Somewhere in the following link is an exhaust level comparing several loud Porsche’s (RS, RSR, 928, etc.). They recorded and charted their results with what looks like a proper SPL (dB) meter.
https://m.youtube.com/results?search_query=Porsche+exhaust+comparison
However, some readers might attempt to use the volume control on their phone, laptop or desktop speaker(s) to understand what they’re trying to convey. Unfortunately, trying to replicate 100-126 dBs might cause most speaker cones to hemorrhage, and most will avoid equipment and/or ear damage and not understand the exhaust note as recorded.
For more accurate referencing, suggest reproducing using a proper sound system with one of several free/low cost dB/SPL meter apps. Then, one can more accurately quantify the perceived loudness of an exhaust system instead of relying on terms such as, “loud”, “sporty”, “racy”, “aggressive”, “knarly” and “*****in”.
Some may have to demo to the spouse for ultimate approval 😬