edit VQ code blocks' tags

Enhancement/noise_enh.aux

@@ -0,0 +1,2 @@
+\relax 
+\gdef \@abspage@last{1}

Enhancement/noise_enh.tex

@@ -0,0 +1,32 @@
+\documentclass{standalone}
+\usepackage[utf8]{inputenc}
+\usepackage{tikz}
+\usepackage{verbatim}
+
+
+\usepackage{pgfplots}
+\DeclareUnicodeCharacter{2212}{−}
+\usepgfplotslibrary{groupplots,dateplot}
+\usetikzlibrary{patterns,shapes.arrows}
+\usetikzlibrary {fit} 
+\usetikzlibrary{shapes.geometric,positioning}
+\usetikzlibrary{bending}
+\pgfplotsset{compat=1.16}
+
+\begin{document}
+
+
+\begin{tikzpicture}
+    \node at (0,0) (in) {\parbox{1.1cm}{\centering Input signal}};
+    \node[draw] at (2,1.5) (vad) {VAD};
+    \node[draw] at (5,0) (est) {\parbox{1.5cm}{\centering Estimate noise}};
+    \node[draw] at (5,-1.5) (enh) {\parbox{1.5cm}{\centering Attenuate noise}};
+    \draw[->,very thick] (in) -- (2,0) -- (2,-1.5) -- (enh);
+    \draw[->,very thick] (in) -- (2,0) -- (vad);
+    \draw[->,very thick] (est) -- (enh);
+    \draw[very thick] (in) -- (3,0) -- (3.4,0.3);
+    \draw[very thick,->] (3.4,0) -- (est);
+    \draw[->,very thick] (vad) -- (3.2,1.5) -- (3.2,0.4);
+\end{tikzpicture}
+
+\end{document}

_toc.yml

@@ -4,7 +4,7 @@ root: index
 options:
   numbered: true
 chapters:
-- file: Preface/Preface.md
+- file: Preface/Preface_.md
   sections:
   - file: Preface/Using_this_document.md
   - file: Preface/authors.md