Hopefully this gets fixed in the next update.

I have been having the same issue since the last update. I, too, thought it was an issue with my headphones, but noticed their USB connection to PC wasn't having the same problem.

I troubleshooted for about an hour, trying everything I could think of. I used Gemini AI for assistance LOL. It recommended me to report it, and that's how I found this report. I haven't experienced this same issue on the PC version, so not sure if it's specific to the mobile build or not. Hope this gets fixed quickly, it's quite annoying!

Hey guys, the Firefox devs have found the problem & fixed it in the bug below: Bug 1947917 - Firefox android 135 audio crackling on any website while playing video or audio

The good news is the developers already figured out the problem, created a fix and uploaded it to the Firefox code. The audio fix is available in the Beta and Nightly versions now. For anyone on the main Firefox for Android release, you have to wait until Firefox 136 is released. It will be released on March 4th.

Hopefully this cures the annoying crackling/popping audio for everyone.