9 Dec 2021

What are decibels? (Or how noise affects our health)

¿Qué son los decibelios? (O cómo el ruido afecta nuestra salud),Gráficos por GoodStudio (shutterstock). Image © Eduardo Souza (ArchDaily)

Noisy environments generate extremely negative effects on our bodies and are detrimental to concentration, learning and productivity in classrooms and offices. Headaches are momentary symptoms. However, staying in spaces with high noise levels can bring problems such as hearing loss, affect blood pressure and even damage our digestion. It can also trigger high levels of stress, sleep disorders, mood swings, increased heart rate and ringing in the ear. Noise is an invisible enemy and is part of everyday life in big cities, through heavy traffic, construction or the use of noisy equipment such as generators and air conditioning systems. Although history repeats itself indoors, it is possible to take effective measures to avoid unnecessary noise.

Acoustics

To begin to understand acoustics, there are several concepts and terms that we must understand. It is a very complex science and we only give it due importance when it is not well resolved. Perhaps the best known unit is the decibel (dB). Unlike units such as meters or kilograms, decibels are much more difficult to measure.

Graham Bell

Graham Bell, a Scotsman whose surname was honored with the unit, was the one who noticed that the scale perceived by the ear is logarithmic, just like the Richter Scale, which quantifies the magnitude of an earthquake. This logarithmic scale of sound intensity matches the intensity perceived by the human ear. Since we can hear a very wide range of sound intensities, the limit of audibility, which is 10-12 watts/m2, is taken to be 0 decibels.

 

In other words, there are sounds lower than that, but we cannot hear them. At a frequency of 1000 Hz, the human ear can withstand up to 120 dB without pain. Above this value, sounds are harmful and can irreversibly destroy the structures of the inner ear. Exposure to sound levels above 90 dB for more than 4 hours is already very harmful.

 

The World Health Organization (WHO) uses the value of 55 dB as the ideal maximum noise level to be exposed to most of the time. The institution points out that approximately 20% of the population in European Union countries is exposed to noise above 65 dB (A) during the day, and more than 30% is exposed to levels above 55 dB (A) at night. Exposure to noise of this intensity can trigger sleep disorders and increased blood pressure.

 

To get an idea, a normal conversation is around 60 decibels. This is a reference value, halfway between the limit of audibility and the limit of pain (120 dB). 10 dB is what normal breathing emits. 30 dB refers to a soft whisper, and 50 dB refers to a soothing rain noise. At 60 dB and above, it is necessary to pay attention to prolonged exposure to noise. 85 dB is already equivalent to the noise of a congested street. 110 dB to a crying baby next to you and 120 dB to the intensity of thunder.

See the table below for some reference values:
¿Qué son los decibelios? (O cómo el ruido afecta nuestra salud),© Eduardo Souza (ArchDaily)
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