diff --git a/figs/asd_noise_comp_bubble_aluminium.pdf b/figs/asd_noise_comp_bubble_aluminium.pdf
index 0ea5d0e..7f5de8d 100644
Binary files a/figs/asd_noise_comp_bubble_aluminium.pdf and b/figs/asd_noise_comp_bubble_aluminium.pdf differ
diff --git a/figs/asd_noise_comp_bubble_aluminium.png b/figs/asd_noise_comp_bubble_aluminium.png
index e6dbed7..cedf6e0 100644
Binary files a/figs/asd_noise_comp_bubble_aluminium.png and b/figs/asd_noise_comp_bubble_aluminium.png differ
diff --git a/index.org b/index.org
index 408a651..f8def89 100644
--- a/index.org
+++ b/index.org
@@ -232,6 +232,15 @@ The computed ASD of the two measurements are combined in Figure [[fig:psd_combin
  #+caption: Aluminium tube used to protect the beam path from disturbances
  [[file:figs/IMG-7864.JPG]]
 
+** Matlab Init                                             :noexport:ignore:
+#+begin_src matlab :tangle no :exports none :results silent :noweb yes :var current_dir=(file-name-directory buffer-file-name)
+  <<matlab-dir>>
+#+end_src
+
+#+begin_src matlab :exports none :results silent :noweb yes
+  <<matlab-init>>
+#+end_src
+
 ** Aluminium Tube and Bubble Sheet
 #+begin_src matlab
   load('./mat/long_test_plastic.mat');
@@ -276,6 +285,26 @@ The time domain measurement is shown in Figure [[fig:short_meas_time_domain]].
 #+end_src
 
 ** Nothing
+#+begin_src matlab
+  load('./mat/long_test_without_material.mat');
+  Ts = 1e-4; % [s]
+#+end_src
+
+#+begin_src matlab
+  x = detrend(x, 0);
+#+end_src
+
+The time domain measurement is shown in Figure [[fig:short_meas_time_domain]].
+#+begin_src matlab :exports none
+  figure;
+  plot(t, 1e9*x)
+  xlabel('Time [s]'); ylabel('Displacement [nm]');
+#+end_src
+
+#+begin_src matlab
+  win = hann(ceil(length(x)/10));
+  [p_3, f_3] = pwelch(x, win, [], [], 1/Ts);
+#+end_src
 
 ** Comparison
 #+begin_src matlab :exports none
@@ -285,6 +314,8 @@ The time domain measurement is shown in Figure [[fig:short_meas_time_domain]].
        'DisplayName', 'Alunimium + Bubble');
   plot(f_2(8:end), sqrt(p_2(8:end)), '-', ...
        'DisplayName', 'Aluminium');
+  plot(f_3(8:end), sqrt(p_3(8:end)), '-', ...
+       'DisplayName', 'nothing');
   hold off;
   set(gca, 'Xscale', 'log'); set(gca, 'Yscale', 'log');
   ylabel('ASD [$m/\sqrt{Hz}$]'); xlabel('Frequency [Hz]');