weird pipe noise after toilet flush
 

Just heard this weird sound last week after flushing downstairs toilet. It was the loud sound of rushing water through the main water line in the basement. Kind of a chug, chug noise until the toilet fills.
Had a plumber at our house this week to fix another problem, a busted outdoor faucet. Had him listen to the noise and he didn't think it was unusual (course, he'd never heard the "normal" sound). Then, I couldn't get the pipe to make the sound again while the plumber was there.
Odd thing for me, is it's only this one toilet that produces the rushing noise. Logically, that means it must be caused by this one toilet, right?
I'm not a plumber, not a DIY by any stretch. Just want this fixed.
Any ideas?

Test the pressure on the house, could be high pressure.