Scientists’ Comments on the Navy’s Assertion that 180 dB is a Safe

LFAS Exposure Level for Marine Mammals


K. C. Balcomb: "I conclude that the whales in the Bahamas incident were adversely and lethally impacted by sonar pings at received levels well below the 180 dB re 1 µPa considered safe for whales, and this was due to the aforementioned resonance problem. These pings were of much shorter duration (1/10th second) than the proposed LFA pings, I might add.

This sonar impact at received levels well below 180 dB is likewise well documented in the Greek incident reported in the NATO report SACLANTCEN M-133 (Annex G). The first whale to strand did so 40 km from the ship one hour after the acoustic trial commenced. If one takes into account how fast a beaked whale can swim (about 15 km per hour, maximum), it must have been at least 25 km from the ship when the first of its 238 four-second pings was transmitted! At that distance the RL was calculated by the Navy (NATO, Annex G) to be approximately 150 dB! The Bioacoustics Panel overlooked this important bit of evidence of received level for impact.

Dr. Dawson: "That these sounds used in the Bahamas and Greece caused problems over a wide geographical area appears to indicate that received levels much lower than 180dB (re 1µPa) are not safe."

"I am particularly concerned with the Navy’s conclusion (assumption) that LFA sounds are physically safe at received levels lower than 180 dB (re 1µPa). This position cannot be reached without 1) ignoring the lethal impacts now known for Cuvier’s beaked whales, and 2) extrapolating from very limited studies on a few species exposed to much lower levels than fully deployed LFA would produce. We cannot say that LFA sounds are safe at 180dB received level, or even at much lower levels."

Marine Mammal Commission & its Scientific Advisors: "…the available information is insufficient to make direct assessments of likely cause-effect relationships [between low frequency sounds in the ocean and the effects of those sounds on the hearing and biologically significant behavior of marine mammals.]"

"To establish a risk threshold the (Navy’s) scientific team would have had to have conducted a series of experiments demonstrating that the 180dB received level was the threshold for risk of harm from a single ping. No such experiments were done."

Dr. Whitehead: "The 180dB (re 1µPa) criterion for harm to marine mammals used in the FEIS is not accepted by the vast majority of scientists. The adoption of the 180dB criterion has no valid scientific basis (see my comments on LFA FEIS, O-021, also O-020, O-047). Instead a considerable and growing, body of knowledge shows that underwater sound may severely affect marine life at much lower levels. This includes the experiments on migrating grey whales (both with LFA and other playbacks), observations of beluga whales and sperm whales reacting strongly to distant noise sources (see Richardson et al., 1995), as well as the strandings of beaked whales in Greece and the Bahamas. In neither of these stranding events is it reasonable that all, or even many, of the animals involved received levels of greater than 180dB, yet they died. In the second case there is some evidence that this was a population-level phenomenon (see comments by K. C. Balcomb to J. Johnson of U.S. Navy).

In deriving their 180dB criterion, the Navy argues that Permanent Threshold Shift is the most serious consequence of underwater noise to marine mammals. The LFA FEIS does not specifically consider the possibility of non-auditory effects of the noise on marine mammals. Other mechanisms may be highly dangerous to whales, or other marine life. These include the resonance and rupture of internal organs and psychological effects causing stranding or other adverse behavior (such as too rapid ascents from depth). These could occur at lower levels than 180dB, and the evidence from the Greece and Bahamas strandings strongly indicates that they do."

Dr. Weilgart: "The Navy is selective in the research it chooses to cite and how to interpret that research. This is very poor science."

The Navy’s Environmental Impact Statement says on pD-1 of appendix D: "the lack of empirical data in the received level range of 155-180dB is an issue."

Prepared by Marsha L. Green, PhD – Ocean Mammal Institute

Back to Underwater Noise Pollution Fact Sheets

Back to OMI Home Page