Silent payment addresses starts from sp1.
This is the first time i have seen the Silent payment topic, it's totally new for me.
I have no idea at all about how they work, but it looks like there is a lot of information about it, and the technical details are on the BIP 0352, i will leave the link for those who want to learn about it:
https://en.bitcoin.it/wiki/BIP_0352The address from silent payments is long as hell, we are talking about 116 chars. So, it is worth to learn all about this implementation.