A method of generating a personalized sound system hearing profile for a user. A refrigeration system outlet allows the flow of supply air into the cargo container. The front ends of the side rails support a pair of front caster wheels. The elastic binding may extend at least partially along the length of the lower edge of the covering. A code pattern of such frames having a variable number of bidirectional predicted frames can be dynamically determined. The joint members 7 are each coupled to a back end of a corresponding one of extension frames 4.