Hi guys, is this noise normal?

Berkshire 2-8-4
https://www.youtube.com/watch?v=no7xUthuwVY&feature=youtu.be

k4 4-6-2
https://www.youtube.com/watch?v=L8V70vnO6tc&feature=youtu.be

The volume of noise is low but the frequency is very strange,
I use mrc prodigy, I reset the decoder Cv8-8 the noise continues, is this normal?
Thanks and sorry for the english.