Just for your information:
it’s an empty pipe, which has holes to break the pipe resonances (standing acoustic waves within the pipe). The patches are for reducing the generation of further noise sources along the tail pipe. This design replaces a resonator.
The best way to test is covering the patches as mentioned (clamps, pieces of metal), no need to remove or cut. The result can be a booming noise at the pipe resonance frequencies. It might rather be noticed in the car than outside.
If you replace the muffler, you have to pay attention about the positioning of the patches. The position is related to the tailpipe’s total length, which is calculated from within the muffler (after the last perforation field) related to the standing acoustic waves within the pipe. Positions therefore are 50% and as far as I remember 75% plus one in between of the total tailpipe length (including the section inside the muffler).