Humming pipes

Hi everyone. I searched the site and found a lot of great info on my humming pipe problem, but heres what I have so far.

About a month ago, my pipes started with an occasional soft hum while the hot or cold water was running in the kitchen sink and upstairs shower. I could make it stop by slightly running another sink to releave the pressure. But it started to get louder and made noise with the other sinks, so I searched this forum for advice.

I bled the pipes, and the humming stopped for a couple of days, but it came back. I ran the water and while it was humming, I turned off each sink/toilet angle stop one by one, but it didn't stop the humming. I changed the PRV(set at 60psi) and I thought it was cured, but it again came back 2 days later.

Could it be a loose pipe in the wall? But if it is a loose pipe, would it stop after bleeding the pipes and come back? Could it be a bad washer in the shower? Any other suggestions?

When it's happening, go to the toilets and shut the stop valves an see if the hum goes away.

Next time it happens go to the PRV and see if the sound is coming from there.

I turned off the toilet one by one and that didn't help. Also, the sound isn't coming from the PRV.

So last night, the humming was very bad. But around 2:00 am I heard a gurgling in the pipes and now this morning there is nothing.