The ultra sound relay is a credibly-neutral and permissionless relay—a public good from the ultrasound.money team.

A credibly-neutral relay only validates blocks against consensus rules as in enshrined proposer-builder separation.

Enshrined proposer-builder separation (PBS) is an in-consensus PBS without relays, removing relay weak censorship.

Weak censorship is mild transaction censorship which increases on-chain inclusion delay of censored transactions.

Censorship in X% of blocks yields 1/(1-X%) larger average delay. If X% = 80%, delay grows 5x from 12 sec to 1 min.

The relay operators abstain from searching and block building, and commit to self-cap the relay to 1/3 of blocks.