When we think about the cacophony of noise in the environment, we rarely consider military noise pollution and often overlook its toll on humans and animals. Throughout the military service, noisy equipment and processes expose all military personnel and servicemen to hazardous noise levels that pose the risk of ear damage or permanent hearing loss. The constant noises not only wreak havoc on our auditory systems but also affects wildlife in their natural environment, from disrupting their communication and hunting abilities to mating.
The Transition of Sound to Noise
Sound consists of waves or vibrations of air molecules from the source to the ear. It is described in terms of the loudness (amplitude) and the pitch (frequency) of the wave. The intensity of sound level is measured in the logarithmic unit of decibel, abbreviated as dB. It means it increases by the power of 10.
Though Hertz and decibels are two different units, a 0 dB can be said to have an intensity of 1000Hz. While humans can tolerate frequencies as low as 20 Hz up to 20,000 Hz, some animals can hear frequencies well beyond human range, up to 100,000 Hz. In general, small animals hear high frequencies and vice versa. However, birds and fish have comparatively smaller frequency ranges than mammals.
Sound can reach unsafe levels of noise in no time. Most people around the world are exposed to intense occupational noise levels. Even a study published in Royal Society Open Science claims that long-term exposure to low-frequency, inaudible sound levels can also damage the ear.
Prolonged exposure to low-level sound or brief exposure to intense noise can have severe physical, physiological, or psychological impacts on the human body. For animals, the anthropogenic sound frequencies overlap with the frequencies they use for communications, thus affecting the quality of life.
The sources of damaging noise in the military include weapons systems, jet engines, vehicles, aircraft, watercraft, communication systems, and industrial-type activities ( Noise and Military Service: Implications for Hearing Loss and Tinnitus, 2006 ). The military personnel may be exposed to continuous and/or intermittent noise from firearms, radio communicators, vehicle sirens, etc., depending on the activities.
The various sound intensities of common military equipment are as follows;
- Helicopter 105 dB
- Tank 115 dB
- Jet engine 140 dB
- M-16/Machine gun 150 dB
- Pistol/Rifle fire 157 dB
- Anti-tank missile 166 dB
- Grenade 164 dB
- Anti-tank gun 182 dB
- Explosions/IEDs 180 dB
- Heavy artillery 185 dB
Convert these riotous noise frequencies into Hertz and imagine the consequences they have on our hearing and wildlife.
Effects of Military Noise Pollution on the Environment
Noise pollution has become an environmental stressor and damaging for humans and wildlife alike. Chronic exposures to sound levels greater than 75–85 dB has affected 1.3 billion people globally. It is among the top 20 reasons for years lived with disability (YLD) in North America, Central Asia, and Southeast Asia.
The impacts of military noise pollution on humans have been recognized and addressed for decades. Scientific interest regarding the implications of military noise for wildlife has been intensified in past years.
Research has been conducted on how noise affects the behavior of a wide range of species. The effects are particularly evident among bats, songbirds, frogs, whales, and dolphins, which rely on vocal communication, songs, and grunts to contact or warn each other, attract mates, or source food.
In many areas, birds and animals are exposed to military noises at such great frequencies intensities than ever in their evolutionary history. Chronic noise levels affect their ability to locate their food sources, thus disrupting their energy budget, reproductive success, and survival ( Radle, 2007).
Noise affects 7 major taxonomic groups
A significant contribution in this regard is the meta-analysis of over 100 studies; published in Ecology Letters by Hansjoerg P. Kunc and Rouven Schmidt, from the School of Biosciences, Queen’s University in Belfast.
The study encompassed 109 species divided into seven major taxonomic groups as amphibians, arthropods, mollusks, birds, fish, mammals, and reptilians, spanning across terrestrial and aquatic ecosystems.
The study analyzed whether there is a difference in the physiological and behavioral response to noise among all groups and how much phylogeny contributes to this. The research provides comprehensive evidence that noise affects all taxonomic groups independent of phylogeny ( Schmidt, 2019).
Researchers claim that the actual effects of noise are far greater than what is statistically reported. And when you take into account the frequencies of the military’s noise, the effects aren’t necessarily similar to those generated by civilian activities. What is loud for us may be ear-shattering to a songbird, for example.
Noise is influencing the behavior of many wildlife species
Clamoring noise levels have adversely influenced wildlife that relies on acoustic cues for their life activities and communication. Anthropogenic noise masks the environmental cues the wildlife send off or scan for, thus threatening their survival.
One such example is fringe-lipped bats that use echolocation for hunting their prey. Due to noise pollution, they have to invest more energy and time in sourcing food.
Birds are also sensitive to noise levels. Research conducted and published by Manchester University in collaboration with Manchester Airport in The Journal of Animal Ecology highlights aircraft noise impacts on birds near the airport. The study found that chiffchaffs nesting near an airport are five times more aggressive in response to noise than other birds.
Noise has been able to drive significant evolutionary changes in the behavior of wildlife. Many songs birds, for example, urban great tits, nightingales, song sparrow Melospiza melodia, etc., are adapting to omnipresent noise levels by singing or calling at higher frequencies. Others, like European robins, have adjusted their timing for call-songs to coincide with the quieter hours of the day.
In contrast, fringe-lipped bats have adapted to hunt in noise using other sensory cues from frogs, i.e., detecting the ultrasonic echoes returning from the frog’s inflated vocal sac. Such evolutionary changes are also observed in mammals, amphibians, and insects: all of them struggling to survive in their noisy neighborhood.
Besides plastics, noise pollution is on the rise at sea. Plastic is not the only thing that’s lingering under the sea. There’s noise too. And it is affecting the life underneath.
Seals that inhabit within 50 km of the coast are becoming deaf when exposed to the underwater rumble/nuance of sonar use. Fish larvae that locate their homes following coral reef sounds are lost because of the shipping industry and sonar devices.
Whales and Dolphins also rely on echolocation for life-sustaining activities. Intense noise, up to 250 dB, from sonar devices used by the military to detect invader’s submarines, intervenes with marine life’s ability to echolocate. The deafening noise of military sonar is not only affecting the distribution and behavior of the species but has also been linked to the stranding of whales. In 2005, 34 whales of three different species became stranded and died in North Carolina due to Navy sonar training.
Current Military practices
While wildlife is struggling with the booming metropolitan noise, the use of Washington State’s parks for military training exercises poses additional stress.
The Navy SEALs secured a permit for training exercises in 28 state parks on January 28, 2021. The decision is objected to by the Whidbey Environment Action Network (WEAN) and is leading a statewide coalition called, “Not in our Parks.”
Training involves Navy SEALs landing on shorelines, climbing upland, and conducting covert surveillance of park visitors. However, state park staff claim that the EPA impact review concluded “ no significant adverse impact “ on the parks.
Analyzing the far-reaching implications of noise isn’t easy, for the sound levels can’t be evaluated using a single measurement unit. The decibel unit doesn’t take into account the frequencies of the acoustic signals wildlife communicate at. And the behavioral and physiological effects of wildlife are also entangled with other stress sources as winter, disease, predators, etc. There is a dire need to establish threshold levels of noise and preserve natural soundscapes through technology for the conservation of humans and wildlife.
Nonetheless, the studies provide significant evidence that military noise pollution must be considered anthropogenic environmental change and pollution. So far, compliance with acceptable noise levels is the best approach as noise is something that’ll go off if the source is turned down. Furthermore, we need more conscientious environmental impact assessments of military training as well as developing strategies for environment and wildlife conservation.
References:
Noise and Military Service: Implications for Hearing Loss and Tinnitus. (2006). (L. M. J. Larry E. Humes, Jane S. Durch Ed.): The National Academies Press.
Radle, A. L. (2007). The Effect Of Noise On Wildlife: A Literature Review.
Schmidt, H. P. K. a. R. (2019). The effects of anthropogenic noise on animals: a meta-analysis. Biology Letters. doi: 10.1098/rsbl.2019.064910.6084/m9.figshar
Originally published at https://www.conservationmadesimple.org.
