http://www.k-wave.org/forum/topic/unexpected-sound-source-when-using-kspacefirstorder1d Support for the k-Wave MATLAB toolbox en-US Tue, 12 May 2026 23:34:30 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/unexpected-sound-source-when-using-kspacefirstorder1d#post-8576 Wed, 13 Jul 2022 18:41:21 +0000 bencox 8576@http://www.k-wave.org/forum/ <p>Hi PtL,</p> <p>There are two main problems. First you have placed your source in the absorbing PML. To avoid this use <code>source.p_mask(21,1)=1</code> as the PML is 20 grid points wide, or use the optional input pair <code>&#39;PMLInside&#39;, false</code>. </p> <p>Second, your time step is too long. Ideally the CFL number, the ratio of dt * sound speed / dx should be about 0.3. Setting the timesteps using <code>kgrid.makeTime(medium.sound_speed)</code> will sort that out.</p> <p>Also, you don't need the <code>source.p0</code> line.</p> <p>Best wishes<br /> Ben </p> http://www.k-wave.org/forum/topic/unexpected-sound-source-when-using-kspacefirstorder1d#post-8559 Mon, 04 Jul 2022 13:39:47 +0000 PtL 8559@http://www.k-wave.org/forum/ <p>clear variables;<br /> Nt=10240;<br /> dt=1e-4;<br /> Nx = 2048;<br /> dx = 1e-1; %when I change dx from 1e-1 to 1e-2, an unexpected sound appears<br /> kgrid = kWaveGrid(Nx, dx);<br /> medium.sound_speed =340; %[m/s]<br /> medium.density = 1.29; % [kg/m^3]<br /> source.p0=zeros(Nx,1);<br /> source.p_mask=zeros(Nx,1);<br /> source.p_mask(2,1)=1; % Define the real Sound Source's position<br /> m=zeros(Nx,1);<br /> m(100,1)=1;<br /> sensor.mask=m;<br /> kgrid.setTime(Nt, dt);<br /> source.p=100 * sin(2 * pi * 150 * kgrid.t_array);<br /> sensor_data = kspaceFirstOrder1D(kgrid, medium, source, sensor);</p> <p>%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%<br /> My codes are above, when I change dx from 1e-1 to 1e-2, at the end of x-axis there will be an unexpected sound source which send a sound wave to the real sound source. Is this a bug or I have something wrong?? </p>