There is nothing more annoying than being woken up by a neighbor's leaf blower, weed wacker or the sound of their latest DIY project (those pesky angle grinders are particularly noisy) early in the morning. Especially, if the intrusive sound is emitting high levels of noise on the weekend. Now, just imagine being woken up from your afternoon nap by your friendly neighborhood engineers, setting off explosives in the latest building demolition downtown. 

Civil engineers in Tokyo, Japan revealed in 2015 that demolishing a building could be done producing a noise as quiet as a whisper. Therefore, the project was branded more of a 'dismantling' than a 'demolition'. The Grand Prince Hotel Akasaka in Tokyo City was to be demolished to make way for another, newer luxury hotel. The demolition was done by the Taisei Corporation, who dismantled the 140-meter building in just six months. 

"This technology almost completely saves the people living nearby from noise and air pollution with harmful dust, which is inevitable when you destroy buildings in the traditional way. The level of noise pollution falls down by 90 percent to 20 decibels," said Taisei Corporation employee Hideki Ichihara, responding to media questions outside of the shrinking building at the time of demolition. 

"Can you imagine? Right now, up there, the work is in full swing, but here [down on the ground], it is absolutely unnoticeable," Ichihara concluded. 

The Dean of Engineering at the Engineering Institute of Technology, Steve Mackay, has researched the topic of noise pollution as a result of engineering endeavors. 

"When it comes to reduction in noise, obviously, that's one of the most important things, you want to reduce the level of noise. Machinery manufacturers are very conscious of it. Most countries give you a limit of 85 dba. That or below," Mackay said. 

The measurement of the level of noise the human ear perceives is reflected in the A-weighted decibel, which has been acronymized into dBa. Decibels are just audible at 10dBa. Decibels in everyday situations include:

  • Soft whispering =  30dBA
  • A quiet office = 40dBA
  • Normal talking voice = 65dBA
  • Hand dryers in public restrooms = 80dBA. This is the level at which ear protection becomes necessary.
  • Manufacturing machinery = limit of 85dBA - These are noise levels that can cause damage to ears if continually exposed. Employers whose operations continually reach 85dBA have to secure ear protection for their employees in the form of ear muffs. 
  • A rock concert = 120dBA
  • Thunderclap = 130dBA 

An environmental engineer would surely agree that when it comes to public health, noise pollution is a dangerous threat to a person's wellbeing. It has been well researched and proven that citizens of a country who live near airports have higher blood pressures than those who live elsewhere. People's health directly affected by noisy engineering design. 

The Federal Aviation Authority says that an aircraft's noise output should, at maximum, be 65dBA, observed at ground-level. Gas-powered leaf blowers emit 90 to 102 dBA and generate their own carbon footprint - which has captured the attention of the environmentalists. A town in California named Sonoma, in the United States, has banned the use of gas-powered leaf blowers around the city. Citizens have expressed that they look forward to the "restoration of the quality of life" now that the blowers have been banned. 

Thankfully, thanks to engineering ingenuity, a new battalion of leaf blowers are making their way to the markets - some have already arrived. The leaf blowers are battery operated and only emit 65dBA of noise. The newer blowers will also outclass plug-in blowers due to their wireless capabilities. However, with the cheaper gas alternative, some countries will still stick to the tried-and-tested blowers until proper bans are put in place. 

 More engineering ingenuity is, arguably, needed in all engineering industries, so that noise levels can be driven all the way down.

Steve Mackay tends to agree: "In your next engineering design, think about noise. Think about how to reduce the effect on your wonderful clients. You will probably have a far happier client." 

 

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