended impulse response matrix H e where y ( n) satisfies x ( n) = H e y ( n); and a signal output part that outputs as an output signal at least one of expansion coefficients corresponding to a center impulse response vector h m,0 of the extended impulse response matrix H e of the expansion coefficient vector ŷ(n). assuming that a superscript H denotes transposition, λ is a positive constant, M denotes a number of the band-pass filters, L denotes an integer which a maximum value of impulse response length of the band-pass filters is 2L+1, m denotes each integer from 1 or more to M or less, k denotes each integer from -2L or more to 2L or less, z k denotes a column vector having |k| zeros as elements, x ( n) = [ x ( n + L),..., x ( n + 1), x ( n), x ( n - 1),..., x ( n - L)] H denotes an input signal vector having an input signal sequence at time n as elements, and h m = [ h m (- L),..., h m (-1), h m, h m (+1),..., h m] H denotes an impulse response vector having an impulse response sequence of an m-th band-pass filter as elements, the signal feature extraction apparatus comprising: an extended impulse response matrix generation part that generates an extended impulse response matrix H e expressed by a following formula H e = h ̅ 1, − 2 L,..., h ̅ 1,2 L,..., h ̅ m, − 2 L,..., h ̅ m, 2 L,..., h ̅ M, − 2 L,..., h ̅ M, 2 L using an impulse response sequence h m,k which is, when k<O, h ̅ m, k = h m − L − k,..., h m − 1, h m 0, h m 1,..., h m L, z k H H, and when k≥0, h ̅ m, k = z k H, h m − L,..., h m − 1, h m 0, h m 1,..., h m L − k H; an expansion coefficient calculation part that obtains an expansion coefficient vector ŷ ( n) by calculating a following formula y ^ n = arg max y ̅ n ‖ x ̅ n − H e y ̅ n ‖ 2 2 + λ ‖ y ̅ n ‖ 1 using the input signal vector x ( n) and the extended impulse response matrix H e where y ( n) satisfies x ( n) = H e y ( n); and a signal output part that outputs as an output signal at least one of expansion coefficients corresponding to a center impulse response vector h m,0 of the extended impulse response matrix H e of the expansion coefficient vector ŷ(n). an extended impulse response matrix generation part that generates an extended impulse response matrix H e expressed by a following formula H e = h ̅ 1, − 2 L,..., h ̅ 1,2 L,..., h ̅ m, − 2 L,..., h ̅ m, 2 L,..., h ̅ M, − 2 L,..., h ̅ M, 2 L using an impulse response sequence h m,k which is, when k<O, h ̅ m, k = h m − L − k,..., h m − 1, h m 0, h m 1,..., h m L, z k H H, and when k≥0, h ̅ m, k = z k H, h m − L,..., h m − 1, h m 0, h m 1,..., h m L − k H; an expansion coefficient calculation part that obtains an expansion coefficient vector ŷ ( n) by calculating a following formula y ^ n = arg max y ̅ n ‖ x ̅ n − H e y ̅ n ‖ 2 2 + λ ‖ y ̅ n ‖ 1 using the input signal vector x ( n) and the extended impulse response matrix H e where y ( n) satisfies x ( n) = H e y ( n); and a signal output part that outputs as an output signal at least one of expansion coefficients corresponding to a center impulse response vector h m,0 of the extended impulse response matrix H e of the expansion coefficient vector ŷ(n).