A new night-time noise index has been developed to better measure the effects of environmental noise on sleep, bringing hopes to advance epidemiological noise-related research.
Whether you can sleep through a storm or wake up at the slightest bump in the night, peace and quiet are things we can all appreciate for a good night’s rest. Unfortunately, in today’s world, silent nights have become a privilege as we are constantly surrounded by various noises that keep us awake and alert at night – from buzzing phones and beeping appliances to construction and traffic noises. Though these sounds may seem trivial during the day, they can become surprisingly bothersome and even harmful at night.
During the day-time, 60 to 70 decibels are considered to be within the normal and tolerable sound range for human ears. However, while sleeping at night, our noise tolerance drops to around 40 decibels thus leaving us more vulnerable to sleep disturbance, which can give rise to other chronic health problems like heart failure and diabetes. To this, governing bodies like the World Health Organisation have set policies to limit night-time environmental noise – capped at 45 decibels at the façade areas of buildings. But guidelines established to date are based on noise indices that use average sound level value, which makes them insufficient to measure the full effects of noise on sleep.
To refine present measurements, Associate Professor Junta Tagusari from Hokkaido University’s Graduate School of Engineering has developed a new index for night-time noise. Using data from a 2014 study that documents the sleeping patterns of some 30 residents of Kaneda, Okinawa, he evaluated the impacts of environmental noise on sleep and human health. Okinawa Prefecture houses the Kadena Air Base, an active base for the United States Air Force, making it a suitable location to study the effects of aircraft noise. Around the area, there are more than 100,000 residents whose houses are exposed to aircraft noise. These houses suffered from especially disruptive night noise events that measured up to 100 decibels.
Through extensive research, it was revealed that the main source of noise in the area was flying aircraft. But in the front area of the base, the noise was primarily caused by taxing aircraft noise. When aircraft engines were being repaired and adjusted, 60 decibels of noise could also be heard for several hours at dawn. With these findings, Tagusari was able to develop a novel mathematical formula for the night-time noise index. Since the new index can be applied to any epidemiological noise-related research, Tagusari plans to re-analyse the health of residents around the Kadena Airbase.
In his most recent study, Tagusari reported that the “local residents have been complaining about the aircraft noises occurring frequently, even during night-time.” Due to these vexing noises, he commented that “they took the initiative to ask [his] laboratory to measure aircraft noise and its correlation to their sleep.”
To determine the effects of environmental noise on sleeping quality, he used a vibration-detecting device called Sleep Scan to obtain data on body motility. The device was placed under the mattress of subjects to record any movements made during their sleep. “For a month, not only did we obtain the night-time noise level, we also measured the body motility during sleep of some of the local residents, aged from 20 to 60 years old,” said Tagusari.
Based on the results gathered from his past and most recent research, Tagasuri came up with several solutions to minimise environmental noise sources in residential areas. “Distancing from noise sources would be great, but there are also some promising alternative solutions for cases like this, namely changing the flight schedule,” he suggested. Nevertheless, these suggestions need to be taken up and set in motion.
Residents around the Kadena Airbase have previously appealed to reduce environmental noise. However, they have only received solutions that do not directly address the root cause of the matter, such as compensation payments and soundproofing installations. Disturbed residents of other areas within airbase vicinities have also attempted to voice their concerns to the court and are still continuing to do so.
Considering the prevalent concern of environmental noise, Tagusari intends to continue his research on noise and sleep. At present, he is examining the effects of low-frequency noise produced by wind turbines on the sleep of locals in Wakkanai, Hokkaido. He also hopes to apply his newly formulated night-time noise index to determine the effect of noise exposure on fetal growth and low-birth rate on women across Hokkaido.
“Evaluating and mitigating the health risks posed by noise exposure are required to protect and maintain our healthy lives. Those are the responsibility of researchers and the government,” commented Tagusari.
Source: Hokkaido University