http://www.k-wave.org/forum/topic/frequency-shift-due-to-attenuation Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 05:59:19 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/frequency-shift-due-to-attenuation#post-4748 Sat, 27 Sep 2014 18:22:25 +0000 aall 4748@http://www.k-wave.org/forum/ <p>Hi Brad,<br /> Sorry for the delay (we had a holiday), and thanks again for your reply.<br /> In order to measure the frequency shift, i simply do FFT on the sensor_data of one element, or FFT on the scan_line. Then I can see clearly the Gaussian is around 1MHz.<br /> I'll go over the articles you sent me.</p> <p>Almog. </p> http://www.k-wave.org/forum/topic/frequency-shift-due-to-attenuation#post-4739 Wed, 24 Sep 2014 12:00:29 +0000 Bradley Treeby 4739@http://www.k-wave.org/forum/ <p>Hi Almog,</p> <p>The absorption model is described <a href="http://www.k-wave.org/papers/2010-Treeby-JASA.pdf">here</a> and <a href="http://www.k-wave.org/papers/2012-Treeby-JASA.pdf">here</a>.</p> <p>I agree the result seems peculiar. How do you measure the frequency shift?</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/frequency-shift-due-to-attenuation#post-4738 Mon, 22 Sep 2014 22:20:25 +0000 aall 4738@http://www.k-wave.org/forum/ <p>Hi Brad,<br /> Thank you very much for your responding.<br /> What you wrote is what i got in the simulation result.<br /> I took in account the maximum frequency (which is around 9 MHz).<br /> I will run the simulation you recommended, but the thing is that we want to see the frequency shift, which supposed to be around 400 KHz.<br /> I think they may be differences between the attenuation model I know and the one in k-wave.<br /> i would like to know how it was implemented in k-wave? i.e. the attenuation as a function of: frequency, distance, alpha_power and alpha_coefficient.</p> <p>Thanks,<br /> Almog. </p> http://www.k-wave.org/forum/topic/frequency-shift-due-to-attenuation#post-4731 Mon, 22 Sep 2014 10:09:00 +0000 Bradley Treeby 4731@http://www.k-wave.org/forum/ <p>Hi aall,</p> <p>I'm not sure I completely understand your question. Do you mean that you transmit an ultrasound signal centred around 4 MHz, and then receive one centred around 1 MHz? What is the maximum supported frequency for your simulation? This is printed to the command line, or you can work it out by:</p> <p><code>f_max = min(medium.sound_speed(:))/(2*kgrid.dx)</code></p> <p>Do you get the same result if you make the simulation lossless by not specifying the absorption parameters?</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/frequency-shift-due-to-attenuation#post-4721 Thu, 18 Sep 2014 15:46:19 +0000 aall 4721@http://www.k-wave.org/forum/ <p>Hi,</p> <p>My simulation is based on the example_us_bmode_phased_array.<br /> The scattering region is located at 160mm from the transducer.<br /> The spectrum of the transmitted signal is shifted by 3MHz, far more than the expected (according to literature - hundreds Hz).</p> <p> The transmitted signal properties:<br /> ----------------------------------<br /> source_strength = 1e6; % [Pa]<br /> tone_burst_freq = 4e6/sc; % [Hz]<br /> tone_burst_cycles = 3;</p> <p> Medium properties:<br /> ------------------<br /> medium.alpha_coeff = 0.75; % [dB/(MHz^y cm)]<br /> medium.alpha_power = 1.05;<br /> % mediun.alpha_mode = 'no_dispersion';<br /> % medium.BonA = 6;</p> <p>Any suggestions?</p> <p>Thanks! </p>