The invention discloses a constant width beam forming method based on an FIR filter, wherein a received
signal f (t, x) =[f(t, x0), ..., f(t, xm), ..., f(t, xM-1)] T of a
microphone array is processedthrough a beam forming method to obtain an output
signal which is shown in the description, wherein f (t, x) represents a sampled
signal of the
microphone array at a t time position of x, () T represents a matrix
transpose, m represents a
microphone index, wherein m=0,1,... M-1, M represents the number of
microphone array elements, xm represents the
array element positions corresponding to the mth microphone, and x=[x0, ... ,xm,... ,xM-1); N represents the order of the FIR filter followed by each microphone, the description represents the coefficient of the n-order FIR filter followed by themth microphone, the superscript * represents the conjugate, and Ts represents the
delay between adjacent filters. The method can enable the array to have the same
spatial response to input signals with different frequencies within the
main lobe width, and the beam forming device with approximately constant beam width and low
side lobe array response is designed by utilizing the symmetric properties of the FIR filter array and microphone uniform
linear array.