We're all familiar with noise – loud, unwanted sounds. We hear noise every day; other people's phones, sirens, and those roadworks that seem to have been going on forever. You probably don't give noise much thought, but it can actually be bad for your health! Long-term exposure to noise pollution can lead to stress, irritation, and heart problems. Remember to tell that fact your younger sibling next time you want them to be quiet!
Noise: Definition
You'll be familiar with the term, but let's give it a proper definition.
Noise is an unwanted sound considered loud and unpleasant.
Noise Pollution in the Environment
Consistent, disruptive amounts of noise can be classified as noise pollution.
Noise pollution is defined as harmful or annoying levels of noise.
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.
The threshold of hearing is the sound level below which a person's ear cannot detect any sound.
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.
Logarithmic scales are useful when there is a large range of quantities, such as earthquake strengths.
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?
| Sound | Volume (dB) |
| Breathing | 10 |
| Soft whisper | 30 |
| Conversation | 60 |
| Doorbell | 80 |
| Ambulance siren | 120 |
| Gunshot | 170 |
Frequency
Sound is a longitudinal wave (a wave where all the particles of the medium vibrate in the same direction as the wave).
In contrast, light (part of the electromagnetic spectrum) is a transverse wave – the particles of the medium vibrate perpendicular to the wave.
Sound frequency is the number of waves produced in one second.
Frequency of sound waves is measured in Hertz (Hz). The typical frequency range of human hearing is 20 Hz to 20 kHz.
Pigeons can hear ultrasound – i.e. sound that is too low for humans to hear. They can detect sounds as low as 0.5 Hz, enabling them to detect earthquakes, volcanic eruptions, and distant storms.
At the other end of the spectrum, moths can hear frequencies up to 300 kHz. It's theorised that they use their specialised hearing to escape bat predators, who communicate using high-frequency echolocation.
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.
| Type of Noise | Description |
| Aircraft Noise | Often disruptive near major airports, aircraft cause noise pollution in the form of engine noise and air turbulence. |
| Railway Noise | Those living near a railway may find themselves disturbed by rail noise, caused by wheels, braking, turbulence, and engine thrust. |
| Road Traffic Noise | Sources of road traffic noise include engines, tyres, and turbulence. |
| Industrial Noise | Industrial and manufacturing processes generate large amounts of noise through processes like drilling and blasting. Equipment is frequently noisy too, such as pile drivers, air compressors, and stamping machines. |
| Domestic Noise | Day-to-day appliances such as vacuum cleaners and washing machines create noise. Playing music at loud volumes can be classified as noise pollution. |
| Wind Power Noise | The sound of rotating wind turbine blades can cause noise pollution for those living nearby. |
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.
Acoustic fatigue is damage to piping caused by stress due to high levels of noise.
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.
When the Saturn V rocket launched, it released sound waves at a low to mid-frequency, causing shaking and rattling in windows miles away.
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.
Tinnitus is a condition where you perceive ringing or buzzing sounds in your ear, that don't come from an external source.
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.
In some countries, cows are equipped with a bell for several months. Wearing a bell leads to decreased head movements to avoid the generation of sound. This results in reduced feeding and ruminating behaviours, which in turn impacts growth rates. Other side effects include reduced saliva production, increasing the risk of rumen acidosis (a bovine metabolic disease) or changes in vagosympathetic balance (a feature of high blood pressure).
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.
Echolocation is a technique to determine the location of objects by using reflected sound.
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.
Noise - Key takeaways
- Noise pollution is defined as harmful or annoying levels of noise. To be classified as noise pollution, sound must exceed 65 decibels.
- Sound is measured using logarithmic decibels. The threshold of human hearing is approximately 0 decibels, and the frequency range of human hearing is between 20 and 20,000 Hertz. Noise pollution comes from a variety of sources: aircraft, railways, roads, industry, homes, and wind turbines.
- High levels of noise pollution can cause acoustic fatigue and shock impacts.
- In humans, noise pollution can result in hearing damage, health problems, and behavioural changes. In other animals, noise pollution can impact health, behaviour, reproduction, feeding, and echolocation.
- Marine mammals are particularly at risk from noise pollution due to their heavy reliance on echolocation. Sonar pulses, which can reach 235 decibels, cause serious disturbances.
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
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