A method of installing trim rings to headliner trims systems in motor vehicles comprising a trim ring, a headliner, and a sonic horn and stack. The sonic horn vibrates to bond/weld headliner to trim ring. Energy directors can be added to facilitate bonding/welding process. Fasteners can also be added for attachment to the vehicle body. This bonding/welding of the headliner to trim ring creates a smooth, molded look for the trim ring and does so without gapping to or sliding within the headliner.