Sound masking occurs when a loud sound obscures a quieter sound. Offices and other professional environments use sound masking to mitigate the effects of distracting noises. Anthropogenic sound in nature can potentially disrupt the habits of indigenous wildlife.

Sound Masking Effects Whale Calls

Noise from commercial ships, engines and military sonar equipment has a disorienting effect on whales. Larger whales communicate over vast distances underwater, and their calls can be disrupted by submarines broadcasting low-frequency sonar.

Anthropogenic Noise and Animal Behavior

Animals alter their behavior in regions heavy with anthropogenic noise. A 2004 study by Foote revealed that three killer whales lengthened the duration of the vocalizations in the presence of boat traffic. Female killer whales swim more rapidly in the presence of heavy boat traffic. Altering their behavior may induce stress and adversely effect their energy and nutritional levels.

Hearing Loss and Other Dangers

The UK's Whale and Dolphin Conservation Society claims that there is evidence that anthropogenic noise has caused hearing loss amongst dolphins and whales. Navy sonar and oil rigs are two high-ranking noise-polluters. Mother dolphins use a variety of auditory stimuli to keep track of their young. These sounds become masked by sonar and drilling, leaving young dolphins vulnerable to prey.

Effects of Sound Masking on Whales

Killer whales respond to frequencies between 1 and 100 kHz, their most sensitive range being 20 kHz (Szymanski, et al. 1999). Over time, in regions where killer whale populations see increasing boat traffic, the whales' population steadily decreases. Measured underwater noise from boat traffic usually falls between 10 to 90 kHz.

Incident in Brazil

In 2002, an inordinate number of humpback whales were stranded off the coast of Brazil during a survey for oil which caused intense sound pulses. Similar incidents were recorded two years earlier when a large population of melon-headed whales were stranded off the coast of Hawaii.

Solutions

The United States Navy has agreed to limit its use of low-frequency sonar, especially in areas with large whale and dolphin populations. The European Union has called for a drastic reduction and possible ban on low frequency sonar.

Source:

Analysis of the ability of vessel noise to mask killer whale (Orcinus orca) communication

The Defeaning Sound of the Seas