Popping sound and bubbles in extruded filament most probably is due to the filament is moist.

1) Preventing moist filament
Remove unused filament from the 3D printer, keep it in a ziplock bag with some silica gel bags. This will able to prevent the filament being moist too fast.

We suggest to get some ziplock bag from Daiso, it is pretty handy in this case.

2) Dry the filament
Some user use a food dehydrator to dry the filament.
We’ve never tried it yet, here are a guide that we found online on how hot and how long to dry the filament for your reference, the actual time and temperature still very depending on your food dehydrator.

Smimilar article:

https://www.filamently.com/blogs/all-blogs/humidity-a-silent-killer-of-pla-3d-printer-filament

 

Tell us how you prevent your filament from moist and how your dry them if they are moist in the comment.

Drying filament with food dehydrator

 

Filament Temperature Hours
PEEK 100° c 4 hours
PPS 95° c 3 hours
PA 80° c 2 hours
PC PBT 80° 2 hours
PC 80° c 2 hours
PMMA 80° c 3 hours
ABS 65° 2 hours
PETG 65° c 2 hours
PLA 50° C 1 hours
TPU 70° c 2 hours
TPE 70° c 2 hours
TPA 70° c 2 hours
WPC 65° c 3 hours