Published: 24 August 2022 at 09:30
VIEWPOINT: If you don't like noise, imagine how pets and other animals feel about it
From construction projects to busy roads, aeroplanes and railways, human noise is everywhere. It is an invisible cause of stress, posing serious risks to human health and wellbeing. However, noise also harms animals living in close contact with humans, in homes, farms and zoos.
Noise is a distracting, scary or physically painful sound. The impacts of noise upon humans 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 paper, we found a greater awareness and more understanding is needed into how noise harms pets, farm and working animals and zoo animals.
Research tends to measure how loud a noise 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 noise source, frequency (pitch), rate and duration can also impact how noise is experienced by a listener.
Great apes have similar hearing capabilities to humans, but the rest of the animal kingdom perceives noise very differently. Hearing ranges from very high frequency ultrasound (>20,000 Hz) echolocation in bats and dolphins to very low frequency infrasound (<20 Hz) in elephants. The hearing range of humans sits right between ultra and infrasound.
Some invertebrates such as hunting spiders detect sound from vibrations with their tiny leg hairs. It’s difficult to tell how sensitive an animal is to noise but what’s most important is whether noise in their environment is within their hearing range, rather than if the animal has a high or low frequency.
Due to a lack of research, we don’t know that much about how precisely noise affects animals but this is what we’ve learnt so far.
Loud noise can permanently damage lab rodents’ hearing. We can assume this exposure is painful because rats exposed to loud noise behave differently with and without pain medication. Findings in lab rodent studies can be generalised to other mammals but there are known differences in hearing ability across different animals.
Wild animals suffer chronic stress, fertility problems and change their migration routes in response to noise. Confined animals are often exposed to high levels of human-generated noise which they cannot escape.
Research shows noise causes confined animals pain, fear and cognitive problems. For example in fish, vibrations from extreme noise can damage the swim bladder which in turn impacts their hearing and buoyancy. Pain and fear are strong indicators of poor welfare.
Inaudible noise (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 impacts zoo primates.
One noisy event such as a local music festival or extreme weather can trigger long-term fear in animals. The link between noise and fear has been well studied in dogs using recordings of thunderstorms.
This kind of noise sensitivity, which affects up to 50% of pet dogs, is triggered by unexpected noises. It makes animals hide or seek human comfort. Farmed hens exposed to vehicle noise and even music also freeze in fear.