I've heard it in the past with fiber based papers. I do not hear it now from any of the fiber based papers I use, but then again I also stopped using acetic acid stop years ago and went to an (almost) odorless citric acid based stop. I don't know if the PH at working strength is similar though it should be, or if the change has anything to do with the lack of sound from current papers I use.

Humm..just read the above. I use Ethol LPD and Harman WT depending on the paper. The old fizzy days might have been with Dektol?