Hi All, On behalf of my U.S. federal government co-authors, we are pleased to share our recent publication titled "Categorizing Alternative Seismic Sources Based on Their Potential to Affect Marine Mammals". This article was recently published in a special issue on the Impact of Human Activities on Marine Life in the Journal of Marine Science and Engineering. The article is published as open access and is freely available here: https://www.mdpi.com/2077-1312/14/15/1379 Abstract: Seismic airguns generate high intensity noise that can affect marine life. Emerging alternative seismic sources offer promising opportunities to reduce acoustic impacts, yet their performance and integration into regulatory processes remain poorly quantified. We evaluated four recently developed alternative seismic sources to characterize their acoustic outputs, assess their relative impacts on marine mammals, and classify them within the tiered framework of the Operational National Mitigation Protocol for Geophysical Surveys—developed collaboratively by the National Marine Fisheries Service (NMFS), Bureau of Ocean Energy Management (BOEM), and Bureau of Safety and Environmental Enforcement (BSEE). The assessment included three ultra low-frequency (ULF) pneumatic sources (Tuned Pulse Source [TPS], Gemini Source, and Harmony) and a representative marine vibroseis (MV) system. Using NMFS auditory injury and behavioral disturbance thresholds alongside a new (60 s M-weighted sound exposure level) metric, we found that all alternatives produced lower 60 s energy and smaller auditory injury zones than conventional high impact airgun arrays. ULF pneumatic sources concentrate energy below 10 Hz, contributing to reduced exposure at ecologically relevant frequencies. TPS and the Gemini Source align with moderate impact tiers, while Harmony is more similar to higher impact sources. For MV systems, single and dual element configurations are placed in a lower impact tier, though an 18-element array requires further characterization before classification. Remaining uncertainties, including limited behavioral data and incomplete source characterization, highlight the need for continued empirical research. By offering a science-based framework, this work contributes to regulatory modernization, advances efforts to reduce ocean noise, and enables the responsible adoption of emerging “quieter” seismic technologies within a more consistent and streamlined approach Citation: Caplinger, J. E., Martin, M. J., Conrad, A. S., & Staaterman, E. R. (2026). Categorizing Alternative Seismic Sources Based on Their Potential to Affect Marine Mammals. Journal of Marine Science and Engineering, 14(15), 1379. https://doi.org/10.3390/jmse14151379 This publication represents a major milestone for the Center for Marine Acoustics (CMA) team, developed in partnership with colleagues at NOAA. Over the past several years, industry has advanced several alternative technologies to traditional seismic airguns. These new sources have reached commercial readiness and, in many cases, demonstrate improved geophysical performance. Our analysis shows that many of these technologies also substantially reduce acoustic impacts on marine mammals. This means their use can lower mitigation requirements and streamline permitting in certain contexts. We are excited to see how this work will support continued innovation, quieter oceans, and more effective regulatory decision‑making. We welcome your feedback or any questions. Have a great day! Cheers, Morgan Martin Morgan J. Martin, Ph.D. Marine Biologist Center for Marine Acoustics<https://www.boem.gov/center-marine-acoustics> [cid:86d6109f-1e3e-4803-bc7d-1c4082cc822c]