What Is Sound Masking & How Does it Interfere With an Animal's Life?

Whales are affected by sound masking.

Sound masking is the technique of using one kind of noise to mask or conceal another noise. It has beneficial applications, as where an artificial background of "white noise" is used to obscure obtrusive and unwelcome sounds. Inadvertent sound masking in the natural environment can, however, be a hazard to some animals.

Benefits of Sound Masking

Many of us have used noise reduction headphones, often in airplanes to drown out the dull drone of the engines. In the workplace, sound masking systems can be installed to reduce annoyance from intermittent, discordant and unpleasant sounds caused, for example, by machinery or conversations, music and other unwanted noises in open offices.

Hazard to Animals

Problems can arise when inadvertent sound masking takes place in a natural environment such as the ocean. Mammals such as whales and dolphins are equipped to make and hear sounds underwater. Water is a good sound conductor, and whales and dolphins have sensitive internal ears that can detect and distinguish the direction even of distant sounds. At least, they can do so when those sounds are not masked by the noises caused by human use of the ocean.

Sources of Aquatic Sound Masking

Dolphins find directions by clicking.

The most obvious source of human-produced sound in an ocean is engine noise from ships. A less obvious hazard arises from the use of sonar, for example by submarines, a method of establishing the location of other vessels by sending out pulsing auditory signals and detecting echoes. Sonar is an important navigation tool, developed originally for military use, but it is increasingly important in the commercial fishing industry where it is used to identify the location of schools of fish. The Natural Resources Defense Council reports that, by the Navy's own estimate, sonar pulses can travel hundreds of miles at a level of intensity which can effect the behavior of marine mammals.

Problems for Dolphins and Whales

Submarine sonar masks natural communication underwater.

Dolphins use a kind of natural sonar to find their way about the ocean. They make loud clicking noises, and can discern the location of objects by listening for echoes. Dolphins also make whistling noises, apparently for social purposes. Some whales make sounds for echolocation purposes, sounds which can travel underwater for miles. Human sonar devices, or other human-produced underwater sounds, can cause confusion and distress, in effect masking the sounds the dolphins and whales need to make and hear. It has been suggested by Earthwatch that sound masking is a cause of lost, stranded or beached whales.

Attacking the Problem

Efforts to reduce the hazard caused by the Navy's sonar training program have had limited success. In 2008, the U.S. Supreme Court upheld the importance of "military readiness" over the welfare of marine animals. Although the Navy is required to operate in compliance with environmental law, it has consistently applied for exemption where exemptions are available. In Europe, although the problem is acknowledged, protective measures have been taken by some nations. Given the perceived military and commercial importance of underwater navigation, there seems to be no easy solution to this human intrusion on aquatic life.

References

• "Whales"; Dan Greenberg; 2003
• "Interview with Ken Balcomb"; Earthwatch; undated
• Congressional Research Office: Whales and Sonar: Environmental Exceptions for the Navy's mid-Frequency Active Sonar Training
• European Commission Environment: Whales & Dolphins

Resources

• Natural Resources Defense Council
• Center for Whales Research