Estimating the DOA with MUSIC - circular array

Hi everyone,

I am very new to this and am trying to obtain the Direction of Arrival (DOA) of my signal of interest, which is a heart sound. I have a circular array of 4 microphones and am trying to estimate the DOA using the MUSIC algorithm. This is what I have written, however I get this error below. Does anyone know how to resolve this and can please confirm that my method of using pmusic to obtain the DOA from 4 microphone outputs is correct? Please let me know if there is any further description I should add, it is my first time asking a question on this community.

Error using musicOptions

Options must be character vectors or real, numeric, scalar or vector values.

[spectrum, angles_est] = pmusic([signal1 signal2 signal3 signal4], num_mics, array_response_circular, angles);

%% Estimating DOA

num_mics = 4; % Number of microphones

radius = 4.5; % Radius of the circular array

d = 4.5; % distance between mics

signal1 = filtered_signal_array{2}

signal2 = filtered_signal_array{3}

signal3 = filtered_signal_array{4}

signal4 = filtered_signal_array{5}

% Define polar coordinates for the microphones

% theta = linspace(0, 2*pi, num_mics + 1);

theta = [0, pi/2, pi, 3*pi/2];

mic_positions = [radius * cos(theta(1:end)); radius * sin(theta(1:end)); zeros(1, num_mics)].';

c = physconst('LightSpeed');

fs = 44100;

lambda = c / fs; % Wavelength corresponding to 1 kHz

% Array response function for a circular array

array_response_circular = @(theta) exp(-1i * 2 * pi * d * (0:num_mics-1).' * sind(theta) / lambda);

angles = 0:1:360; % Specify the range of possible angles

[spectrum, angles_est] = pmusic([signal1 signal2 signal3 signal4], num_mics, array_response_circular, angles);

% Plot the spectrum

figure;

plot(angles_est, 10 * log10(spectrum));

xlabel('Angle (degrees)');

ylabel('Power/Frequency (dB/Hz)');

title('MUSIC Spectrum');

% Identify peaks to estimate DOA

[peaks, locs] = findpeaks(10 * log10(spectrum), 'MinPeakHeight', -20); % Adjust threshold as needed

estimated_DOA = angles_est(locs);

Answer 1

[Anay]

Hi Yui,

I understand that you are facing an issue while using the “pmusic” function to determine the Direction Of Arrival (DOA) of your desired signal. The issue you are facing is due to incorrect arguments passed to the “pmusic” function.

The error “Options must be character vectors or real, numeric, scalar or vector values.” arises because “array_response_circular” is a function handle and “pmusic” has no definition which accepts input in such format.

The “pmusic” function can be called in several ways by specifying different set of options. You can use the following command in the MATLAB command window to take look at the “pmusic” documentation for determining what options are the most optimal for your case:

>> doc pmusic

I hope this solves the issue!