Standard definitions for sound source levels in the ocean

Abstract

Recently, increased attention has focused on the use of sound in long-term ocean-acoustic experiments. The question being the determination of begin levels or the quantification of acceptable levels. This is an important consideration due to the increased use of higher power sound sources and our increased awareness of the effects of sound on mammals. Recent discussions and papers at the 126th Meeting of the Acoustical Society illustrate the confusion which exist with respect to characterization of acoustic source levels and has resulted in erroneous and misleading reports (i.e., see information from John R. Potter reported by Malcolm B. Browne, ‘‘Science Times,’’ New York Times, 19 Oct. 1993). This paper presents some standard definitions for the comparison of decibel levels with references of peak pressure, energy, or power. Frequency-dependent characteristics of oceanic noise sources shall be discussed and the relative importance of sound levels from air guns, surface ships, marine mammals, and other sources shall be placed in perspective. Finally these sources of sound will be further examined in light of the propagation effects found in both shallow waters and the deep ocean.