A common sound effect which makes use of the wah wah sound is the train whistle. As you play the following example, actually mouth the words wah wah at the same time as you use the hand wah wah technique. This will also prepare you for other harmonica techniques introduced later in the book.
This example combines the train whistle with a train rhythm. Another important thing to notice in this example is the symbol above some of the notes in the first line. This is called a fermata (or pause sign). It means to hold and pause the note before going on to the next one.