This is just an informational post, but feel free to comment if you have anything to add.
Some time ago I went through and tweaked the ini files of all my games to address issues like tearing/jerking and sound stuttering using various combinations of options in mame. One such setting that worked well with certain games was
refreshspeed 1
Without this setting, a game like Asteroids exhibits jerking motion, but with this setting Asteroids locks in at 97% speed, but runs very smoothly with no jerking and clean sound. At least it did so up through version .237. Recently I updated to version .242 and this setting now produces bad audio popping/crackling--not just in Asteroids, but in most all games which use this setting. After banging my head a while trying every combination of option to get it to work like .237, I finally noticed that the speed in .242 was averaging 98% rather than 97%, so on a hunch I removed the refreshspeed option and changed my settings to force refresh to 97% using:
speed 0.97
...and now Asteroids is back to running just as well as it did in .237. This seems like a regression to me, but at least there's a workaround, though it requires manually computing the appropriate speed of each game individually.
Just wanted to share this in case anyone was planning to update, or did update and found that their sound was being affected.