There are many reasons that carpet will ripple up and form waves.  It happens a lot in high traffic areas and in rooms that consistently get temperatures above 85 degrees.  this homes ripples were caused by one reason, Improper Installation.  This carpet was only a few years old and it rippled at the walls and other areas because it did not get stretched properly during installation.  The only way to give carpet the stretch that it requires is to use a power stretcher.  MCR went out and power stretched the carpet in this home giving it the tension it needs as required by the manufacturer.