Abstract During the last decade significant research has been performed on the possible impact of seismic surveys on marine life. Both fish and marine mammals have been studied. None of the studies have documented direct damage caused by the signals, but there may be a temporary behavior change out to a distance of a few kilometers. Many reports dealing with this issue do not treat the acoustic principles or the measurement of signal pressure levels in a consistent manner. Therefore it may be difficult to make direct comparisons between the results given in these reports. During the many years that I have worked with this topic, it has become clear that an understanding of acoustic principles is important for the assessment of what effect seismic surveys have on marine life. This abstract therefore have a more detailed discussion of seismic survey principles and the physics of sound than will be possible to give at the oral presentation.