Noise

Noise Pollution in the Environment

Consistent, disruptive amounts of noise can be classified as noise pollution.

Large amounts of noise pollution can affect the surrounding environment, including living organisms.

Figure 1 – Look at this busy road. How many sources of noise can you spot? Unsplash

Scientific Principles of Sound

The World Health Organisation classifies sound as noise pollution if it exceeds 65 dB.

To put that figure into context, we need to understand the threshold and frequency of human hearing.

Threshold

The threshold of hearing for adults is 0 dB.

Sound is measured in decibels (dB). Unlike most units of measurement, it's logarithmic. It's based on orders of magnitude of ten, rather than a normal linear scale.

Let's use a volume of 10 dB as a reference. So:

• 20 dB is ten times louder than 10 dB

• 30 dB is one hundred times louder than 10 dB

• 40 dB is one thousand times louder than 10 dB

• 50 dB is ten thousand times louder than 10 dB

• etc…

How loud are everyday sounds?

Frequency

Sound is a longitudinal wave (a wave where all the particles of the medium vibrate in the same direction as the wave).

Frequency of sound waves is measured in Hertz (Hz). The typical frequency range of human hearing is 20 Hz to 20 kHz.

Types and Examples of Noise Pollution

You can find out more detail in our article Types of Noise, but for now, let's look at a summary.

Consequences of Noise Pollution: The Physical Environment

Loud sounds can damage the physical environment.

Since the invention of jet engines, acoustic fatigue has become a common yet frustrating phenomenon.

Stress commonly occurs at the branch or welding support of pipes. It's a particular problem faced by high-speed flying structures, such as aeroplanes.

Shock impacts are another concern. Vibrations caused by sound waves can cause structural damage to buildings.

Consequences of Noise Pollution: Living Organisms

As well as affecting physical structures, noise pollution can have an impact on living organisms.

Humans

One of the major consequences of noise pollution on humans is hearing damage. Exposure to loud sounds can result in tinnitus or deafness.

Other physical effects include stress (leading to increased blood pressure, contributing to heart disease), headaches, stomach problems, ulcers, and even heart attacks.

Psychological effects include anxiety, mood problems, sleep disorders, and behavioural changes such as increased aggression and trouble focusing.

Other Organisms

Exposure of livestock to noise pollution has been identified as a stressor. Chronic noise pollution leads to a variety of health problems in cattle, including issues related to metabolism, reproduction, digestion, immunity, and milk production. High levels of noise can impact livestock behaviour. Cattle become jumpy, fearful, and aggressive. Aircraft noise has been shown to provoke aggressive behaviour, cause disorientation, and impact foraging. In turn, this impacts weight gain and reduces productivity.

Figure 2 – Bells help farmers locate cows while they're grazing in fields, but cause a myriad of problems for the cows themselves. Unsplash

Noise pollution can disturb breeding birds, especially those who sing at a lower frequency. It's difficult for potential breeders to hear their songs through low-frequency noise pollution. This prevents mating decisions, and in some cases, prevents the females from being physically ready to breed.

It's not just birds' reproductive behaviours that are impacted – exposure to anthropogenic noise increases vigilance and reduces feeding behaviours.

Owls are particularly impacted by noise pollution. These nocturnal birds hunt by ear, and have a unique wing configuration to minimise flying noise. A study found that owls experience an 8% drop in feeding success per decibel increase in noise.

Bats, another nocturnal animal, use echolocation to 'see' and communicate.

Noise pollution disrupts echolocation, impacting the ability of bats to hunt and communicate. Bats have responded by altering their echolocation frequency, or migrating from noisy areas.

Figure 3 – Despite the phrase “blind as a bat”, the flying mammals can see. They lack the sharp colour vision of humans, but being nocturnal and having excellent echolocation skills, they don't need it! Pixabay

The Effects of Noise on Aquatic Life

We've learned how noise pollution can affect all organisms, but aquatic organisms are particularly at risk. Why? Well, marine mammals, such as whales and dolphins, rely heavily on echolocation to communicate, navigate, feed, and find mates.

Figure 4 – Dolphins echolocate by producing high-frequency clicks, which produce fast-travelling sound waves. They pick up the echoes from these sound waves using their jaws and large foreheads. They have special fatty tissues in these areas that channel the echoes towards their ears and brains! Unsplash

Since the Industrial Revolution, the seas have become loud. Ships, sonar devices, oil drilling, and seismic tests have caused a large amount of noise pollution. This disrupts echolocation, impacting the behaviour of marine mammals.

Sonar is a significant problem. Naval sonar devices are like the human version of echolocation; sending pulses of sound into the ocean to bounce off an object and return an echo, indicating its position. Sonar pulses can be as loud as 235 decibels! They can travel for hundreds of miles, interfering with echolocation. Sonar has significantly influenced the behaviour of endangered blue whales, leading to altered feeding patterns and mass strandings.

Seismic surveys have similar effects to sonar. Ships use air guns to shoot pulses of sound down to the ocean floor to search for oil or gas deposits. The sound blasts cause damage to the ears of marine animals and can cause serious injuries.

Reducing the Effects of Noise Pollution on Aquatic Life

Scientists have called for the reduction of noise pollution in the oceans. Strategies include:

• Collecting data to create sound maps, used to visualise areas of noise pollution and its influence on marine mammals

• Establishing international noise pollution standards

• Redesigning propellers

• Installing quieting technologies, such as sound-absorbing tiles, vibration isolators, and air compressors

• Place restrictions on sensitive areas

• Further research to gain a deeper understanding of the effects of noise pollution on marine life

I hope that this article has explained noise pollution to you. Remember that noise pollution is defined as harmful or annoying levels of noise. Excessive noise may seem irritating but harmless; unfortunately that's not true. Exposure to noise pollution can affect health and behaviour, especially for marine mammals.

^{1. Center for Hearing and Communication, Common Noise Levels - How Loud is Too Loud?, 2022}

^{2. Dale Purves, Neuroscience, 2001}

^{3. Dave Cutten, The top 10 animals with the best hearing, Hidden Hearing, 2021}

^{4. Iberdrola, Noise pollution: how to reduce the impact of an invisible threat?, Sustainability, 2022}

^{5. J. Tate Mason, Anthropogenic noise impairs owl hunting behavior, Biological Conservation, 2016}

^{6. National Geographic Society, Noise Pollution, 2022}