Disturbing the sound of silence

Imagine that you are forced to live in an apartment located right beside Interstate 5. You tolerate the noise, but your friends have to shout to be heard. Cars cruise past with bass systems so powerful that your windows shake and your ears hurt. What if your only other housing alternatives were next to other freeways?

This scenario is, of course, preposterous. We can move away in search of the coveted sound of silence. For many, however, noise is becoming a trap -- a disturbance that threatens far more than aesthetic sensibility.

Marine animals live in a noisy world, among a din that has risen sharply in recent decades. An article in the Institute of Acoustics Bulletin estimates that ambient noise levels rose 10 decibels between 1950 and 1975 -- that is, a doubling of loudness. Were Jacques Cousteau alive today, he would not be exploring a "world of silence."

Currently, 75,000 operating merchant vessels cross international waterways. One supertanker can generate noise at levels above 190 decibels; when you allow for the approximate difference between the ways that airborne and waterborne sounds are measured, this still equates to a commercial jet departing one meter from the listener.

Ships are the most prevalent source of human-generated noise, but they are by no means the only culprit. Air guns from offshore oil and mineral industries are contributors, as are the Navy's new active sonar system and acoustic deterrence devices from commercial fisheries -- all joining together to create a cacophony of sounds that marine life cannot escape.

Biologists generally agree that hearing is the primary sense of marine mammals. Many researchers believe that whales depend on sound to avoid predators like orcas, to communicate across great distances to pods and prospective mates, and to establish mother-calf bonds. Significant noise interference could threaten individual mammals or entire populations.

We know little about the points at which marine mammals experience permanent or temporary hearing damage. Most studies are conducted upon captive species; the data collected is extrapolated to estimate the hearing capacities of other species. This is a questionable method, as researchers admit. We know almost nothing about how marine animals hear -- or how our activities affect them over long periods of time.

One new technology may threaten many marine animals.

The Navy says that it needs low-frequency active sonar (LFA) to protect its ships from a quieter breed of diesel submarines that are not easily detected. LFA sends 215 db pings out from its system; the sound waves reflect off objects from hundreds of miles away. Many fear that the magnitude of the waves will harm marine mammals and other sea life.

The Navy claims that concerns about the threat to marine animals have been addressed through extensive safety precautions; these include stringent restrictions against operation within 12 nautical miles of coastline and requirements that the system shut down if marine animals are detected in the 1.2-mile zone surrounding the ship. But, alongside these precautions, the National Marine Fisheries Service temporarily exempted LFA sonar from the Marine Mammal Protection Act in July.

The Navy has taken steps to address the environmental problems that LFA sonar poses. Nevertheless, like other industries that operate on the ocean, it overlooks the larger picture.

No one knows what will happen to marine animals after continuous exposure to elevated noise levels. The LFA sonar system produces intense blasts of sound; when combined with noise from other human activities, we subject marine animals to a constant barrage.

The cumulative effects of noise pollution on humans are known: a woman who operates a lawnmower without earplugs for eight hours per day over a few years will suffer hearing loss. Researchers have begun to speculate that whales experience similar problems. In 1996, two sperm whales residing in a heavily trafficked area of the Canary Islands made no apparent efforts to avoid a collision with a cargo ship and were killed. Post-mortem studies revealed acoustic trauma in their inner ears.

A handful of studies are not enough, and the problem is severe. As trade channels between nations open up, greater numbers of ships will traverse international waterways. When other nations develop similar LFA systems, our security demands will collide head-on with the whales that get in the way. Research must be done before we implement new technologies, including LFA; the risks are too great.

The ears of marine animals may not capture public interest, but they should. We need healthy oceans -- they sustain the planet, keep climate cycles in check and feed countless humans and animals. Further increases in ambient noise will harm marine mammals and other forms of sea life, which could jeopardize the overall health of the oceans, and thus of the earth.

Partial solutions to the problem do exist. For example, "quiet design" options for ships are already used by militaries and could be tailored to fit private and commercial vessels. Resistance comes, of course, because the technologies are too expensive. Yet, if we continue to drill, ship and monitor the waters unheeded, the cost will be insurmountable.