Expanding wave starting with longer arc

Question

How can I obtain an expanding wave in tikz that starts with a longer arc?

The minimal example below indicates what I want. The first two arcs, which are slightly visible should be removed completely and programmatically. Actually, I do not want to overwrite them by some workaround.

Is there a option for expanding waves to obtain this?

\documentclass[]{scrreprt}

\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}

\usepackage{amsmath}
\usepackage{amsthm}
\usepackage{amssymb}

\usepackage{tikz}
\usetikzlibrary{decorations.pathmorphing, decorations.pathreplacing}

\begin{document}
    \begin{figure}
        \begin{tikzpicture}
            \draw[decoration={expanding waves,segment length=1.5mm, angle=20}, ultra thick, decorate] (0, 0) -- ++(1.2,0);
            \draw[decoration={expanding waves,segment length=1.5mm, angle=20}, ultra thick, decorate, white] (0,0) -- ++(0.3,0);
        \end{tikzpicture}
    \end{figure}
\end{document}

Note: In a earlier version of this question I used the snake tikz library, which is now deprecated.

Answer 1

It can not be done with expanding waves alone as there is no option for alt. start point. A new decoration could be defined, but it is much simpler to just use clip (only things within the clip path is drawn):

\documentclass[tikz, border=1cm]{standalone}
\usetikzlibrary{decorations.pathreplacing, patterns}
\begin{document}
\begin{tikzpicture}
\pattern [pattern=checkerboard,pattern color=black!30] (0,-1) rectangle (2,1);
\clip (3.5mm, -1) rectangle (2,1);
\draw[decoration={expanding waves, segment length=1.5mm, angle=20}, ultra thick, decorate, red] (0, 0) -- ++(1.2,0);
\end{tikzpicture}
\end{document}