squealing in pipes when toilet flushed

when one of my toilets is flushed, there is a whistling/squealing noise until the tank fills up. It doesn't happen anywhere else..just this one toilet. I am concerned , because this area (toilet plumbing) was part of a reroute when we had a leak in the foundation plumbing last year. It just started a couple days ago...and I cannot figure it out. What could cause this squealing?

Thanks so much!
Fix It Mom

Most likely the fill valve.

Cleaning or replacement is the answer here.

Constant air noise from tank

Hi ... wondering if I have a similar problem. Had a plumber replace all the insides of this toilet last December. Now, when the tank finishes filling,a constant steady noise remains. There's no water coming in ... sounds like air under pressure ... reasonably loud but not obnoxious. When I shut off the intake valve (on the wall) the noise stops. Is that the fill valve, too? Thanks.

noise

If the shut off valve is tight, then shut it off and put a pencil mark on the water level then come back in 5 min and see if the water level has dropped.

Sounds like there may be a slight leak through the flush valve causing the new ballcock to slightly open and causing a noise of some sort.