http://www.k-wave.org/forum/topic/oscillation-in-pa-signal-from-point-source-in-heterogeneous-medium-2d Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 15:13:37 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/oscillation-in-pa-signal-from-point-source-in-heterogeneous-medium-2d#post-6132 Wed, 13 Sep 2017 17:20:48 +0000 Francis K J 6132@http://www.k-wave.org/forum/ <p>Hi Brad,</p> <p>Thanks a lot. It really worked well. </p> <p>Best,<br /> Francis </p> http://www.k-wave.org/forum/topic/oscillation-in-pa-signal-from-point-source-in-heterogeneous-medium-2d#post-5995 Mon, 19 Jun 2017 20:47:16 +0000 Bradley Treeby 5995@http://www.k-wave.org/forum/ <p>Hi Francis,</p> <p>I suspect it's because of numerical dispersion. I would suggest setting <code>medium.sound_speed_ref</code> to the sound speed in the background medium (it is set to the maximum sound speed by default). Note, if you do this, the simulation will no longer be unconditionally stable, and you will need to follow the stability criteria outlined in the manual. You could also use <code>checkStability</code>. </p> <p>Hope that helps,</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/oscillation-in-pa-signal-from-point-source-in-heterogeneous-medium-2d#post-5982 Tue, 13 Jun 2017 02:22:16 +0000 Francis K J 5982@http://www.k-wave.org/forum/ <p>I am trying to simulate a bi-concave acoustic lens in 2D by introducing a higher sound speed for the lens. Medium sound speed is 1500m/s, density 1000kg/m^3 and lens sound speed is 2590m/s and density 884m/s. A point source (smoothened to avoid aliasing) is used as the initial pressure. I observed that there are multiple oscillations in the PA signal generated from the point source. ie instead of a single N-shaped pulse there is an oscillation with gradually decaying amplitude. To confirm the signal is not from multiple reflections from the heterogeneous part of the medium (impedance mismatch), I detected the signal before it reaches the lens. However, the signal remains the same. To further verify other parameters of the simulation, I simply eliminated the lens (heterogeneous part of the medium) and the signal falls back to the expected PA signal ( as in photoacoustic Waveforms in 1D, 2D and 3D Example ). </p> <p>Please help me to understand what caused the oscillating nature of PA signal. And how to solve this problem? </p>