The microphone geometry

[jingxuan9862]

hello ! could you tell me the microphone geometry that used and how can i get the const float DOA[8][4] in C_DOA_BF ?

[PhanLeSon03]

Hi,

It is circle with diameter 52 mm.

DOA map are just the delay in sample for 4 couples (mic1, mic2) (mic3, mic4) (mic5, mic6) (mic7, mic8) in different angle.
It is calculated offline to reduce the computation effort in real-time.

[jingxuan9862]

thanks for your answer ! but I want to ask how can I calculate the DOA map offline? the angel is unknow.

[PhanLeSon03]

If we want to know 8 directions only (0, 45,...,315 degree) we can calculate in advance the delay for 8 directions and make a map. Once, we have 4 couples delay from mic-array, we can search in the map for the closest pattern. I have the simple matlab code for get the MAP:
c = 343; % m/s
D = 52 ; % mm
fs = 16; % sampling frequency KHz
numDir = 8; % number of direction
Angle = linspace(0,2pi-2pi/numDir,numDir);
theta = linspace(0,pi/2,4);
Map = zeros(numDir,4);
%Map = zeros(3numDir,4);
%for i = 1:3
% Map(i:3:end,1) = -(Dfs/c)*sin(pi/2 -Angle)sin(theta(5-i));
%end
Map(:,1) = -(Dfs/c)*sin(pi/2 -Angle);
Map(:,2) = circshift(Map(:,1),1);
Map(:,3) = circshift(Map(:,2),1);
Map(:,4) = circshift(Map(:,3),1);
display(Map)

[jingxuan9862]

thanks for your answer !
you assume that the sound wave is the plane wave and don't care the pitching angle ?
If I have six micrphones ( uniform distribution) , how can I transplant your project to this case ?