What could cause this noise?

[argh]

After replacing an original fill valve with a new TSU99A.XR, all was well until I noticed on very rare occasion, a faint water noise when the toilet is not in use. The fill tube is installed above the overflow pipe (similarly to how it was previously) and all seems to be dry on the floor. The toilet's performance hasn't changed, other than the new noise. What could be the issue?

An audio recording of the noise: https://drive.google.com/file/d/1fi3nsZO51ndIjViuVTDJrYyXGgDES41C/view?usp=sharing

 

[Breplum]

Bad gasket on the fill valve. The float cup has a black rubber washer that may be imperfect.
Request replacement from the mfr. Of course, maybe the cap. Not a fan of those Korky type fill valves.

 

[Sponsor]

 

[Fitter30]

Water level correct? Might want to lower it just a little just for a try.