Marine vessels are mandated or requested to reduce speed to meet operational, economic, and conservation goals. Vessel speed reduction (VSR) is a key strategy in global efforts to reduce ocean noise. Many regional VSR programs incorporate underwater acoustic monitoring to assess reductions in underwater radiated noise (URN) from vessels. Drawing from North American VSR programs, approaches to measuring URN reduction are assessed and progress toward robust metrics, scalable methods, and integrative measures are documented. Improved alignment across programs is recommended across programs to achieve measurement comparability to advance VSR evaluation and contribute to global underwater noise reduction and sustainable shipping goals.