Follow-up: Noise Pollution
In my previous blog post, I had briefly covered the detrimental impacts of the noise pollution produced by F1 races. While F1 is not the only noise-polluting sport, today’s blog entry is not meant to identify all instances of noise pollution in sporting events. Rather, I will be focusing on noise pollution itself – what it is, what causes it, and its differing impacts on wildlife and humankind.
Let’s start with the definition of noise pollution. It is generally defined as any unwanted sound that has a negative impact on the well-being of humans and/or any other organisms (Chandrappa & Das, 2021; Mohamed, 2021). There are 2 things to note from this definition. The first is that it does not discriminate against any sources of noise. Thus naturally-occuring sounds, such as waterfalls or thunderclaps, also count as sources of noise pollution. Second, this definition does not define any concrete threshold for when sound becomes noise pollution. Rather, it is entirely subjective. This essentially means that any sound of varying intensities and duration (e.g. a radio blasting music at full volume, snoring, or even wildlife mating calls) may be perceived as noise pollution depending on the individual. Nevertheless, countries often attempt to set their own legal standards for the regulation of noise emissions, though standards often differ from region to region (see Figure 1 for the variation of permissible noise levels in India), and are often difficult to enforce (Kalawapudi et al., 2020).
Figure 1: Singh and Davar (2004) summarises the permissible ambient noise levels (with no specified duration) as set by the Indian government in 2002. These regulations have not been updated since then, though the extent of the area covered by each category has been continuously updated (Kalawapudi et al., 2020). Note that the permissible noise levels varies both spatially and temporally, and do not single out any particular sources of noise. Are the economic activities that take place in the Industrial and Commercial areas during daytime a good enough justification for the heightened levels of permissible noise? Such regulations are telling of governments’ priorities and a reflection of their attempts to balance economic development and an “acceptable” or even normalised level of pollution.
Apart from focusing only on the volume of noise pollution (as typically measured in decibel (dB)), what authorities often miss out is the pitch (as typically measured in Hertz (Hz)). The diversity in hearing ranges of species could mean that some noises are imperceptible to some, and yet a major disturbance to others (Slabbekoorn, 2019; see Figure 2). Therefore, not all wildlife may be affected equally by the same source of noise pollution.
Figure 2: An excerpt from Polagye and Bassett’s (2019) illustration of commonly-emitted anthropogenic marine noise frequencies (in grey), and the range of hearing frequencies found in selected marine taxa (in orange). From this we can see that an identified source of noise pollution does not affect all wildlife equally – the high-frequency noises emitted from hydrographic sonars, for example, may have significant behavioural impacts on dolphins, and negligible impacts on sea turtles. Nevertheless, the relatively limited amount of data available on the hearing sensitivities of marine species might mean that we simply remain unaware of how extensive the damage caused by high or low-frequency noise can be.
In general, however, humans and wildlife that are affected by noise pollution will experience a series of physiological and/or behavioural changes (see Figure 3). Though the most severe physiological impacts (such as permanent hearing loss or even death) are experienced by organisms that are highly-sensitive to the intensities and frequencies of loud and nearby noise sources, moderate and prolonged noise exposure is likely to result in behavioral changes on far more individuals (Chahouri et al., 2022). In particular, the notable issue of auditory masking, whereby the “perception of one sound is affected by the presence of another sound” (ibid., p.5), can severely hamper the ability of wildlife that utilise echolocation for navigation, communication, and prey-detection. In order to adapt, such wildlife might adjust either the duration (as seen in humpback whales), repetition, or amplitude (as seen in greater horseshoe bats) of their vocalisations (ibid., Slabbekoorn, 2019; Wang et al., 2022).
Figure 3: Slabbekoorn (2019) provides a useful summary of the potential impacts of noise pollution on wildlife and humans in relation to the proximity of the noise. Exposure to intense sound at the source may result in physical damage (in red), while the effects of moderate sound exposure at a greater distance are represented in yellow and beige. Though the effects of the latter may seem minor in comparison, Slabbekoorn (2019, p.2) warns that these changes in individual specimens have the “potential to accumulate to population-level problems or ecosystem shifts”.
In cities, environmental (in)justice may also be embedded within the spatial distribution of urban noise pollution. Preliminary research has shown that those of a lower socio-economic status are more likely to be exposed to higher and more sustained levels of noise, which, combined with a greater health vulnerability (also directly correlated with a lower socio-economic status), could mean that it is the poor who feels a disproportionate burden of urban noise pollution (Dreger et al., 2019). Though more research needs to be done in this area to concretely ascertain the inequalities involved in noise pollution, such findings are worrying.
Identifying the causes and impacts of noise pollution, however, is just the start. The management of noise pollution is also an incredibly challenging task (as with managing all nonpoint-source pollution). It might seem straightforward to set a blanket noise emission cap on certain areas (see India’s example in Figure 1), but establishing a “safe” level of noise pollution is tricky. Countries may do well by referring to legitimate and well-researched guidelines, such as those set by the World Health Organisation (European Regional Office) in 2018. Such regulations will then necessarily have to be enforced strictly for it to be effective (Kalawapudi et al., 2020). The situation is more complicated in marine environments, especially out in international waters where underwater noise remains unregulated by international or national law (Markus & Sánchez, 2018). Efforts to tackle marine noise pollution will then have to be done at the international scale, akin to the joined efforts to combat transboundary air pollution (see: the UNECE Convention on Long-range Transboundary Air Pollution). It won’t be easy, but it is time to start seriously tuning down noise pollution.
References:
Chahouri, A., Elouahmani, N., & Ouchene, H. (2022). Recent progress in marine noise pollution: A thorough review. Chemosphere, 291(2), 132983.
Chandrappa, R., Das, D.B. (2021). Noise Pollution. In Environmental Health – Theory and Practice. Springer, Cham.
Dreger, S., Schüle, S. A., Hilz, L. K., & Bolte, G. (2019). Social inequalities in environmental noise exposure: a review of evidence in the WHO European region. International Journal of Environmental Research and Public Health, 16(6), 1011-1026.
Markus, T., & Sánchez, P. P. S. (2018). Managing and regulating underwater noise pollution. In M. Salomon & T. Markus (Eds.), Handbook on marine environment protection: Science, impacts and sustainable management (pp. 971-995). Springer, Cham.
Mohamed, M. (2021). A study of noise pollution and impact on human health. International Journal of Multidisciplinary Current Research, 9, 610-614.
Kalawapudi, K., Singh, T., Dey, J., Vijay, R., & Kumar, R. (2020). Noise pollution in Mumbai Metropolitan Region (MMR): An emerging environmental threat. Environmental Monitoring and Assessment, 192, 1-20.
Polagye, B., & Bassett, C. (2020). Risk to Marine Animals from Underwater Noise Generated by Marine Renewable Energy Devices. In A.E. Copping and L.G. Hemery (Eds.), OES-Environmental 2020 State of the Science Report: Environmental Effects of Marine Renewable Energy Development Around the World. Report for Ocean Energy Systems (OES).
Singh, N., & Davar, S. C. (2004). Noise pollution-sources, effects and control. Journal of Human Ecology, 16(3), 181-187.
Slabbekoorn, H. (2019). Noise pollution. Current Biology, 29(19), 957-960.
Wang, W., Gao, H., Li, C., Deng, Y., Zhou, D., Li, Y., Zhou, W., Luo, B., Liang, H., Liu, W. and Wu, P. (2022). Airport noise disturbs foraging behavior of Japanese pipistrelle bats. Ecology and Evolution, 12(6), e8976.
Cheng Jing Han • February 20, 2023