Pump "popping" noise

CaitS07

I did a quick search in google, but I'm having trouble with a popping sound coming from my pump and I've noticed I'm not feeling as empty. I changed the white valves as was suggested in the posts I saw, but I am still getting the sound. Is there something else I should be trying? TIA!

P.S. I have a PIS and a Symphony 

alijeff2313

Mine do this too. I have changed my valves and it hasn't changed. But, it also hasn't affected my output. I have been pumping for 4 months now, so I'm interested to see what people may say.