From construction projects to busy roads, planes and railways, human noise is everywhere. It is an invisible cause of stress and poses a serious risk to human health and well-being. However, noise is also harmful to animals that live in close contact with people, in homes, farms and zoos.
Noise is a distracting, scary or physically painful sound. The effects of sound on people range from mild irritation to learning and memory problems, permanent hearing damage and heart disease.
Abnormally loud noise, such as at music concerts or construction sites, is controlled to protect human hearing. But noise is not regulated for other animals.
In our recent article, we found that there is a need for greater awareness and understanding of how noise harms domestic, farm and working, and zoo animals.
Research tends to measure how loud a sound is in decibels (dB). Decibels are easy to measure with a handheld device and form the basis of human health guidelines. But the type of sound source, frequency (pitch), speed and duration can also influence how sound is experienced by a listener.
Great apes have similar hearing abilities to humans, but the rest of the animal kingdom perceives sound very differently. Hearing ranges from very high frequency echolocation (>20,000 Hz) in bats and dolphins to very low frequency infrasound (<20 Hz) in elephants. The human hearing range is exactly between ultrasonic and infrasound.
Some invertebrates, such as hunting spiders, detect vibration sound with their tiny leg hairs. It’s hard to say how sensitive an animal is to sound, but the important thing is whether the sound in their environment is within their hearing range, not whether the animal has a high or low frequency.
What do we know?
Due to a lack of research, we don’t know much about exactly how sound affects animals, but here’s what we’ve learned so far.
Loud noise can permanently damage the hearing of laboratory rodents. We can assume that this exposure is painful because rats exposed to loud noise behave differently with and without pain medication. Findings in rodent laboratory research can be generalized to other mammals, but there are known differences in hearing ability in different animals.
Wild animals suffer from chronic stress, fertility problems and change their migratory routes in response to noise. Confined animals are often exposed to high levels of human-generated noise from which they cannot escape.
Research shows that noise causes trapped animals pain, anxiety and cognitive problems. In fish, for example, vibrations from extreme sound can damage the swim bladder, which in turn affects their hearing and buoyancy. Pain and anxiety are strong indicators of poor well-being.
Inaudible sounds (vibrations) can also hurt animals by physically shaking their internal body parts. Farm animals experience high levels of vibration during transport. Our research group at Anglia Ruskin University is investigating whether vibrations from construction work affect zoo primates.
One noisy event, such as a local music festival or extreme weather, can cause long-lasting fear in animals. The link between noise and fear has been well researched in dogs using recordings of thunderstorms.
This kind of sound sensitivity, which affects up to 50% of dogs, is caused by unexpected sounds. It causes animals to hide or seek human comfort. Farmed chickens exposed to vehicle noise and even music also freeze with fear.
Primates, birds and frogs can adapt to noisy environments in the short term by vocalizing louder, similar to raising our voices at noisy parties. But the long-term consequences of animals having to change their communication methods have not been studied.
Prolonged exposure to loud noise reduces learning and memory ability in laboratory mice. The link between cognition and anxiety in humans is complex, but in general, high levels of anxiety impair our ability to perform challenging tasks.
This could be similar in other mammals, but there isn’t enough research to be sure. Studying noise in zoos is difficult because it is difficult to control other factors, such as the weather and the presence of visitors.
How to help
If your pet is stressed by noise, there are several treatments available to calm or distract him, including synthetic pheromones and enrichment toys. But prevention is better than cure.
When caring for confined animals, pay close attention to human activities that produce sound (such as cleaning and gardening) and how the environment may reflect sound waves. Sound waves can be blocked and bounce off materials such as concrete, metal and glass, making the sound worse.
You can protect your pets during noisy events, such as thunderstorms and fireworks, by providing extra spaces to escape noise. Some soft furnishings such as pillows or blankets in a den help absorb sounds. A pile of blankets to crawl under, even without a den, will help block out the noise.
Better regulation is needed to protect animals from construction work and noisy events. Animals have no say in which construction projects or music concerts go ahead, but they can suffer the consequences.