Michelle Kennedy

There is something polluting our world. You cannot see it, but it travels thousands of miles and constantly surrounds us. Hard to pin down, it presents a threat like no other. With increasing technology and exploration both on land and in the sea, sound pollution is more prevalent than ever before. In addition to affecting marine life, sound pollution affects millions of humans living in crowded cities or near busy streets.

Sound pollution, also referred to as noise pollution, is considered to be “any unwanted or disturbing sound that affects the health and well-being of humans and other organisms.” Sound pollution is unintentional most of the time and regularly goes unnoticed by humans. Sounds are measured in units called decibels, and any sound exceeding 85 decibels can harm a person’s ears. Every day, however, people are exposed to sounds that surpass this limit. The World Health Organization (WHO) has acknowledged that noise, after air pollution, is the second-most dangerous environmental risk factor for humans. From subways and trains (90-115 decibels), to the wail of an emergency siren (120 to 140 decibels), to your lawn mower (90 decibels), humans are constantly engulfed by dangerous levels of noise.

Trains are a large source of sound pollution on land. Photo by Brett Sayles from Pexels

Impacting millions on a daily basis, prolonged exposure to noise or a one-time exposure to extremely loud sound can lead to Noise Induced Hearing Loss (NIHL). Of the four million people living in the US with hearing impairments, 25% of those are diagnosed as NIHL. Many adults living in noisy atmospheres also suffer from increased stress and high blood pressure. Additionally, noise pollution has a profound effect on children. Studies have shown that children who live and attend school in noisy areas suffer from sleep disturbances, decreased reading level, and an inability to concentrate.

But the severity of sound pollution does not stop at humans. Numerous studies have found that the once-quiet seas are being subjected to higher levels and unique types of sound, impacting many marine organisms. Today, the main contributors of oceanic sound include commercial shipping, defense-related activities such as sonar use, hydrocarbon exploration and development, and recreational activities. Though a lot of human interaction with the sea is at the surface level, sound waves can travel hundreds of miles in all directions from their original source. In the past decade, oceanic noise pollution due to ship traffic alone increased by about three decibels per decade. Just like humans, an increasingly noisy environment affects marine organisms as well.

Many marine mammals and fish rely on hearing as sound travels much farther compared to eyesight. Through the use of sound, marine organisms can communicate, mate, find prey, and navigate hundreds of miles for migration. When these functions are disrupted due to a noisy soundscape, individuals are at increased risk. This type of disruption is referred to as auditory masking, in which, “the perception of one sound is affected by the presence of another sound.” One organism in particular that is affected by auditory masking is the northern elephant seal. Studies show that the communication range between northern elephant seals is significantly lower due to anthropogenic noise. Another result of auditory masking is severe behavioral changes in marine mammals. Attempting to move away from noisy waters, mating grounds have shifted. Additionally, auditory masking leaves many organisms that rely on their hearing vulnerable to predatory attacks.

Besides auditory masking, anthropogenic noise can severely damage the hearing system of many organisms and even kill them. Certain fish, particularly the pink snapper, have a very limited acoustic threshold. Scientists have found that after being exposed to the high-frequency sounds produced by an air gun, pink snapper experienced either severe hearing damage or instant death. Not only are high-frequency sounds damaging, but prolonged exposure to low-frequency sounds can impair hearing in cephalopods.

While most of the noise pollution that occurs originates from interacting with the sea, coastal urbanization could greatly impact surrounding marine environments. Research shows that the 2019 Ultra Music Festival in Miami, FL, impacted fish in a nearby water channel. While air noise did not exceed 98 decibels, fish in the Bear Cut water channel experienced a four to five-fold increase in cortisol levels. Many low-frequency sounds associated with music are perceived by fish as a threat, and as a result increase their levels of cortisol, which is a stress hormone.

Today our world is being inundated with more and more sound. While humans have adapted to dangerously high levels of noise, marine organisms are suffering. While many do not know the severity of noise pollution, many do and argue the urgency of the problem. The good news, however, is that noise pollution is easier to reduce than, say, ocean acidification. Researcher Kerri Seger explains we should be “redesigning propellers and re-routing shipping lanes… we can make tangible changes.” Although the urgency of the sound pollution issue is still being debated, there is enough evidence of its harmful impacts to warrant action.

Noise: A health crisis on land and in the sea