The tape is just to hold the packing in place when inserting the baffle into the muffler. I've even used masking tape! You actually want the tape to fail, as this will allow the packing to expand. If the packing is tightly compressed, it won't be as effective as a silencer. An absorption type silencer tends to reduce the higher frequency elements, or sharpness as Gordon stated.
The design of the baffle also can make a difference; the size /shape/number of perforations, and the length of the perforations in the tube. When you get the mufflers, pull them apart and see what you have to work with.
Here's a pic of the baffle from my bike, with a good portion of the 'glass burned out.