Went for a short freezing ride today, with the 12" x 12" section in.
If I get decent power out of this, I've succeeded. As others have noted with the PC4, idle is louder than higher revs. Once the bike is under way, noise is down enough that 1/2 throttle can be used in a quiet neighborhood. Even running next to a convertible.
The sound is low-pitched and smooth. I tried to get a video as I drove away, but seem to have a bad SD card... I'll post something to utube ASAP.
The only other consideration is durability. I suspect I may need to find something that uses thicker wire for long-term life. That would also reduce noise more than this tiny wire mesh I'm testing with.