A brief history of our understandings on underwater noise impacts to marine life and the evolution of its regulatory process in the United States

It has been long understood that elevated noise is detrimental to signal detection by the anti-submarine warfare community. However, it was not until the early 1970s that similar concerns were raised regarding marine life that utilize sound for various life functions. The 1980s saw some of the first studies on effects of noise from offshore oil and gas exploration and development on marine mammals in Arctic waters. Low-frequency sources for ocean thermometry research and submarine detection over ocean basins brought additional concerns in the early 1990s on potential impacts on marine mammals from intense sources. Around late 1990s, several ad-hoc noise levels were adopted as acoustic impact thresholds of marine mammals by regulatory agencies in the U.S. Several cetacean mass stranding events that were coincidental with the mid-frequency military sonar operations and the increased awareness of ocean noise pollution accelerated research in this field in the 21^st Century. Numerous studies on hearing sensitivity and noise induced temporary threshold shift or physical injuries on various marine animal taxa led to new sophisticated regulatory guidelines on assessing underwater noise impacts to marine life. In addition, recent understanding of soundscapes as environmental quality factors provides new perspectives on marine species and ecosystem conservation.