Introduction to the special issue on the effects of sound on aquatic life.

The effects of anthropogenic (man-made) underwater sound on aquatic life have become an important environmental issue. One of the focal ways to present and to share knowledge on the topic has been the international conference on The Effects of Noise on Aquatic Life ("Aquatic Noise"). The conferences have brought together people from diverse interests and backgrounds to share information and ideas directed at understanding and solving the challenges of the potential effects of sound on aquatic life. The papers published here and in a related special issue of Proceedings of Meetings on Acoustics present a good overview of the many topics and ideas covered at the meeting. Indeed, the growth in studies on anthropogenic sound since the first meeting in 2007 reflects the increasing use of oceans, lakes, rivers, and other waterways by humans. However, there are still very substantial knowledge gaps about the effects of sound on all aquatic animals, and these gaps lead to there being a substantial need for a better understanding of the sounds produced by various sources and how these sounds may affect animals.