The Environmental Cost of Marine Sound Sources
conference paper
Cumulative acoustic exposure is used as an indicator for the risk of negative impact to animals as a consequence of exposure to underwater sound. The free-field energy of a single source, defined as the total acoustic energy that would exist in the source’s free field, is shown to be closely related to the total cumulative exposure added over a population of animals. On this basis, the free-field energy of an underwater sound source, referred to as its “energy cost”, is proposed as an indicator of its environmental risk. For otherwise the same conditions, the environmental cost so defined of a multi-beam echo sounder (frequency 100 kHz) is about 40 000 times less than that of a search sonar (1 kHz) of the same source level. In turn, the cost of the same sonar is about 300 times less than that of a pile driver of the same energy source level, implying that source level (or energy source level) alone is a poor indicator of environmental risk. The main reason for this is that source level takes no account either of the amount of space occupied by the sound once in the water, or of the time required for the sound to dissipate. The free-field source energy, which includes the effects of source directivity and decay time, is therefore useful as an indicator of the environmental cost of a marine sound source.
TNO Identifier
464519
Source title
Proceedings 4th International Conference and Exhibition on Underwater Acoustic Measurements - Technologies & Results - UAM 2011, 20-24 June 2011, Kos, Greece
Pages
703-710