Loud humming noise in bathroom

[bgo]

Just recently (last 3 days) when we come in after having been gone all day, there is a loud humming noise that can be heard throughout the house but can be traced to master bath (small closet for toilet). Flushing the toilet stops the noise. Any ideas and suggestions? Thanks

 

[Krow]

Your ballcock and/or flapper in the tank needs attention . Sounds like the water is running ever so slightly