various input signal « k-Wave User Forum

Thanks Brad

I have a problem in the following code, for the rectangular pulse, i am getting unusual output pressure signal, i am running it to test for various kind of signal input. Can i apply similar technique for the chirp signal.
Here is my code for the rect as the input function.

clear all
close all
sensor_radius = 2e-3; %[m]point sensor kept at a distance of 2 mm from the centre of the source.
ball_radius = 1e-3; %[m]source is a spherical ball of radius 1 mm.
pulsewidth_min = 0.1e-6; %min width of the pulse which excites the source.

%-------------------------------------------------------------------------------
%create the computational grid
%-------------------------------------------------------------------------------
%makeGrid(Nx,dx,Ny,dy)

% create the computational grid
dx = 0.025e-3; % grid point spacing in the x direction [m]
dy = dx; % grid point spacing in the y direction [m]
PMLe = 25*dx; %[no of grid points for PML*dx]
grig_length = (2*sensor_radius)+(2*PMLe); % total grid length in a particular direction [m]
Nx = grig_length/dx; % number of grid points in the x (row) direction
Ny = grig_length/dx; % number of grid points in the y (column) direction
%the nyquist requires two point per wavelength is necessary if we need to take
% x_size instead of Nx (then look details in the page 28)
kgrid=makeGrid(Nx,dx,Ny,dy);
% to see maximum spatial frequency type kgrid.k_max(details in the page 28)
%see how kspace looks like %imshow(kgrid.k,[])
% to make faster computation, grid points in the form of 2^(power)

%--------------------------------------------------------------------------
%define the material property
%----------------------------------------------------------------------------

medium.sound_speed=1500;

%--------------------------------------------------------------------------------
%time array
%---------------------------------------------------------------------------------
% if we need to set the final time
%kgrid.t_array=makeTime(kgrid,medium.sound_speed,[],t_end]
time.dt = pulsewidth_min/10; % sampling interval[s]
time.total = 6e-6 + sensor_radius/medium.sound_speed; % Total simulation time or the time taken by the wave to reach the transducer[s]
time.Nt = ceil(time.total/time.dt); % No of time steps[points]
time.t_array = 0:1:time.Nt-1; %time array having Nt time steps
time.t_array = time.t_array*time.dt;
kgrid.t_array=time.t_array;
%----------------------------------------------------------------------------------
%define the source pressure(requires sourc.p_mask and source.p
%----------------------------------------------------------------------------------
%--------------------------------------------------------------------------------
%source.p_mask
%---------------------------------------------------------------------------------------
% source.p_mask = zeros(Nx, Ny);
% source.p_mask(Nx/5, Ny/2) = 1;

% create initial pressure distribution using makeDisc
disc_magnitude = 1; % [au]
disc_x_pos = Nx/2; % [grid points]
disc_y_pos = Ny/2; % [grid points]
disc_radius = 10; % [grid points]
disc_1 = disc_magnitude*makeDisc(Nx, Ny, disc_x_pos, disc_y_pos, disc_radius);
source.p_mask = disc_1;
%--------------------------------------------------------------------------------
%source.p for variable input signal
%---------------------------------------------------------------------------------------
pulse_width = [0.1e-6 0.2e-6 0.5e-6 1e-6 2e-6 4e-6];% array of the various pulse widths
% define a gaussian pulse source

for i=1:length(pulse_width)

% a=1e-6;
% b=a+pulse_width(i);
%source.p=rectangularPulse(a,b,kgrid.t_array);
source.p=rectpuls(kgrid.t_array,pulse_width(i));

%filter the source to remove high frequencies not supported by the grid
source.p = filterTimeSeries(kgrid, medium, source.p);

%--------------------------------------------------------------------------------
%define sensor
%-------------------------------------------------------------------------------
sensor.mask=zeros(Nx,Ny);
sensor.mask(Nx/5,Ny/2)=1;

%---------------------------------------------------------------------------------
%run simulation
%--------------------------------------------------------------------------------------
sensor.record={'p','p_final'};

sensor_data=kspaceFirstOrder2D(kgrid, medium, source, sensor);%,'PlotScale',[-10 ,10]);

%--------------------------------------------------------------------------
%results
%plot the final wave-field
%--------------------------------------------------------------------------
%
figure;
imagesc(kgrid.y_vec*1e3, kgrid.x_vec*1e3, sensor_data.p_final + source.p_mask + sensor.mask, [-1 1]);
colormap(getColorMap);
ylabel('x-position [mm]');
xlabel('y-position [mm]');
axis image;

% plot the simulated sensor data
figure;
[t_sc, scale, prefix] = scaleSI(max(kgrid.t_array(:)));

subplot(2, 1, 1), plot(kgrid.t_array*scale, source.p, 'k-');
xlabel(['Time [' prefix 's]']);
ylabel('Signal Amplitude');
axis tight;
title('Input Pressure Signal');

subplot(2, 1, 2), plot(kgrid.t_array*scale, sensor_data.p, 'r-');
xlabel(['Time [' prefix 's]']);
ylabel('Signal Amplitude');
axis tight;
title('Sensor Pressure Signal');

end

Kamal Jnawali

k-Wave

A MATLAB toolbox for the time-domain
simulation of acoustic wave fields

various input signal

Reply

k-Wave

A MATLAB toolbox for the time-domain simulation of acoustic wave fields

various input signal

Reply

A MATLAB toolbox for the time-domain
simulation of acoustic wave fields