http://www.k-wave.org/forum/topic/high-frequencies-are-not-aliased-but-instead-compressed-together Support for the k-Wave MATLAB toolbox en-US Tue, 12 May 2026 22:34:52 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/high-frequencies-are-not-aliased-but-instead-compressed-together#post-7599 Sat, 13 Jun 2020 12:43:32 +0000 Bradley Treeby 7599@http://www.k-wave.org/forum/ <p>Hi gk7,</p> <p>Ok, it is likely related to spectral blocking then. Does your simulation have any absorption? If not, you could try adding some.</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/high-frequencies-are-not-aliased-but-instead-compressed-together#post-7585 Tue, 09 Jun 2020 00:18:41 +0000 gk7 7585@http://www.k-wave.org/forum/ <p>Yes, high frequencies (&gt; 95 MHz) appear when I set medium.BonA and they disappear when I don't set them. </p> http://www.k-wave.org/forum/topic/high-frequencies-are-not-aliased-but-instead-compressed-together#post-7567 Sat, 06 Jun 2020 18:11:29 +0000 Bradley Treeby 7567@http://www.k-wave.org/forum/ <p>Hi gk7,</p> <p>Just to confirm, the high frequencies &gt;95 MHz appear / disappear when you set / don't set medium.BonA?</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/high-frequencies-are-not-aliased-but-instead-compressed-together#post-7532 Wed, 27 May 2020 15:31:33 +0000 gk7 7532@http://www.k-wave.org/forum/ <p>Hi Bradley,</p> <p>I checked out the linear spectrum. As you suspected, it's flat except the main lobe at 1 MHz without high frequencies. How do I need to define the source to obtain proper results with nonlinear simulations? </p> http://www.k-wave.org/forum/topic/high-frequencies-are-not-aliased-but-instead-compressed-together#post-7515 Thu, 21 May 2020 11:18:00 +0000 Bradley Treeby 7515@http://www.k-wave.org/forum/ <p>Hi gk7,</p> <p>Could you try running your simulation under linear conditions (don't define <code>medium.BonA</code>) to see if you still see the high frequencies? It could be related to your source definition rather than the nonlinearity. You have a very flat spectrum before the high-frequency peak, which doesn't immediately look like spectral blocking.</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/high-frequencies-are-not-aliased-but-instead-compressed-together#post-7470 Sun, 03 May 2020 00:19:04 +0000 gk7 7470@http://www.k-wave.org/forum/ <p>I'm running the "Modelling Nonlinear Wave Propagation Example" in Matlab with a time varying source that produces linear sine sweep centered at 1 MHz and spanning 0.9 MHz. I want to see the higher order harmonics so I set up the time and grid parameters so that I have 674 MHz sampling rate and 101 MHz maximum supported frequency. When I look at the resulting spectrum of the sensor data, I see bunch of frequencies are squished around 95-101 MHz. Please see this link (<a href="https://imgur.com/a/71uxjbq" rel="nofollow">https://imgur.com/a/71uxjbq</a> ) for the spectrum. To my understanding, aliasing doesn't seem to explain this. I'd still expect a decreasing pattern in higher frequencies even if they were aliased. Am I missing something? What could the reason be? </p>