Correct description in header.

examples/dynamics/beams/example_dynamic_beam1b_free_spectrum.m

 %% Example Beam1b
-% A one-dimensional cantilever beam composed of N finite beam elements with spring at tip
+% A one-dimensional cantilever beam composed of N finite beam elements
+% subject to initial conditions 
+% with visualisation of the resulting amplitude spectrum
 addpath([ '..' filesep '..' filesep '..' filesep ]);
 %% General properties
 L = 1.0;  % length of the cantilever