http://www.k-wave.org/forum/topic/impulse-response Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 00:47:39 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/impulse-response#post-7873 Wed, 07 Oct 2020 06:42:58 +0000 rainbowwhale 7873@http://www.k-wave.org/forum/ <p>1. Use source.p_mode = 'dirichlet'.<br /> You can find how it works in user guide. When you use 'dirichlet' command, value at source voxel is fixed at exact value as you set though, still not exactly what you want.<br /> 2. Consider a moving piston go forth and back. Forward moving makes compressive pressure wave and backward moving makes negative one. Change source from zeros to one is like moving forward and ones to zeros is like backward.<br /> 3. P^2/(rho*c) ? </p> http://www.k-wave.org/forum/topic/impulse-response#post-7871 Mon, 05 Oct 2020 20:38:11 +0000 benji 7871@http://www.k-wave.org/forum/ <p>the code above wasn't the correct one, this is - </p> <p>clear all; </p> <p>Nx=128;<br /> Ny=128;<br /> Nz=128;</p> <p>dx =0.0005; % grid point spacing in the x direction [m]<br /> dy =0.0005; % grid point spacing in the y direction [m]<br /> dz =0.0005; % grid point spacing in the z direction [m]</p> <p>kgrid = makeGrid(Nx, dx, Ny, dy, Nz, dz);</p> <p>medium.sound_speed=1500;<br /> medium.density=1000;</p> <p>[t,dt]=makeTime(kgrid,medium.sound_speed,[],2*10^(-5));<br /> kgrid.t_array=t;</p> <p>source.p_mask=zeros(Nx,Ny,Nz);<br /> source.p_mask(25,64,64)=1;</p> <p>source.p=zeros(size(t));<br /> source.p(10)=1;<br /> source.p=filterTimeSeries(kgrid,medium,source.p);<br /> sensor.mask=zeros(Nx,Ny,Nz);<br /> sensor.mask(25,64,64)=1;</p> <p>sensor.record={'p','u'};</p> <p>input_args = {};</p> <p>filename=['C:\Users\goral\Documents\Thesis\Matlab\benji\thesis book\try3.h5']; </p> http://www.k-wave.org/forum/topic/impulse-response#post-7870 Mon, 05 Oct 2020 20:05:59 +0000 benji 7870@http://www.k-wave.org/forum/ <p>Hi,<br /> I am attempting to simulate an impulse response of an acoustic channel. transmitter is omni-directional (practically a 0.5mmX0.5mmX0.5mm voxel, which a pulse pressure waveform is assigned to).<br /> Two questions arising from a basic simulation I ran (code attached at the bottom of the post) :<br /> 1. I defined a 1 voxel pressure source and located a sensor at the same voxel (source.p_mask==sensor. mask) . I Would expect the pressure recording at the source voxel to be exactly as the source waveform assigned to source.p. In practice, pressure recording is different than source pressure.<br /> 2. When placing sensors on-axis Infront of the transmitter, the pressure waveform seems to be a time derivative of the source waveform (while expected to receive a scaled version of the source waveform). Why is that?<br /> 3. What would be the best way to evaluate the source energy?<br /> Thanks ahead,<br /> Benji</p> <p>clear all; </p> <p>Nx=128;<br /> Ny=128;<br /> Nz=128;</p> <p>dx =0.0005; % grid point spacing in the x direction [m]<br /> dy =0.0005; % grid point spacing in the y direction [m]<br /> dz =0.0005; % grid point spacing in the z direction [m]</p> <p>kgrid = makeGrid(Nx, dx, Ny, dy, Nz, dz);</p> <p>medium.sound_speed=1500;<br /> medium.density=1000;</p> <p>[t,dt]=makeTime(kgrid,medium.sound_speed,[],2*10^(-5));<br /> kgrid.t_array=t;</p> <p>source.p_mask=zeros(Nx,Ny,Nz);<br /> source.p_mask(15,64,64)=1;</p> <p>source.p=zeros(size(t));<br /> source.p(10)=1;<br /> source.p=filterTimeSeries(kgrid,medium,source.p);<br /> sensor.mask=zeros(Nx,Ny,Nz);<br /> sensor.mask(25,40,40)=1;</p> <p>sensor.record={'p','u'};</p> <p>input_args = {};</p> <p>filename=['C:\Users\goral\Documents\Thesis\Matlab\benji\thesis book\try3.h5'];</p> <p>sensor_data=kspaceFirstOrder3D(kgrid, medium, source, sensor, input_args{:}); </p>