They kind of sound like the same loudness depending on how your microphone is aimed but the 22 is deeper when you first start it and the 22 burbles more than the 18. At least that's how it sounded to me. More than likely they will sound the same in time. Check the PN on the resonators and suitcase and see if they are the same. I'm sure they would be but who knows? Look on the resonators for the 4 digit numbers that end in R and L.
That's what I put on per year just commuting to work. Its probably the only 2 hours a day that I get alone time. Its probably my favorite time of the day - just me and my D listening to some podcasts or good tunes.