A properly designed shotcrete composite wall system would certainly create a quiet atmosphere in the interior of the house. There are 3-D shotcrete wall systems on the market which use shotcrete on both the interior and exterior surfaces with a foam material in the center for insulation and vapor barrier. Attempting to do something like this to an existing structure would require a lot of analysis. Shotcrete is a method of placing concrete and adding shotcrete to an existing wall would significantly increase the weight of the wall and could overload the footings or impact other parts of the system. A structural engineer well-versed in residential construction should be consulted before attempting such a modification.