At the start of the global Covid-19 lockdown, we all marvelled at the photos showing deserted streets and farm animals wandering through once-busy town centres. Not only did the lockdown period provide unique visual spectacles for us to look back on in years to come, but it turns out that there was also an audible effect of Covid-19.

Recent research, carried out by the University of Michigan in the United States, has shown that there was a significant drop in the level of global noise pollution during the initial Covid-19 lockdown period. The researchers, already collecting data in conjunction with technology giants Apple, used information gathered by smartwatches and smartphones used by volunteers in Florida, New York, California and Texas.

Equivalent continuous average exposure data in dB(A) was calculated from measurements collected by Apple Watches. It was then normalised to 8-hour LEX8H exposures, which allowed for direct comparisons of exposures experienced by participants who wore their watches for different lengths of time.

A cougar is pictured in Santiago city centre, Chile. Photo credit: BBC News/Retuers https://www.bbc.co.uk/news/world-52459487

The results showed that there was an overall reduction (across the four states in the study) of 2.6 decibels, which because of the way sound is measured, represents almost a halving in the amount of sound energy experienced (a reduction of 3dB = half the sound energy). For individual states, New York experienced the greatest reduction (3.1dB) and Florida the smallest (2.4dB).

The reduction is noise levels can almost certainly be attributed to the huge reduction in traffic and the closure of businesses. Similar research is being conducted in the UK, thanks to the Quiet Project, which is still currently gathering data.

Although the reduction in noise levels seems small, a 3dB(A) reduction in average noise exposure (which, remember, is a halving of the amount of sound energy) is associated with a lower risk of developing noise-induced hearing loss, which research has shown can lead to mental health conditions. The research also highlights:

Given that the negative impacts of sound on ischemic heart disease, hypertension, and cognitive performance appear to occur at levels well below 70dB(A) LEX8h, the COVID-related reduction in sound exposures among study participants likely represents a meaningful reduction in overall risk of sound-related health effects.

What this means is that the reduction in environmental noise levels during the Covid-19 lockdown was partnered with a lower risk of people developing serious noise-related health conditions, such as cardiovascular disease and stroke. That isn’t to say that these conditions couldn’t be caused by other factors, just that the influence of noise was greatly reduced.

The study reflects on the fact that its research sample is relatively small, so no concrete conclusions can be drawn. However, what the findings highlight is both the impact of noise pollution on people’s health and the wider impact the Covid-19 lockdown had on the environment and its subsequent health implications. Research conducted by the Museum of London during the UK lockdown also draws attention to the relationship between noise and mental health, and the impact the lockdown had on reducing people’s exposure to excessive noise pollution. You can find out more here.