Decibels were developed by Bell Systems labs in the US (named after Alexander Graham Bell), to be able to describe a large variation in numbers. Well, they first developed the Bel, and then divided that system even further, in to tenths of a Bel, or deci-bel. This also explains why the decibel is annotated as ‘dB’ with the capital letter B.
Decibels can be used to describe anything really – where a base or reference value is provided. For instance, the height of a building could be described in decibels. Assuming the building is constructed entirely of brick, from top to bottom, the reference level would be 1 brick course. So if the building has 100 courses of brick to the roof level, we could say the building is 10 x Log (100/1), which is 20 dB. Therefore, the building is 20 dB tall. Of course, we don’t need to do this, as counting the number of courses is easy to do.
In acoustics, we use the decibel scale from 0 dB to around 120 dB to describe differences in sound pressure level relative to the lowest level that human hearing can detect. The alternative would be to present this scale as 2 x 10-5 or 0.00002 Pascals (the lowest level our ears can detect) up to 20 Pascals (‘the threshold of pain’), which is an absolutely huge range of numbers. Hopefully you see now why we use decibels!
Have a look through the gallery below for examples of different sounds – or noises – at different decibel levels.
To find out what differences in sound level might ‘seem like’ to you, take a look at our Knowledge Article ‘5 dB Improvement? Sure, I know What You Mean!‘.
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